Title:

Tuning electrodes used in a reactor for electrochemically processing a microelectronic workpiece

Document Type and Number:

United States Patent Application 20020139678

Kind Code:

Abstract:

A facility for selecting and refining electrical parameters for processing a microelectronic workpiece in a processing chamber is described. The facility initially configures the electrical parameters in accordance with either a mathematical model of the processing chamber or experimental data derived from operating the actual processing chamber. After a workpiece is processed with the initial parameter configuration, the results are measured and a sensitivity matrix based upon the mathematical model of the processing chamber is used to select new parameters that correct for any deficiencies measured in the processing of the first workpiece. These parameters are then used in processing a second workpiece, which may be similarly measured, and the results used to further refine the parameters. In some embodiments, the facility analyzes a profile of the seed layer applied to a workpiece, and determines and communicates to a material deposition tool a set of control parameters designed to deposit material on the workpiece in a manner that compensates for deficiencies in the seed layer.

Inventors:

Wilson, Gregory J. (Kalispell, MT, US)
Mchugh, Paul R. (Kalispell, MT, US)
Weaver, Robert A. (Whitefish, MT, US)
Ritzdorf, Thomas L. (Bigfork, MT, US)

Plaque It!

We claim:

1. A method in a computing system for controlling an electroplating process in which a sequence of workpieces are electroplated with a material each in an electroplating cycle, such controlling including designating, for each electroplated workpiece, currents supplied to each of a plurality of electroplating anodes, comprising: constructing a Jacobian sensitivity matrix characterizing the effects on plated material thickness at each of a plurality of workpiece positions of varying the currents supplied each of the plurality of anodes; receiving a specification of target plating material thickness at each of the plurality of workpiece positions; applying the Jacobian sensitivity matrix to make a first determination of how a baseline set of anode currents should be varied to produce the specified target plating material thicknesses rather than baseline plating material thicknesses indicated to result from the baseline set of anode currents; generating an indication to conduct a first electroplating cycle with respect to a first workpiece using a designated set of anode currents produced by varying the baseline set of anode currents in accordance with the first determination; receiving measured plating material thicknesses thickness at each of the plurality of workpiece positions of the first workpiece; applying the Jacobian sensitivity matrix to make a second determination of how the set of anode currents designated for the first electroplating cycle should be varied to produce the specified target plating material thicknesses rather than measured plating material thicknesses of the first workpiece; and generating an indication to conduct a second electroplating cycle with respect to a second workpiece using a designated set of anode currents produced by varying the set of anode currents designated for the first electroplating cycle in accordance with the second determination.

2. The method of claim 1, further comprising: receiving measured plating material thicknesses at each of the plurality of workpiece positions from the second electroplating cycle; determining that the measured plating material thicknesses from the second electroplating cycle are within a specified tolerance of the specified target plating material thicknesses; and in response to the determination, generating one or more indications to conduct a plurality of further electroplating cycles using the set of anode currents designated for the second electroplating cycle.

3. The method of claim 1, further comprising: receiving measured plating material thicknesses at each of the plurality of workpiece positions from the second electroplating cycle; applying the Jacobian sensitivity matrix to make a third determination of how the set of anode currents designated for the second electroplating cycle should be varied to produce the specified target plating material thicknesses rather than measured plating material thicknesses of the second workpiece; and generating an indication to conduct a third electroplating cycle using a designated set of anode currents produced by varying the set of anode currents designated for the second electroplating cycle in accordance with the second determination.

4. The method of claim 1, further comprising: before the first electroplating cycle, receiving measured seed layer thicknesses of the first workpiece at each of the plurality of workpiece positions; and before the second electroplating cycle, receiving measured seed layer thicknesses of the second workpiece at each of the plurality of workpiece positions, and wherein the second determination made by applying the Jacobian sensitivity matrix is a determination of how the set of anode currents designated for the first electroplating cycle should be varied to produce the specified target plating material thicknesses rather than measured plating material thicknesses of the first workpiece in light of the differences between the measured seed layer thicknesses of the first and second workpieces.

5. The method of claim 1 wherein the Jacobian sensitivity matrix is generated from a mathematical model of the electroplating process.

6. The method of claim 1 wherein the Jacobian sensitivity matrix is generated from data obtained by operating the electroplating process.

7. The method of claim 1 wherein the baseline plating material thicknesses are generated from data obtained by simulating operation of the electroplating process using a mathematical model of the electroplating process, the simulation using the baseline anode currents.

8. The method of claim 1 wherein the baseline plating material thicknesses are generated from data obtained by operating the electroplating process with the baseline anode currents.

9. A method in a computing system for providing closed-loop control of a process for applying a coating material to a series of workpieces to produce a coating layer of the coating material, comprising: (a) receiving a coating profile specifying one or more attributes of the coating layer to be produced on the workpieces; (b) designating a first set of coating parameters for use in coating a first workpiece; (c) identifying a first set of discrepancies between attributes of the coating layer produced on the first workpiece using the first set of coating parameters and the attributes specified by the coating profile; (d) determining a first set of modifications to the first set of coating parameters expected to reduce the identified first set of discrepancies; (e) modifying the first set of coating parameters in accordance with the determined first set of modifications to produce a second set of coating parameters; (f) designating the second set of coating parameters for use in coating a second workpiece; and (g) repeating (c)-(f) for subsequent workpieces in the series until the identified set of discrepancies falls within a selected tolerance.

10. The method of claim 9, further comprising, after (g), designating the most recently-produced set of coating parameters for use in coating subsequent workpieces.

11. The method of claim 9 wherein each workpiece is a silicon wafer.

12. The method of claim 9 wherein the coating material is a conductor.

13. The method of claim 9 wherein the coating material is copper.

14. The method of claim 9 wherein the process is performed in an electrolysis chamber having a plurality of anodes, and wherein at least a portion of the coating parameters are currents to transmit through identified anodes among the plurality of anodes.

15. The method of claim 9 wherein at least a portion of the attributes of the coating layer to be produced on the workpieces specified by the coating profile are target thicknesses of the coating layer in selected regions on the workpiece.

16. The method of claim 15 wherein the discrepancies identified in (c) correspond to differences between thicknesses measured in the selected regions on the coated workpiece and the target thicknesses specified by the coating profile for the selected regions on the workpiece.

17. The method of claim 15, further comprising: generating a set of predicted coating thicknesses in the selected regions on the first workpiece based upon the first set of coating parameters; receiving an indication of thicknesses measured in the selected regions on the coated first workpiece; computing a difference between the predicted coating thicknesses and the indicated measured thicknesses; and subtracting the computed difference from the determined first set of modifications before using the first set of modifications to modify the first set of coating parameters.

18. The method of claim 15 wherein each of the workpieces bears a seed layer, the method further comprising: for each the first and second workpieces, receiving an indication of seed layer thicknesses measured in the selected regions on the workpiece before the workpiece is coated; and before designating the second set of coating parameters for use in coating a second workpiece, further adjusting the second set of coating parameters in to adjust for differences between the measured thicknesses of the first and second workpieces.

19. The method of claim 9 wherein the coating process is electrolytic deposition.

20. The method of claim 9 wherein the coating process is electrophoretic deposition.

21. The method of claim 9 wherein the coating process is chemical vapor deposition.

22. The method of claim 9 wherein the coating process is physical vapor deposition.

23. The method of claim 9 wherein the coating process is electron beam atomization.

24. The method of claim 9 wherein (d) utilizes a sensitivity matrix mapping changes in attributes to changes in coating parameters expected to produce those attribute changes.

25. A computer-readable medium whose contents cause a computing system to provide closed-loop control of a process for applying a coating material to a series of workpieces to produce a coating layer of the coating material by: (a) receiving a coating profile specifying one or more attributes of the coating layer to be produced on the workpieces; (b) designating a first set of coating parameters for use in coating a first workpiece; (c) identifying a first set of discrepancies between attributes of the coating layer produced on the first workpiece using the first set of coating parameters and the attributes specified by the coating profile; (d) determining a first set of modifications to the first set of coating parameters expected to reduce the identified first set of discrepancies; (e) modifying the first set of coating parameters in accordance with the determined first set of modifications to produce a second set of coating parameters; and (f) designating the second set of coating parameters for use in coating a second workpiece.

26. The computer-readable medium of claim 25, further comprising repeating (c)-(f) for subsequent workpieces in the series until the identified set of discrepancies falls within a selected tolerance.

27. A method in a computing system for automatically configuring parameters controlling operation of a deposition chamber to deposit material on each of a sequence of at least two wafers to improve conformity with a specified deposition pattern, comprising: for each of the sequence of wafers, measuring thicknesses of the wafer before material is deposited on the wafer; for each of the sequence of wafers, measuring thicknesses of the wafer after material is deposited on the wafer; for each of the sequence of wafers after the first wafer of the sequence, configuring the parameters for depositing material on the wafer based on the specified deposition pattern, the measured thickness of the current wafer before material is deposited on the current wafer, the measured thickness of the previous wafer in the sequence before material is deposited on the previous wafer, the parameters used for depositing material on the previous wafer, and the measured thicknesses of the previous wafer after material is deposited on the previous wafer.

28. The method of claim 27 wherein the specified deposition pattern is a flat deposition pattern.

29. The method of claim 27 wherein the specified deposition pattern is a concave deposition pattern.

30. The method of claim 27 wherein the specified deposition pattern is a convex deposition pattern.

31. The method of claim 27 wherein the specified deposition pattern is an arbitrary radial profile.

32. The method of claim 27 wherein the specified deposition pattern is an arbitrary profile.

33. The method of claim 27, further comprising, for a second deposition chamber: retrieving a set of offset values characterizing differences between the deposition chamber and the second deposition chamber; modifying the parameters most recently configured for the deposition chamber in accordance with the retrieved set of offset values to obtain a parameters for the second deposition chamber; and configuring the second deposition chamber with the obtained parameters for the second deposition chamber.

34. An apparatus for automatically configuring parameters controlling operation of a deposition chamber to deposit material on each of a sequence of wafers to improve conformity with a specified deposition pattern, comprising: a pre-deposition measuring subsystem that measures thicknesses of each of the sequence of wafers before material is deposited on the wafer; a post-deposition measuring subsystem that measures thicknesses of each of the sequence of wafers after material is deposited on the wafer; a parameter configuration subsystem that configures the parameters for depositing material on each of the sequence of wafers after the first wafer of the sequence based on the specified deposition pattern, the measured thickness of the current wafer before material is deposited on the current wafer, the measured thickness of the previous wafer in the sequence before material is deposited on the previous wafer, the parameters used for depositing material on the previous wafer, and the measured thicknesses of the previous wafer after material is deposited on the previous wafer.

35. A method in a computing system for constructing a sensitivity matrix usable to adjust currents for a plurality of electrodes in an electroplating chamber to improve plating uniformity, comprising: for each of a plurality of radii on the plating workpiece, obtaining a plating thickness on the workpiece at that radius when a set of baseline currents are delivered through the electrodes; for each of the electrodes, for each of a plurality of plating workpiece radii, obtaining a plating thickness on the workpiece at that radius when the baseline currents are perturbed for that electrode; and constructing a matrix, a first dimension of the matrix corresponding to the plurality of electrodes, a second dimension of the matrix corresponding to the plurality of radii, each entry for a particular electrode and a particular radius being determined by subtracting the thickness at that radius when the baseline currents are delivered through the electrodes from the thickness at that radius when the baseline currents are perturbed for that electrode, then dividing by the magnitude by which that the current for that electrode was perturbed from its baseline current.

36. The method of claim 35 wherein the current for each electrode is perturbed by approximately +0.05 amps.

37. The method of claim 35 wherein the current for each electrode is perturbed by a factor in the range between 1% and 10%.

38. The method of claim 35 wherein the obtained thicknesses are obtained by executing a simulation of the operation of the electroplating chamber based upon a mathematical model of the electroplating chamber.

39. The method of claim 35 wherein the obtained thicknesses are obtained by measuring workpieces plated in the electroplating chamber.

40. The method of claim 35, further comprising repeating the method to produce additional sensitivity matrices for a variety of different conditions.

41. The method of claim 35, further comprising using the constructed sensitivity matrix to modify for use in plating a second workpiece currents used to plate a first workpiece, such that the modified currents cause the second workpiece to be plated more uniformly than the first workpiece.

42. One or more computer memories collectively containing a sensitivity matrix data structure relating to a deposition chamber having a plurality of deposition initiators for depositing material on a workpiece having selected radii, a control parameter being associated with each of the deposition initiators, the data structure comprising a plurality of quantitative entries, each of the entries predicting, for a given change in the control parameter associated with a given deposition initiator, the expected change in deposited material thickness at a given radius, such that the contents of the data structure may be used to determine revised deposition initiator parameters for better conforming deposited material thicknesses to a target profile for deposited material thicknesses.

43. The computer memories of claim 42 wherein the deposition initiators are electrodes, and wherein the control parameters associated with the deposition initiators are currents delivered through the electrodes.

44. The computer memories of claim 42 wherein the sensitivity matrix data structure is a Jacobian sensitivity matrix.

45. The computer memories of claim 42 wherein the computer memories contain multiple sensitivity matrix data structures, each adapted to a different set of conditions.

46. One or more computer memories collectively containing a data structure for controlling a material deposition process, comprising a set of parameter values used in the material deposition process, the parameters having been generated by adjusting an earlier-used set of parameters to resolve differences between measurements of a workpiece deposited using the earlier-used set of parameters and a target deposition profile specified for the deposition process, such that the contents of the data structure may be used to deposit an additional workpiece in greater conformance with the specified deposition profile.

47. The computer memories of claim 46 wherein the deposition process utilizes a plurality of electrodes, and wherein each parameter value of the set is an amount of current to be delivered through one of the plurality of electrodes.

48. One or more computer memories collectively containing a deposition chamber offset data structure, comprising a set of values indicating how to adjust a first parameter set used to obtain acceptable deposition results in a first deposition chamber to produce a second parameter set usable to obtain acceptable deposition results in a second deposition chamber.

49. A reactor for electrochemically processing a microelectronic workpiece comprising: a fluid chamber configured to contain an electrochemical processing fluid; a plurality of electrodes in the fluid chamber; a workpiece holder positionable to hold the microelectronic workpiece in the fluid chamber; an electrical power supply connected to the surface of the microelectronic workpiece and to the plurality of electrodes, at least two of the plurality of electrodes being independently connected to the electrical power supply to facilitate independent supply of power thereto; and a control system connected to the electrical power supply to control at least one electrical power parameter respectively associated with each of the independently connected electrodes, the control system setting the at least one electrical power parameter for a given one of the independently connected electrodes based on one or more inputted parameters and a plurality of predetermined sensitivity values, the predetermined sensitivity values corresponding to process perturbations resulting from perturbations of the electrical power parameter for the given one of the independently connected electrodes.

50. The reactor of claim 49 wherein the at least one electrical parameter is electrical current.

51. The reactor of claim 49 wherein the sensitivity values are logically arranged within the control system as one or more Jacobian matrices.

52. The reactor of claim 49 wherein the at least one user input parameter comprises the thickness of a film that is to be electrochemically deposited on the at least one surface of the microelectronic workpiece.

53. The reactor of claim 49 wherein the independently connected electrodes are arranged concentrically with respect to one another.

54. The reactor of claim 49 wherein the independently connected electrodes are disposed at the same effective distance from the microelectronic workpiece.

55. The reactor of claim 54 wherein the independently connected electrodes are arranged concentrically with respect to one another.

56. The reactor of claim 49 wherein at least two of the independently connected electrodes are disposed at different effective distances from the surface of the microelectronic workpiece.

57. The reactor of claim 56 wherein the independently connected electrodes are arranged concentrically with respect to one another.

58. The reactor of claim 57 wherein the independently connected electrodes are arranged at increasing distances from the microelectronic workpiece from an outermost one of the plurality of concentric anodes to an innermost one of the independently connected electrodes.

59. The reactor of claim 49 wherein one or more of the independently connected electrodes is a virtual electrode.

60. A method in a computing system for controlling an electroplating process having multiple steps in an electroplating chamber having a plurality of electrodes, comprising: for each electrode, determining the net plating charge delivered through the electrode during a first plating cycle to plate a first workpiece by summing the plating charges delivered through the electrode in each step of the process; comparing a plating profile achieved in plating the first workpiece to a target plating profile to identify deviations between the achieved plating profile and the target plating profile; determining new net plating charges for each electrode selected to reduce the identified deviations in a second workpiece; for each new plating charge, distributing the new net plating charge across the steps of the process; using the distributed new net plating charges to determine a current for each electrode for each step of the process; and conducting a second plating cycle to plate a second workpiece, using the currents determined for each electrode for each step.

61. The method of claim 60 wherein the new net plating charges are distributed uniformly across all of the steps of the process.

62. The method of claim 60 wherein the new net plating charges are distributed across the steps of the process by distributing differences between the new net plating charge and the delivered net plating charge to a single step of the process.

63. The method of claim 60 wherein the distributing includes distributing the new net plating charges to each of two or more phases of a selected one of the steps of the process.

64. The method of step 60, further comprising repeating the method to further reduce deviations between the achieved plating profile and the target plating profile.

65. The method of step 60 wherein a sensitivity matrix is used to determine the new net plating charges.

66. The method of step 60 wherein a different sensitivity matrix is used to determine a new net plating charge for each step of the process.

67. A method in a computer system for evaluating a design for an electroplating reactor, comprising: applying to a set of initial electrode currents a mathematical model embodying the reactor design to determine a first resulting plating profile; comparing the first resulting plating profile to a target plating profile to obtain a first difference; applying a sensitivity technique to identify a set of revised electrode currents; applying the mathematical model to the set of revised electrode currents to determine a second resulting plating profile; comparing the second resulting plating profile to the target plating profile to obtain a second difference; and evaluating the design based on the obtained second difference.

68. An apparatus for automatically selecting parameters for using in controlling operation of a deposition chamber to deposit material on a selected wafer to optimize conformity with a specified deposition pattern, comprising: a measurement receiving subsystem that receives: pre-deposition thicknesses of the selected wafer before material is deposited on the wafer; post-deposition thicknesses of an already-deposited wafer after material is deposited on the already-deposited wafer; and pre-deposition thicknesses of the already-deposited wafer before material is deposited on the wafer; and a parameter selection subsystem that selects the parameters to be used to deposit material on the selected wafer based on the specified deposition pattern, the pre-deposition thicknesses of the selected wafer, the pre-deposition thicknesses of the already-deposited wafer, parameters used for depositing material on the already-deposited wafer, and the post-deposition thicknesses of the already-deposited wafer.

69. The apparatus of claim 68, further comprising a deposition chamber for depositing material on the selected wafer using the parameters selected by the parameter selection subsystem.

70. The apparatus of claim 68, further comprising a memory containing a sensitivity matrix used by the parameter selection subsystem in selecting parameters to be used to deposit material on the selected wafer.

71. A method in a computing system for automatically configuring parameters usable to control operation of a deposition chamber to deposit material on a selected wafer to optimize conformity with a specified deposition pattern, comprising: receiving pre-deposition thicknesses of the selected wafer before material is deposited on the wafer; receiving post-deposition thicknesses of an already-deposited wafer after material is deposited on the already-deposited wafer; and receiving pre-deposition thicknesses of the already-deposited wafer before material is deposited on the wafer; selecting the parameters to be used to deposit material on the selected wafer based on the specified deposition pattern, the pre-deposition thicknesses of the selected wafer, the pre-deposition thicknesses of the already-deposited wafer, parameters used for depositing material on the already-deposited wafer, and the post-deposition thicknesses of the already-deposited wafer.

72. The method of claim 71, further comprising controlling a deposition chamber to deposit material on the selected wafer using the selected parameters.

73. The method of claim 71 wherein a sensitivity matrix is used in selecting parameters to be used to deposit material on the selected wafer.

74. A reactor for electrochemically processing a microelectronic workpiece comprising: a fluid chamber configured to contain an electrochemical processing fluid; a plurality of electrodes in the fluid chamber; a workpiece holder positionable to hold the microelectronic workpiece in the fluid chamber; and an electrical power supply connected to the surface of the microelectronic workpiece and to the plurality of electrodes, at least two of the plurality of electrodes being independently connected to the electrical power supply to facilitate independent supply of power thereto, the power supply configured to provide power to each independently connected electrode in accordance with an electrical power parameter provided for the independently connected electrode, each electrical power parameter being based on one or more inputted parameters and a plurality of predetermined sensitivity values, the predetermined sensitivity values corresponding to process perturbations resulting from perturbations of the electrical power parameter for the given one of the independently connected electrodes.

75. The reactor of claim 74 wherein each electrical power parameter is a current level.

76. The reactor of claim 74, further comprising an electrical power parameter selection subsystem that selects the electrical power parameter corresponding to each independently connected electrode.

77. An method for electroplating a selected surface using a plurality of electrodes, comprising: obtaining a current specification set comprised of a plurality of current levels each specified for a particular one of the plurality of electrodes, the current levels of the current specification set comprising a modification of current levels of a distinguished current specification set in order to improve results produced by electroplating in accordance with the distinguished current specification set; and for each electrode, delivering the current level specified for the electrode by the current specification set to the electrode in order to electroplate the selected surface.

78. The method of claim 77 wherein the current specification set is obtained by receiving it via an interface.

79. The method of claim 78 wherein the interface is a user interface.

80. The method of claim 78 wherein the interface is a removable media drive.

81. The method of claim 78 wherein the interface is a network connection.

82. The method of claim 77 wherein the current specification set is obtained by modifying the distinguished current specification set.

83. A method for processing a microelectronic workpiece, comprising: (a) applying a seed layer to the workpiece using a physical vapor deposition process; (b) measuring non-uniformity of the applied seed layer using a metrology device; (c) correcting the measured non-uniformity of the applied seed layer in an multiple-electrode reactor whose electrodes are operated in accordance with electrical parameters determined based on the measured non-uniformity of the applied seed layer and characteristics of the multiple-electrode reactor.

84. The method of claim 83, further comprising, after (c): (d) subjecting the workpiece to an electroless ion plating process in order to enhance the seed layer.

85. The method of claim 84, further comprising, after (d): measuring the thickness of the enhanced seed layer using a metrology device; and depositing a bulk metal layer atop the seed layer in an multiple-electrode reactor whose electrodes are operated in accordance with electrical parameters determined based on the measured thickness of the enhanced seed layer and characteristics of the multiple-electrode reactor.

86. A method for processing microelectronic workpieces, comprising: (a) applying a seed layer to a first workpiece using a first physical vapor deposition tool; (b) applying a seed layer to a second workpiece using a second physical vapor deposition tool; (c) measuring non-uniformity of the seed layer applied to the first workpiece using a metrology device; (d) measuring non-uniformity of the seed layer applied to the second workpiece using a metrology device; (e) correcting the measured non-uniformity of the seed layer applied to the first workpiece in a first multiple-electrode reactor whose electrodes are operated in accordance with electrical parameters determined based on the measured non-uniformity of the seed layer applied to the first workpiece and characteristics of the first multiple-electrode reactor (f) correcting the measured non-uniformity of the seed layer applied to the second workpiece in a second multiple-electrode reactor whose electrodes are operated in accordance with electrical parameters determined based on the measured non-uniformity of the seed layer applied to the second workpiece and characteristics of the second multiple-electrode reactor.

87. The method of claim 86, further comprising, after (f): measuring the thickness of the corrected seed layer of the first workpiece using a metrology device; depositing a bulk metal layer atop the seed layer of the first workpiece in a third multiple-electrode reactor whose electrodes are operated in accordance with electrical parameters determined based on the measured thickness of the corrected seed layer of the first workpiece and characteristics of the third multiple-electrode reactor; measuring the thickness of the corrected seed layer of the second workpiece using a metrology device; depositing a bulk metal layer atop the seed layer of the second workpiece in a third multiple-electrode reactor whose electrodes are operated in accordance with electrical parameters determined based on the measured thickness of the corrected seed layer of the second workpiece and characteristics of the third multiple-electrode reactor.

88. A method for constructing a library of deposition process parameter sets for use in controlling a material deposition tool in which multiple control points are controlled in order to control material deposition, comprising: receiving a plurality of recipes, each recipe identifying a different set of characteristics to be used in performing a deposition process with the tool; for each received recipe, operating the tool in accordance with the recipe, and controlling each of the control points in accordance with an initial parameter set, to deposit a test workpiece; evaluating the deposited test workpiece; identifying deviations between the evaluation of the deposited test workpiece and a target deposition profile; modifying the initial parameter set in a manner projected to reduce the identified deviations; and storing the modified initial parameter set in a manner that associates it with the received recipe.

89. The method of claim 88, further comprising: selecting one of the plurality of recipes; in response to the recipe selection, retrieving the parameter set associated with the selected recipe; and operating the tool in accordance with the selected recipe, and controlling each of the control points in accordance with the retrieved parameter set, to deposit a workpiece.

90. The method of claim 88 wherein the control points of the deposition tool are electrodes, and wherein each initial and modified parameter set specifies a manner of controlling each of the electrodes.

91. One or more computer memories collectively containing a plurality of deposition process parameter sets for use in controlling a material deposition tool in which multiple control points are controlled in order to control material deposition, each parameter set being associated with a processing recipe and containing a parameters specifying how to control each of the control points when performing the processing recipe.

92. The computer memories of claim 91 wherein the parameter sets are determined experimentally under computer control.

93. A method for performing material deposition on a workpiece, comprising: selecting one of a plurality of processing recipes; in response to the recipe selection, from a plurality of deposition process parameter sets determined experimentally under computer control, retrieving a parameter set associated with the selected recipe; and operating a deposition tool in accordance with the selected recipe, and controlling each of a plurality of control points of the tool in accordance with the retrieved parameter set, to deposit a workpiece.

94. One or more computer memories collectively containing an electroplating current data structure, the data structure comprising information specifying, for each of a plurality of seed layer resistivity ranges, a set of currents to be delivered to a group of electrodes in order to electroplate a workpiece having a seed layer whose resistivity falls within the range.

95. The computer memories of claim 94 wherein the sets of currents specified by information in the data structure are experimentally determined under computer control.

96. A method in a computing system for automatically configuring parameters usable to control operation of a reaction chamber to electropolish a selected wafer to optimize conformity with a specified electropolishing pattern, comprising: receiving pre-polishing thicknesses of the selected wafer before the selected wafer is polished; receiving post-polishing thicknesses of an already-polished wafer after the already-polished wafer is polished; and receiving pre-polishing thicknesses of the already-polished wafer before the already-polished wafer is polished; selecting the parameters to be used to polish the selected wafer based on the specified polishing pattern, the pre-polishing thicknesses of the selected wafer, the pre-polishing thicknesses of the already-polished wafer, parameters used for polishing the already-polished wafer, and the post-polishing thicknesses of the already-polished wafer.

97. A method in a computing system for determining deposition parameters to use in performing material deposition on a workpiece, comprising: receiving thickness measurements at predetermined locations on the workpiece; receiving a deposition profile specifying the pattern in which material is to be deposited on the workpiece; obtaining a starting set of deposition parameters, a starting set of pre-deposition thickness measurements, and a starting set of deposited thicknesses corresponding to the starting sets of deposition parameters and pre-deposition thickness measurements; based upon the received and obtained information, determining a set of deposition parameters to use in performing material deposition on the workpiece.

98. The method of claim 97 wherein the set of deposition parameters to use in performing material deposition on the workpiece is determined using sensitivity techniques.

99. A method in a computing system for electroplating a microelectronic workpiece, comprising: receiving data representing a profile of a seed layer that has been applied to the workpiece; identifying deficiencies in the seed layer based upon the profile of the seed layer represented by the received data; determining a set of control parameters for plating the workpiece in a manner that compensates for the identified deficiencies in the seed layer; and communicating the determined set of control parameters to a plating tool for use in plating the workpiece.

100. The method of claim 99 wherein the determined set of control parameters is, for each of a plurality of electrodes of the plating tool, one or more current levels to be delivered through the electrode.

Description:

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] The present application is a continuation-in-part of U.S. patent application Ser. No. 09/849,505, filed May 4, 2001, which claims the benefit of U.S. Provisional Patent Application No. 60/206,663, filed May 24, 2000, and which is a continuation-in-part of International Patent Application No. PCT/US00/10120, filed Apr. 13, 2000, designating the United States and claiming the benefit of U.S. Provisional Patent Application No. 60/182,160, filed Feb. 14, 2000, No. 60/143,769, filed Jul. 12, 1999, and No. 60/129,055, filed Apr. 13, 1999; and this application claims the benefit of provisional application No. 60/206,663, filed May 24, 2000; the disclosures of each of which are hereby expressly incorporated by reference in their entireties.

FIELD OF THE INVENTION

[0002] The present invention is directed to the field of automatic process control, and, more particularly, to the field of controlling a material deposition process.

BACKGROUND OF THE INVENTION

[0003] The fabrication of microelectronic components from a microelectronic workpiece, such as a semiconductor wafer substrate, polymer substrate, etc., involves a substantial number of processes. For purposes of the present application, a microelectronic workpiece is defined to include a workpiece formed from a substrate upon which microelectronic circuits or components, data storage elements or layers, and/or micro-mechanical elements are formed. There are a number of different processing operations performed on the microelectronic workpiece to fabricate the microelectronic component(s). Such operations include, for example, material deposition, patterning, doping, chemical mechanical polishing, electropolishing, and heat treatment.

[0004] Material deposition processing involves depositing or otherwise forming thin layers of material on the surface of the microelectronic workpiece. Patterning provides selective deposition of a thin layer and/or removal of selected portions of these added layers. Doping of the semiconductor wafer, or similar microelectronic workpiece, is the process of adding impurities known as “dopants” to selected portions of the wafer to alter the electrical characteristics of the substrate material. Heat treatment of the microelectronic workpiece involves heating and/or cooling the workpiece to achieve specific process results. Chemical mechanical polishing involves the removal of material through a combined chemical/mechanical process while electropolishing involves the removal of material from a workpiece surface using electrochemical reactions.

[0005] Numerous processing devices, known as processing “tools,” have been developed to implement one or more of the foregoing processing operations. These tools take on different configurations depending on the type of workpiece used in the fabrication process and the process or processes executed by the tool. One tool configuration, known as the LT-210C™ processing tool and available from Semitool, Inc., of Kalispell, Mont., includes a plurality of microelectronic workpiece processing stations that are serviced by one or more workpiece transfer robots. Several of the workpiece processing stations utilize a workpiece holder and a process bowl or container for implementing wet processing operations. Such wet processing operations include electroplating, etching, cleaning, electroless deposition, electropolishing, etc. In connection with the present invention, it is the electrochemical processing stations used in the LT-210C™ that are noteworthy. Such electrochemical processing stations perform the foregoing electroplating, electropolishing, anodization, etc., of the microelectronic workpiece. It will be recognized that the electrochemical processing system set forth herein is readily adapted to implement each of the foregoing electrochemical processes.

[0006] In accordance with one configuration of the LT-210C™ tool, the electrochemical processing stations include a workpiece holder and a process container that are disposed proximate one another. The workpiece holder and process container are operated to bring the microelectronic workpiece held by the workpiece holder into contact with an electrochemical processing fluid disposed in the process container. When the microelectronic workpiece is positioned in this manner, the workpiece holder and process container form a processing chamber that may be open, enclosed, or substantially enclosed.

[0007] Electroplating and other electrochemical processes have become important in the production of semiconductor integrated circuits and other microelectronic devices from microelectronic workpieces. For example, electroplating is often used in the formation of one or more metal layers on the workpiece. These metal layers are often used to electrically interconnect the various devices of the integrated circuit. Further, the structures formed from the metal layers may constitute microelectronic devices such as read/write heads, etc.

[0008] Electroplated metals typically include copper, nickel, gold, platinum, solder, nickel-iron, etc. Electroplating is generally effected by initial formation of a seed layer on the microelectronic workpiece in the form of a very thin layer of metal, whereby the surface of the microelectronic workpiece is rendered electrically conductive. This electro-conductivity permits subsequent formation of a blanket or patterned layer of the desired metal by electroplating. Subsequent processing, such as chemical mechanical planarization, may be used to remove unwanted portions of the patterned or metal blanket layer formed during electroplating, resulting in the formation of the desired metallized structure.

[0009] Electropolishing of metals at the surface of a workpiece involves the removal of at least some of the metal using an electrochemical process. The electrochemical process is effectively the reverse of the electroplating reaction and is often carried out using the same or similar reactors as electroplating.

[0010] Anodization typically involves oxidizing a thin-film layer at the surface of the workpiece. For example, it may be desirable to selectively oxidize certain portions of a metal layer, such as a Cu layer, to facilitate subsequent removal of the selected portions in a solution that etches the oxidized material faster than the non-oxidized material. Further, anodization may be used to deposit certain materials, such as perovskite materials, onto the surface of the workpiece.

[0011] As the size of various microelectronic circuits and components decreases, there is a corresponding decrease in the manufacturing tolerances that must be met by the manufacturing tools. In connection with the present invention as described below, electrochemical processes must uniformly process the surface of a given microelectronic workpiece. Further, the electrochemical process must meet workpiece-to-workpiece uniformity requirements.

[0012] Electrochemical processes may be conducted in reaction chambers having either a single electrode or multiple electrodes. Where a single-electrode reaction chamber is used, improving the level uniformity achieved by the process often involves manual trial-and-error modifications to the hardware configuration of the reaction chamber. For example, operators of the process may experiment with repositioning or reorienting the electrode, the workpiece, or a baffle separating the electrode from the workpiece, or may modify aspects of a fluid flow within the reaction chamber in attempts to improve the level uniformity achieved by the process.

[0013] In a multiple-electrode reaction chamber, two or more electrodes are arranged in some pattern. Each of the electrodes is connected to an electrical power supply that provides the electrical power used to execute the electrochemical processing operations. Preferably, at least some of the electrodes are connected to different electrical nodes so that the electrical power provided to them by the power supply may be provided independent of the electrical power provided to other electrodes in the array.

[0014] Electrode arrays having a plurality of electrodes facilitate localized control of the electrical parameters used to electrochemically process the microelectronic workpiece. This localized control of the electrical parameters can be used to provide greater uniformity of the electrochemical processing across the surface of the microelectronic workpiece when compared to single electrode systems without necessitating hardware changes. However, determining the electrical parameters for each of the electrodes in the array to achieve the desired process uniformity can be problematic. Typically, the electrical parameter (i.e., electrical current, voltage, etc.) for a given electrode in a given electrochemical process is determined experimentally using a manual trial and error approach. Using such a manual trial and error approach, however, can be very time-consuming. Further, the electrical parameters do not easily translate to other electrochemical processes. For example, a given set of electrical parameters used to electroplate a metal to a thickness X onto the surface of a microelectronic workpiece cannot easily be used to derive the electrical parameters used to electroplate a metal to a thickness Y. Still further, the electrical parameters used to electroplate a desired film thickness X of a given metal (e.g., copper) are generally not suitable for use in electroplating another metal (e.g., platinum). Similar deficiencies in this trial and error approach are associated with other types of electrochemical processes (i.e., anodization, electropolishing, etc.). Also, this manual trial and error approach often must be repeated in several common circumstances, such as when the thickness or level of uniformity of the seed layer changes, when the target plating thickness or profile changes, or when the plating rate changes.

[0015] In view of the foregoing, a system for electrochemically processing a microelectronic workpiece that can be used to automatically identify electrical parameters that cause a multiple electrode array to achieve a high level of uniformity for a wide range of electrochemical processing variables (e.g., seed layer thicknesses, seed layer types, electroplating materials, etc.) would have significant utility.

SUMMARY

[0016] In the following, a facility for automatically identifying electrical parameters that produce a high level of uniformity in electrochemically processing a microelectronic workpiece is described. Embodiments of this facility are adapted to accommodate various electrochemical processes; reactor designs and conditions; plating materials and solutions; workpiece dimensions, materials, and conditions, and the nature and condition of existing coatings on the workpiece. Accordingly, use of the facility may typically result in substantial automation of electrochemical processing, even where a large number of variables in different dimensions are present. Such automation has the capacity to reduce the cost of skilled labor required to oversee a processing operation, as well as increase output quality and throughput. Additionally, use of the facility can both streamline and improve the process of designing new electroplating reactors.

[0017] In one exemplary embodiment, the facility selects and refines electrical parameters for processing a microelectronic workpiece in a processing chamber. The facility initially configures the electrical parameters in accordance with either a mathematical model of the processing chamber or experimental data derived from operating the actual processing chamber. After a workpiece is processed with the initial parameter configuration, the results are measured and a sensitivity matrix based upon the mathematical model of the processing chamber is used to select new parameters that correct for any deficiencies measured in the processing of the first workpiece. These parameters are then used in processing a second workpiece, which may be similarly measured, and the results used to further refine the parameters.

[0018] In another exemplary embodiment, the facility utilizes a sensitivity matrix data structure. The sensitivity matrix data structure relates to a deposition chamber for depositing material on a workpiece. The deposition chamber has a number of deposition initiators, associated with each of which is a control parameter. For example, the deposition chamber may have deposition initiators that are electrodes, whose control parameters are electrical current levels or other control parameters. The data structure contains a number of quantitative entries, each of which predicts, for a given change in the control parameter associated with a given deposition initiator, the expected change in deposited material thickness at a given radius. The contents of this data structure may be used to determine revised deposition initiator parameters for better conforming deposited material thicknesses to a target profile for deposited material thicknesses.

[0019] In another exemplary embodiment, the facility utilizes a material deposition process data structure, which contains a set of parameter values used in a material deposition process. These parameters have been generated by adjusting an earlier-used set of parameters to resolve differences between measurements of a workpiece deposited using the earlier-used set of parameters in a target deposition profile specified for the deposition process. The contents of this data structure may be used to deposit an additional workpiece in great conformance with the specified deposition profile.

[0020] In another exemplary embodiment, the facility controls an electroplating process having multiple steps, which is performed in an electroplating chamber having a number of electrodes. For each electrode, the facility determines the net plating charge delivered through the electrode during a first plating cycle to plate a first workpiece. This is accomplished by summing the plating charges delivered through the electrode in each step of the process. The facility then compares a plating profile achieved in plating the first workpiece to a target plating profile. In such comparison, the facility identifies deviations between the achieved plating profile and the target plating profile. The facility determines new net plating charges for each electrode selected to reduce the identified deviations in the second workpiece. For each of these new net plating charges, the facility distributes the new net plating charge across the steps of the process, and uses the distributed new net plating charges to determine a current for each electrode for each step of the process. A second plating cycle may then be conducted to plate a second workpiece using the currents determined for each electrode for each step.

[0021] In another exemplary embodiment, the facility evaluates a design for an electroplating reactor. The facility first applies a mathematical model embodying the reactor design to a set of initial electrode current to determine a first resulting plating profile. The facility compares the first resulting plating profile to a target plating profile to obtain a first difference. The facility then applies a sensitivity technique to identify a set of revised electrode currents, and applies the mathematical model to the set of revised electrode currents to determine a second resulting plating profile. The facility compares the second resulting plating profile to the target plating profile to obtain a second difference, and evaluates the design based on the obtained second difference.

[0022] In another exemplary embodiment, the facility is embodied in an apparatus for selecting parameters for use in controlling operation of a deposition chamber to deposit material on a selected wafer in a way that optimizes conformity with a specified deposition pattern. The apparatus includes a measurement receiving subsystem that receives the following measurements: pre-deposition thicknesses of the selected wafer before material is deposited on the wafer; post-deposition thicknesses of an already-deposited wafer after material is deposited on the already-deposited wafer; and pre-deposition thicknesses of the already-deposited wafer before material is deposited on the wafer. The apparatus further includes a parameter selection subsystem that selects the parameters to be used to deposit material on the selected wafer based on the specified deposition pattern, the pre-deposition thicknesses of the selected wafer, the pre-deposition thicknesses of the already-deposited wafer, parameters used for depositing material on the already-deposited wafer, and the post-deposition thicknesses of the already-deposited wafer.

[0023] In another exemplary embodiment, the facility electroplates a selected surface using a plurality of electrodes. The facility obtains a current specification set comprised of a plurality of current levels, each specified for a particular one of the plurality of electrodes. The current levels of the current specification set each represent a modification of current levels of a distinguished current specification set, modified in order to improve results produced by electroplating in accordance with the distinguished current specification set. For each electrode, the facility delivers the current level specified for the electrode by the current specification set to the electrode in order to electroplate the selected surface.

[0024] In another exemplary embodiment, the facility automatically configures parameters usable to control operation of a reaction chamber to electropolish a selected wafer in a way that optimizes conformity with a specified electropolishing pattern. The facility receives pre-polishing thicknesses of the selected wafer before the selected wafer is polished. The facility also receives post-polishing thicknesses of an already-polished wafer the already-polished wafer is polished. The facility further receives pre-polishing thicknesses of the already-polished wafer before the already-polished wafer is polished. The facility selects the parameters to polish the selected wafer based on the specified polishing pattern, the pre-polishing thicknesses of the selected wafer, the pre-polishing thicknesses of the already-polished wafer, parameters used for polishing the already-polished wafer, and the post-polishing thicknesses of the already-polished wafer.

[0025] In another exemplary embodiment, the facility electroplates a microelectronic workpiece. The facility receives data representing a profile of a seed layer that has been applied to the workpiece, such as from a metrology station. The facility identifies deficiencies in the seed layer based upon the profile of the seed layer represented by the received data, and determines a set of control parameters for plating the workpiece in a manner that compensates for the identified deficiencies in the seed layer. The facility communicates this determined set of control parameters to a plating tool for use in plating the workpiece.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 is a process schematic diagram showing inputs and outputs of the optimizer.

[0027] FIG. 2 is a process schematic diagram showing a branched correction system utilized by some embodiments of the optimizer.

[0028] FIG. 3 is schematic block diagram of an electrochemical processing system constructed in accordance with one embodiment of the optimizer.

[0029] FIG. 4 is a flowchart illustrating one manner in which the optimizer of FIG. 3 can use a predetermined set of sensitivity values to generate a more accurate electrical parameter set for use in meeting targeted physical characteristics in the processing of a microelectronic workpiece.

[0030] FIG. 5 is a graph of a sample Jacobian sensitivity matrix for a multiple-electrode reaction chamber.

[0031] FIG. 6 is a spreadsheet diagram showing the new current outputs calculated from the inputs for the first optimization run.

[0032] FIG. 7 is a spreadsheet diagram showing the new current outputs calculated from the inputs for the second optimization run.

DETAILED DESCRIPTION

[0033] A facility for automatically selecting and refining electrical parameters for processing a microelectronic workpiece (“the optimizer”) is disclosed. In many embodiments, the optimizer determines process parameters affecting the processing of a round workpiece as a function of processing results at various radii on the workpiece. In some embodiments, the optimizer adjusts the electrode currents for a multiple electrode electroplating chamber, such as multiple anode reaction chambers of the Paragon tool provided by Semitool, Inc. of Kalispell, Montana, in order to achieve a specified thickness profile (i.e., flat, convex, concave, etc.) of a coating, such as a metal or other conductor, applied to a semiconductor wafer. The optimizer adjusts electrode currents for successive workpieces to compensate for changes in the thickness of the seed layer of the incoming workpiece (a source of feed forward control), and/or to correct for non-uniformities produced in prior wafers at the anode currents used to plate them (a source of feedback control). In this way, the optimizer is able to quickly achieve a high level of uniformity in the coating deposited on workpieces without substantial manual intervention.

[0034] The facility typically operates an electroplating chamber containing a principal fluid flow chamber, and a plurality of electrodes disposed in the principal fluid flow chamber. The electroplating chamber typically further contains a workpiece holder positioned to hold at least one surface of the microelectronic workpiece in contact with an electrochemical processing fluid in the principal fluid flow chamber, at least during electrochemical processing of the microelectronic workpiece. One or more electrical contacts are configured to contact the at least one surface of the microelectronic workpiece, and an electrical power supply is connected to the one or more electrical contacts and to the plurality of electrodes. At least two of the plurality of electrodes are independently connected to the electrical power supply to facilitate independent supply of power thereto. The apparatus also includes a control system that is connected to the electrical power supply to control at least one electrical power parameter respectively associated with each of the independently connected electrodes. The control system sets the at least one electrical power parameter for a given one of the independently connected electrodes based on one or more user input parameters and a plurality of predetermined sensitivity values; wherein the sensitivity values correspond to process perturbations resulting from perturbations of the electrical power parameter for the given one of the independently connected electrodes.

[0035] For example, although the present invention is described in the context of electrochemical processing of the microelectronic workpiece, the teachings herein can also be extended to other types of microelectronic workpiece processing. In effect, the teachings herein can be extended to other microelectronic workpiece processing systems that have individually controlled processing elements that are responsive to control parameters and that have interdependent effects on a physical characteristic of the microelectronic workpiece that is processed using the elements. Such systems may employ sensitivity tables or matrices as set forth herein and use them in calculations with one or more input parameters sets to arrive at control parameter values that accurately result in the targeted physical characteristic of the microelectronic workpiece.

[0036] FIG. 1 is a process schematic diagram showing inputs and outputs of the optimizer. FIG. 1 shows that the optimizer 140 uses up to three sources of input: baseline currents 110 , seed change 120 , and thickness error 130 . The baseline currents 110 are the anode currents used to plate the previous wafer or another set of currents for which plating thickness results are known. For the first workpiece in a sequence of workpieces, the baseline currents used to plate the wafer are typically specified by a source other than the optimizer. For example, they may be specified by a recipe used to plate the wafers, or may be manually determined.

[0037] The seed change 120 is the difference between the thickness of the seed layer of the incoming wafer 121 and the thickness of the seed layer of the previous plated wafer 122 . The seed change input 120 is said to be a source of feed-forward control in the optimizer, in that it incorporates information about the upcoming plating cycle, as it reflects the measurement the wafer to be plated in the upcoming plating cycle. Thickness error 130 is the difference in thickness between the previous plated wafer 132 and the target thickness profile 131 specified for the upcoming plating cycle. The thickness error 130 is said to be a source of feedback control, because it incorporates information from an earlier plating cycle, that is, the thickness of the wafer plated in the previous plating cycle.

[0038] FIG. 1 further shows that the optimizer outputs new plating charges 150 for each electrode in the upcoming plating cycle, expressed in amp-minute units. The new plating charges output is combined with a recipe schedule and a current waveform 161 to generate the currents 162 , in amps, to be delivered through each electrode at each point in the recipe schedule. These new currents are used by the plating process to plate a wafer in the next plating cycle. In embodiments in which different types of power supplies are used, other types of control parameters are generated by the optimizer for use in operating the power supply. For example, where a voltage control power supply is used, the control parameters generated by the optimizer are voltages, expressed in volts. The wafer so plated is then subjected to post-plating metrology to measure its plated thickness 132 .

[0039] While the optimizer is shown as receiving inputs and producing outputs at various points in the processing of these values, it will be understood by those in the art that the optimizer may be variously defined to include or exclude aspects of such processing. For example, while FIG. 1 shows the generation of seed change from baseline wafer seed thickness and seed layer thickness outside the optimizer, it is contemplated that such generation may alternatively be performed within the optimizer.

[0040] FIG. 2 is a process schematic diagram showing a branched correction system utilized by some embodiments of the optimizer. The branched adjustment system utilizes two independently-engageable correction adjustments, a feedback adjustment ( 230 , 240 , 272 ) due to thickness errors and a feed forward adjustment ( 220 , 240 , 271 ) due to incoming seed layer thickness variation. When the anode currents produce an acceptable uniformity, the feedback loop may be disengaged from the transformation of baseline currents 210 to new currents 280 . The feed forward compensation may be disengaged in situations where the seed layer variations are not expected to affect thickness uniformity. For example, after the first wafer of a similar batch is corrected for, the feed-forward compensation may be disengaged and the corrections may be applied to each sequential wafer in the batch.

[0041] FIG. 3 is schematic block diagram of an electrochemical processing system constructed in accordance with one embodiment of the optimizer. FIG. 3 shows a reactor assembly 20 for electrochemically processing a microelectronic workpiece 25 , such as a semiconductor wafer, that can be used in connection with the present invention. Generally stated, an embodiment of the reactor assembly 20 includes a reactor head 30 and a corresponding reactor base or container shown generally at 35 . The reactor base 35 can be a bowl and cup assembly for containing a flow of an electrochemical processing solution. The reactor 20 of FIG. 3 can be used to implement a variety of electrochemical processing operations such as electroplating, electropolishing, anodization, etc., as well as to implement a wide variety of other material deposition techniques. For purposes of the following discussion, aspects of the specific embodiment set forth herein will be described, without limitation, in the context of an electroplating process.

[0042] The reactor head 30 of the reactor assembly 20 can include a stationary assembly (not shown) and a rotor assembly (not shown). The rotor assembly may be configured to receive and carry an associated microelectronic workpiece 25 , position the microelectronic workpiece in a process-side down orientation within reactor container 35 , and to rotate or spin the workpiece. The reactor head 30 can also include one or more contacts 85 (shown schematically) that provide electroplating power to the surface of the microelectronic workpiece. In the illustrated embodiment, the contacts 85 are configured to contact a seed layer or other conductive material that is to be plated on the plating surface microelectronic workpiece 25 . It will be recognized, however, that the contacts 85 can engage either the front side or the backside of the workpiece depending upon the appropriate conductive path between the contacts and the area that is to be plated. Suitable reactor heads 30 with contacts 85 are disclosed in U.S. Pat. No. 6,080,291 and U.S. application Ser. Nos. 09/386,803; 09/386,610; 09/386,197; 09/717,927; and 09/823,948, all of which are expressly incorporated herein in their entirety by reference.

[0043] The reactor head 30 can be carried by a lift/rotate apparatus that rotates the reactor head 30 from an upwardly-facing orientation in which it can receive the microelectronic workpiece to a downwardly facing orientation in which the plating surface of the microelectronic workpiece can contact the electroplating solution in reactor base 35 . The lift/rotate apparatus can bring the workpiece 25 into contact with the electroplating solution either coplanar or at a given angle. A robotic system, which can include an end effector, is typically employed for loading/unloading the microelectronic workpiece 25 on the head 30 . It will be recognized that other reactor assembly configurations may be used with the inventive aspects of the disclosed reactor chamber, the foregoing being merely illustrative.

[0044] The reactor base 35 can include an outer overflow container 37 and an interior processing container 39 . A flow of electroplating fluid flows into the processing container 39 through an inlet 42 (arrow I). The electroplating fluid flows through the interior of the processing container 39 and overflows a weir 44 at the top of processing container 39 (arrow F). The fluid overflowing the weir 44 then passes through an overflow container 37 and exits the reactor 20 through an outlet 46 (arrow O). The fluid exiting the outlet 46 may be directed to a recirculation system, chemical replenishment system, disposal system, etc.

[0045] The reactor 20 also includes an electrode in the processing container 39 to contact the electrochemical processing fluid (e.g., the electroplating fluid) as it flows through the reactor 20 . In the embodiment of FIG. 3 , the reactor 20 includes an electrode assembly 50 having a base member 52 through which a plurality of fluid flow apertures 54 extend. The fluid flow apertures 54 assist in disbursing the electroplating fluid flow entering inlet 42 so that the flow of electroplating fluid at the surface of microelectronic workpiece 25 is less localized and has a desired radial distribution. The electrode assembly 50 also includes an electrode array 56 that can comprise a plurality of individual electrodes 58 supported by the base member 52 . The electrode array 56 can have several configurations, including those in which electrodes are disposed at different distances from the microelectronic workpiece. The particular physical configuration that is utilized in a given reactor can depend on the particular type and shape of the microelectronic workpiece 25 . In the illustrated embodiment, the microelectronic workpiece 25 is a disk-shaped semiconductor wafer. Accordingly, the present inventors have found that the individual electrodes 58 may be formed as rings of different diameters and that they may be arranged concentrically in alignment with the center of microelectronic workpiece 25 . It will be recognized, however, that grid arrays or other electrode array configurations may also be employed without departing from the scope of the present invention. One suitable configuration of the reactor base 35 and electrode array 56 is disclosed in U.S. Ser. No. 09/804,696, filed Mar. 12, 2001 (Attorney Docket No. 29195.8119US), while another suitable configuration is disclosed in U.S. Ser. No. 09/804,697, filed Mar. 12, 2001 (Attorney Docket No. 29195.8120US), both of which are hereby incorporated by reference.

[0046] When the reactor 20 electroplates at least one surface of microelectronic workpiece 25 , the plating surface of the workpiece 25 functions as a cathode in the electrochemical reaction and the electrode array 56 functions as an anode. To this end, the plating surface of workpiece 25 is connected to a negative potential terminal of a power supply 60 through contacts 85 and the individual electrodes 58 of the electrode array 56 are connected to positive potential terminals of the supply 60 . In the illustrated embodiment, each of the individual electrodes 58 is connected to a discrete terminal of the supply 60 so that the supply 60 may individually set and/or alter one or more electrical parameters, such as the current flow, associated with each of the individual electrodes 58 . As such, each of the individual electrodes 58 of FIG. 3 is an individually controllable electrode. It will be recognized, however, that one or more of the individual electrodes 58 of the electrode array 56 may be connected to a common node/terminal of the power supply 60 . In such instances, the power supply 60 will alter the one or more electrical parameters of the commonly connected electrodes 58 concurrently, as opposed to individually, thereby effectively making the commonly connected electrodes 58 a single, individually controllable electrode. As such, individually controllable electrodes can be physically distinct electrodes that are connected to discrete terminals of power supply 60 as well as physically distinct electrodes that are commonly connected to a single discrete terminal of power supply 60 . The electrode array 56 preferably comprises at least two individually controllable electrodes.

[0047] The electrode array 56 and the power supply 60 facilitate localized control of the electrical parameters used to electrochemically process the microelectronic workpiece 25 . This localized control of the electrical parameters can be used to enhance the uniformity of the electrochemical processing across the surface of the microelectronic workpiece when compared to a single electrode system. Unfortunately, determining the electrical parameters for each of the electrodes 58 in the array 56 to achieve the desired process uniformity can be difficult. The optimizer, however, simplifies and substantially automates the determination of the electrical parameters associated with each of the individually controllable electrodes. In particular, the optimizer determines a plurality of sensitivity values, either experimentally or through numerical simulation, and subsequently uses the sensitivity values to adjust the electrical parameters associated with each of the individually controllable electrodes. The sensitivity values may be placed in a table or may be in the form of a Jacobian matrix. This table/matrix holds information corresponding to process parameter changes (i.e., thickness of the electroplated film) at various points on the workpiece 25 due to electrical parameter perturbations (i.e., electrical current changes) to each of the individually controllable electrodes. This table/matrix is derived from data from a baseline workpiece plus data from separate runs with a perturbation of a controllable electrical parameter to each of the individually controllable electrode.

[0048] The optimizer typically executes in a control system 65 that is connected to the power supply 60 in order to supply current values for a plating cycle. The control system 65 can take a variety of forms, including general or special-purpose computer systems, either integrated into the manufacturing tool containing the reaction chamber or separate from the manufacturing tool, such as a laptop or other portable computer system. The control system may be communicatively connected to the power supply 60 , or may output current values that are in turn manually inputted to the power supply. Where the control system is connected to the power supply by a network, other computer systems and similar devices may intervene between the control system and the power supply. In many embodiments, the control system contains such components as one or more processors, a primary memory for storing programs and data, a persistent memory for persistently storing programs and data, input/output devices, and a computer-readable medium drive, such as a CD-ROM drive or a DVD drive.

[0049] Once the values for the sensitivity table/matrix have been determined, the values may be stored in and used by control system 65 to control one or more of the electrical parameters that power supply 60 uses in connection with each of the individually controllable electrodes 58 . FIG. 4 is a flow diagram illustrating one manner in which the sensitivity table/matrix may be used to calculate an electrical parameter (i.e., current) for each of the individually controllable electrodes 58 that may be used to meet a process target parameter (i.e., target thickness of the electroplated film).

[0050] In the steps shown in FIG. 4 , the optimizer utilizes two sets of input parameters along with the sensitivity table/matrix to calculate the required electrical parameters. In step 70 , the optimizer performs a first plating cycle (a “test run”) using a known, predetermined set of electrical parameters. For example, a test run can be performed by subjecting a microelectronic workpiece 25 to an electroplating process in which the current provided to each of the individually controllable electrodes 58 is fixed at a predetermined magnitude for a given period of time.

[0051] In step 72 , after the test run is complete, the optimizer measures the physical characteristics (i.e., thickness of the electroplated film) of the test workpiece to produce a first set of parameters. For example, in step 72 , the test workpiece may be subjected to thickness measurements using a metrology station, producing a set of parameters containing thickness measurements at each of a number of points on the test workpiece. In step 74 , the optimizer compares the physical characteristics of the test workpiece measured in step 72 against a second set of input parameters. In the illustrated embodiment of the method, the second set of input parameters corresponds to the target physical characteristics of the microelectronic workpiece that are to be ultimately achieved by the process (i.e., the thickness of the electroplated film). Notably, the target physical characteristics can either be uniform over the surface of the microelectronic workpiece 25 or vary over the surface. For example, in the illustrated embodiment, the thickness of an electroplated film on the surface of the microelectronic workpiece 25 can be used as the target physical characteristic, and the user may expressly specify the target thicknesses at various radial distances from the center of the workpiece, a grid relative to the workpiece, or other reference systems relative to fiducials on the workpiece.

[0052] In step 74 , the optimizer uses the first and second set of input parameters to generate a set of process error values. In step 80 , the optimizer derives a new electrical parameter set based on calculations including the set of process error values and the values of the sensitivity table/matrix. In step 82 , once the new electrical parameter set is derived, the optimizer directs power supply 60 to use the derived electrical parameters in processing the next microelectronic workpiece. Then, in step 404 , the optimizer measures physical characteristics of the test workpiece in a manner similar to step 72 . In step 406 , the optimizer compares the characteristics measured in step 404 with a set of target characteristics to generate a set of process error values. The set of target characteristics may be the same set of target characteristics as used in step 74 , or may be a different set of target characteristics. In step 408 , if the error values generated in step 406 are within a predetermined range, then the optimizer continues in step 410 , else the facility continues in 80 . In step 80 , the optimizer derives a new electrical parameter set. In step 410 , the optimizer uses the newest electrical parameter derived in step 80 in processing subsequent microelectronic workpieces. In some embodiments (not shown), the processed microelectronic workpieces, and/or their measured characteristics are examined, either manually or automatically, in order to further troubleshoot the process.

[0053] With reference again to FIG. 3 , the first and second set of input parameters may be provided to the control system 65 by a user interface 64 and/or a metrics tool 86 . The user interface 64 can include a keyboard, a touch-sensitive screen, a voice recognition system, and/or other input devices. The metrics tool 86 may be an automated tool that is used to measure the physical characteristics of the test workpiece after the test run, such as a metrology station. When both a user interface 64 and a metrics tool 86 are employed, the user interface 64 may be used to input the target physical characteristics that are to be achieved by the process while metrics tool 86 may be used to directly communicate the measured physical characteristics of the test workpiece to the control system 65 . In the absence of a metrics tool that can communicate with control system 65 , the measured physical characteristics of the test workpiece can be provided to control system 65 through the user interface 64 , or by removable data storage media, such as a floppy disk. It will be recognized that the foregoing are only examples of suitable data communications devices and that other data communications devices may be used to provide the first and second set of input parameters to control system 65 .

[0054] In order to predict change in thickness as a function of change in current, the optimizer generates a Jacobian sensitivity matrix. An example in which the sensitivity matrix generated by the optimizer is based upon a mathematical model of the reaction chamber is discussed below. In additional embodiments, however, the sensitivity matrix used by the optimizer is based upon experimental results produced by operating the actual reaction chamber. The data modeled in the sensitivity matrix includes a baseline film thickness profile and as many perturbation curves as anodes, where each perturbation curve involves adding roughly 0.05 amps to one specific anode. The Jacobian is a matrix of partial derivatives, representing the change in thickness in microns over the change in current in amp minutes. Specifically, the Jacobian is an m×n matrix where m, the number of rows, is equal to the number of radial location data points in the modeled data and n, the number of columns, is equal to the number of anodes on the reactor. Typically, the value of m is relatively large (>100) due to the computational mesh chosen for the model of the chamber. The components of the matrix are calculated by taking the quotient of the difference in thickness due to the perturbed anode and the current change in amp-minutes, which is the product of the current change in amps and the run time in minutes.

[0055] As one source of feedback control, the optimizer uses the thickness of the most-recently plated wafer at each of a number of radial positions on the plated wafer. These radial positions may either be selected from the radial positions corresponding to the rows of the matrix, or may be interpolated between the radial positions corresponding to the rows of the matrix. A wide range of numbers of radial positions may be used. As the number of radial positions used increases, the optimizer's results in terms of coating uniformity improves. However, as the number of radial positions used increases, the amount of time required to measure the wafer, to input the measurement results, and/or to operate the optimizer to generate new currents can increase. Accordingly, the smallest number of radial positions that produce acceptable results is typically used. One approach is to use the number of radial test points within a standard metrology contour map (4 for 200 mm and 4 or 6 for 300 mm) plus one, where the extra point is added to better the 3 sigma uniformity for all the points (i.e., to better the diameter scan).

[0056] A specific measurement point map may be designed for the metrology station, which will measure the appropriate points on the wafer corresponding with the radial positions necessary for the optimizer operation.

[0057] The optimizer can further be understood with reference to a specific embodiment in which the electrochemical process is electroplating, the thickness of the electroplated film is the target physical parameter, and the current provided to each of the individually controlled electrodes 58 is the electrical parameter that is to be controlled to achieve the target film thickness. In accordance with this specific embodiment, a Jacobian sensitivity matrix is first derived from experimental or numerically simulated data. FIG. 5 is a graph of a sample Jacobian sensitivity matrix for a multiple-electrode reaction chamber. In particular, FIG. 5 is a graph of a sample change in electroplated film thickness per change in current-time as a function of radial position on the microelectronic workpiece 25 for each of a number of individually controlled electrodes, such as anodes A 1 -A 4 shown in FIG. 3 . A first baseline workpiece is electroplated for a predetermined period of time by delivering a predetermined set of current values to electrodes in the multiple anode reactor. The thickness of the resulting electroplated film is then measured as a function of the radial position on the workpiece. These data points are then used as baseline measurements that are compared to the data acquired as the current to each of the anodes A 1 -A 4 is perturbated. Line 90 is a plot of the Jacobian terms associated with a perturbation in the current provided by power supply 60 to anode A 1 with the current to the remaining anodes A 2 -A 4 held at their constant predetermined values. Line 92 is a plot of the Jacobian terms associated with a perturbation in the current provided by power supply 60 to anode A 2 with the current to the remaining anodes A 1 and A 3 -A 4 held at their constant predetermined values. Line 94 is a plot of the Jacobian terms associated with a perturbation in the current provided by power supply 60 to anode A 3 with the current to the remaining anodes A 1 -A 2 and A 4 held at their constant predetermined values. Lastly, line 96 is a plot of the Jacobian terms associated with a perturbation in the current provided by power supply 60 to anode A 4 with the current to the remaining anodes A 1 -A 3 held at their constant predetermined values.

[0058] The data for the Jacobian parameters shown in FIG. 5 may be computed using the following equations: 1 $\begin{matrix} J_{i j} = \frac{\partial t_{i}}{\partial A M_{j}} ≅ \frac{t_{i} (A M + ɛ_{j}) - t_{i} (A M)}{| ɛ_{j} |} & Equation (A1) \end{matrix}$ embedded image

t(AM)=[t ₁ (AM)t ₂ (AM) . . . t _m (AM)] Equation (A2)

AM=[AM ₁ AM ₂ . . . AM _n ] Equation (A3)

[0059] 2 $\begin{matrix} ɛ_{1} = [\begin{matrix} Δ A M_{1} \\ 0 \\ . \\ . \\ 0 \end{matrix}] ɛ_{2} = [\begin{matrix} 0 \\ Δ A M_{2} \\ 0 \\ . \\ 0 \end{matrix}] \dots ɛ_{n} = [\begin{matrix} 0 \\ . \\ . \\ 0 \\ Δ A M_{n} \end{matrix}] & Equation (A4) \end{matrix}$ embedded image

[0060] where:

[0061] t represents thickness [microns];

[0062] AM represents current [amp-minutes];

[0063] ε represents perturbation [amp-minutes];

[0064] i is an integer corresponding to a radial position on the workpiece;

[0065] j is an integer representing a particular anode;

[0066] m is an integer corresponding to the total number of radial positions on the workpiece; and

[0067] n is an integer representing the total number of individually-controllable anodes.

[0068] The Jacobian sensitivity matrix, set forth below as Equation (A5), is an index of the Jacobian values computed using Equations (A1)-(A4). The Jacobian matrix may be generated either using a simulation of the operation of the deposition chamber based upon a mathematical model of the deposition chamber, or using experimental data derived from the plating of one or more test wafers. Construction of such a mathematical model, as well as its use to simulate operation of the modeled deposition chamber, is discussed in detail in G. Ritter, P. McHugh, G. Wilson and T. Ritzdorf, “Two- and three-dimensional numerical modeling of copper electroplating for advanced ULSI metallization,” Solid State Electronics, volume 44, issue 5, pp. 797-807 (May 2000), available from http://www.elsevier.nl/gej-ng/10/30/25/29/28/27/article.pdf, also available from http://journals.ohiolink.edu/pdflinks/01040215463800982.pdf. 3 $\begin{matrix} J = | \begin{matrix} 0.192982 & 0.071570 & 0.030913 & 0.017811 \\ 0.148448 & 0.084824 & 0.039650 & 0.022264 \\ 0.066126 & 0.087475 & 0.076612 & 0.047073 \\ 0.037112 & 0.057654 & 0.090725 & 0.092239 \\ 0.029689 & 0.045725 & 0.073924 & 0.138040 \end{matrix} | & Equation (A5) \end{matrix}$ embedded image

[0069] The values in the Jacobian matrix are also presented as highlighted data points in the graph of FIG. 5 . These values correspond to the radial positions on the surface of a semiconductor wafer that are typically chosen for measurement. Once the values for the Jacobian sensitivity matrix have been derived, they may be stored in control system 65 for further use.

[0070] Table 1 below sets forth exemplary data corresponding to a test run in which a 200 mm wafer is plated with copper in a multiple anode system using a nominally 2000 Å thick initial copper seed-layer. Identical currents of 1.12 Amps (for 3 minutes) were provided to all four anodes A 1 -A 4 . The resulting thickness at five radial locations was then measured and is recorded in the second column of Table 1. The 3 sigma uniformity of the wafer is 9.4% using a 49 point contour map. Target thickness were then provided and are set forth in column 3 of Table 1. In this example, because a flat coating is desired, the target thickness is the same at each radial position. The thickness errors (processed errors) between the plated film and the target thickness were then calculated and are provided in the last column of Table 1. These calculated thickness errors are used by the optimizer as a source of feedback control. 1

TABLE 1


DATA FROM WAFER PLATED WITH 1.12 AMPS TO
EACH ANODE.
	Radial	Measured	Target
	Location	Thickness	Thickness	Error
	(m)	(microns)	(microns)	(microns)

	0	1.1081	1.0291	−0.0790
	0.032	1.0778	1.0291	−0.0487
	0.063	1.0226	1.0291	0.0065
	0.081	1.0169	1.0291	0.0122
	0.098	0.09987	1.0291	0.0304