DETAILED DESCRIPTION OF THE INVENTION

[0028] FIG. 1 illustrates a cross-sectional side view of a reactor, shown generally at 10 , for electrochemical processing of a microelectronic workpiece in accordance with one embodiment the present invention. In the particular embodiment of the invention shown here, the reactor is adapted for electrochemical deposition of a metal, such as copper or copper alloy, on the surface of the microelectronic workpiece. Accordingly, the following description includes express references to elements used in such electrochemical deposition processes. It will be recognized, however, that the reactor architecture is suitable for a wide range of electrochemical processing operations including, for example, anodization of a surface of the workpiece.

[0029] The reactor 10 has a reactor head assembly 20 that assists in supporting the workpiece during processing, and a corresponding processing space in the form of a reactor bowl assembly 30 . Reactor bowl assembly 30 includes one or more walls that define a processing space that contains a processing fluid, as will be set forth in further detail below. This type of reactor assembly is particularly suited for effecting electroplating of semiconductor wafers or like workpieces, in which the wafer is electroplated with a blanket or patterned metallic layer.

[0030] The reactor head assembly 20 and the reactor bowl assembly 30 of the illustrated embodiment may be moved relative to one another. For example, a lift and rotate mechanism, not shown, may be used in conjunction with the head and bowl assemblies 20 , 30 to drive the reactor head 20 in a vertical direction with respect to the reactor bowl assembly 30 and to rotate the reactor head assembly 20 about a horizontally disposed axis. By lifting and rotating the reactor head assembly 20 , a workpiece 45 , such as a semiconductor wafer, may be moved between a load position that allows the workpiece 45 to be placed upon the head assembly 20 , and a processing position in which at least a portion of the workpiece 45 is brought into contact with processing fluid in the processing space of the reactor bowl assembly 30 . When the workpiece is in the processing position, it is generally oriented with the process side down within the processing space. When the workpiece 45 is in the load position, the workpiece 45 is generally exposed outside of the reactor bowl assembly 30 with the process side directed upward, for loading and unloading by, for example, a robotic wafer transfer mechanism. One example of a suitable lift and rotate mechanism is described in connection with U.S. patent application Ser. No. 09/351,980, filed Jul. 12, 1999, entitled “Lift and Rotate Mechanism for Use in a Workpiece Processing Apparatus”, the disclosure of which is incorporated herein by reference.

[0031] Preferably, the reactor head assembly 20 includes a stationary assembly 50 and a rotor assembly 55 The rotor assembly 55 is configured with one or more structures that serve to support the workpiece and to rotate the workpiece 45 about a generally vertical axis during, for example, workpiece processing.

[0032] In the reactor embodiment of FIG. 1 , the workpiece 45 is held in place, with respect to the rotor assembly 55 by contact assembly 60 . In addition to holding the workpiece 45 in place, the contact assembly 60 may include one or more electrical contacts that are disposed to engage the workpiece 45 for applying electrical power used in the electrochemical processing operation. One embodiment of a contact assembly is described in detail in connection with U.S. patent application Ser. No. 09/386,803, filed Aug. 31, 1999, entitled “Method and Apparatus for Processing the Surface of a Microelectronic Workpiece”, the disclosure of which is incorporated herein by reference. It will be recognized, however, that other contact architectures, such as discrete finger contacts or the like, are also suitable depending on the desired electrochemical processing that is to take place in the reactor 10 . One J-hook design described in connection with U.S. patent application Ser. No. 08/680,057, filed Jul. 15, 1996, entitled “Electrode Semiconductor Workpiece Holder”, the disclosure of which is similarly incorporated herein by reference.

[0033] During processing, the workpiece 45 is brought into contact with processing fluid located within the reactor bowl assembly 30 . In the illustrated embodiment, reactor bowl assembly 30 comprises a reactor base assembly 65 that, in turn, includes process cup assembly 75 and an electrode housing assembly 70 . The process cup assembly 75 includes a plurality of wall structures that define a processing space therebetween. The electrode housing assembly 70 is located within the process cup assembly 75 and includes therein an electrode 105 used in electrochemnical processing of a workpiece 45 .

[0034] Generally stated, the processing space within the process cup assembly 75 includes at least two process fluid flow regions. The first fluid flow region is proximate the upper end and interior to the electrode housing assembly 70 while the second flow region includes the region at the upper end of processing cup 75 proximate workpiece 45 . As will be explained in further detail below, processing fluid flow in the first fluid flow region is generally directed toward the interior of the electrode housing assembly 70 and, more particularly, toward a surface of the electrode 105 , and generally away from the workpiece 45 . In contrast, the flow of processing fluid in the second fluid flow region is generally directed toward the workpiece 45 and generally away from electrode 105 . One arrangement of structures that can be used to accomplish this fluid flow pattern is described in detail below.

[0035] The electrode housing assembly 70 of the illustrated embodiment includes a housing member 72 , which is generally bowl shaped and includes an end that is open toward the workpiece 45 . A pressure drop member 90 is disposed over the open end of the housing member 72 . The pressure drop member 90 assists in dividing the processing space into the aforementioned first fluid flow region 95 and second fluid flow region 100 .

[0036] The housing member 72 may have a lip 80 located at the opening or the rim thereof that extends radially inwards and then downward toward the base of the assembly. The lip 80 may have a cross section in the shape of an inverted “u” that defines a space 85 located therein, which extends around the circumference of the electrode housing assembly 70 . The lip 80 may serve as the locus of the engagement between the housing member 72 and the pressure drop member 90 . Together, the housing member 72 and pressure drop member 90 define an interior electrode chamber in which electrode 105 is disposed.

[0037] The pressure drop member 90 may be conically shaped, and have an apex oriented so as to extend downward into the interior electrode chamber. To this end, the pressure drop member 90 may comprise a conically shaped frame 110 , and a permeable membrane 115 that is fixed with the surface of the conically shaped frame 110 . The conically shaped frame 110 is particularly illustrated in FIG. 2 while the conically shaped frame 110 with the membrane 115 fixed thereto is particularly illustrated in FIG. 3 . The membrane 115 may be fluid permeable or only permeable to at least one of the ionic species in the processing fluid. In this latter instance, the reactor may be augmented with separate inlets and outlets respectively associated with each of the fluid flow regions.

[0038] FIG. 2 is an isometric view of the conically shaped frame 110 of the pressure drop member 90 . The conically shaped frame 110 includes a continuous circular base member 120 , and a plurality of ribs 125 which extend between the circular base member 120 and the point 130 of the conical shape. In the frame 110 at the place where the point 130 of the conical shape would be located, the conically shaped frame 110 includes a circular opening 135 . The opening 135 in the frames avoids a large area near the point 130 of the conical shape, which might otherwise trap fluid and/or substantially restrict fluid or current flow.

[0039] Located around the circumference of the circular base member 120 of the conically shaped frame 110 is a protrusion 140 , which extends outward from the circular base member 120 and is adapted for engaging a groove 145 located in the inverted u-shaped lip 80 of the electrode housing assembly 70 (shown more clearly in FIG. 4 ).

[0040] FIG. 3 is an isometric view of the pressure drop member 90 , including the conically shaped frame 110 illustrated in FIG. 2 , with the membrane 115 attached thereto. The membrane 115 may be comprised of a plastic filter type media, or other media that at least partially restricts the flow of processing fluid flow therethrough. The membrane 115 also assists in preventing larger size particulates, precipitates, and/or gas bubbles from crossing the pressure drop member 90 and entering the second fluid flow region.

[0041] The membrane 115 is preferably formed into a conical shape, by cutting a triangular pie-shaped notch in the membrane material. The resulting edges formed by the triangular shaped notch may then be joined and held together with, for example, a single ultrasonic weld seam 150 . The membrane 115 is then attached to the conical shaped frame 110 using a similar ultrasonic weld along the ribs 125 and the continuous perimeter of the circular base member 120 .

[0042] The circular base member 120 , ribs 125 and membrane 115 are preferably formed from polypropylene, polyethylene, polyvinylidene fluoride, or other fluorocarbon type plastic. Such plastics are generally chemically inert with respect to the processing which is likely to take place in the plating reactor 10 .

[0043] In an alternative embodiment, the pressure drop membrane is formed from a sufficiently resilient membrane which does not require an underlying frame structure.

[0044] Further alternative embodiments include the pressure drop member being formed from a pressed disk of porous ceramic or porous glass.

[0045] Referring back to FIG. 1 , the plating reactor 10 further includes a fluid inlet 155 located within a riser tube 160 near the bottom of the cup assembly 65 for receiving processing fluid. The processing fluid is generally received from a fluid reservoir located external to the plating reactor 10 .

[0046] The processing fluid received via the fluid inlet 155 initially enters the second fluid flow region 100 of the cup assembly 65 via the space 165 formed between the electrode housing assembly 70 and the process cup assembly 75 . The processing fluid generally follows a flow corresponding to the direction of arrows illustrated in FIG. 1 . While in the second fluid flow region 100 , the processing fluid comes into contact with the workpiece 45 when in a processing position.

[0047] By placing the anode 105 in the first fluid flow region 95 within the electrode housing assembly 70 and having the processing fluid enter the cup assembly 65 via the second fluid flow region 100 , the anode 105 is isolated from the fluid flow when the processing fluid initially enters the cup assembly 65 . Correspondingly, the processing fluid does not directly impinge upon the anode 105 , which may be a consumable anode. As a result the useful life of the anode 105 is prolonged.

[0048] In connection with the electrode housing assembly 70 , the plating reactor includes a fluid outlet tube 165 . The fluid outlet tube 165 has an opening 170 , which extends into the space 85 formed within the inverted u-shaped lip 80 of the electrode housing assembly 70 . The addition of processing fluid into second fluid flow region 100 via the fluid inlet 155 and the exit of fluid from the first fluid flow region 95 via the opening 170 in the fluid outlet tube 165 , creates a pressure differential between the first fluid flow region 95 and the second fluid flow region 100 in which the pressure in the first fluid flow region 95 is lower than the pressure in the second fluid flow region 100 . In the upper region of the reactor, fluid will flow from the second fluid flow region 100 into the first fluid flow region 95 through the pressure drop member 90 in an attempt to equalize pressure between the regions.

[0049] The pressure drop member 90 provides some resistance to the flow of fluid across the semi-porous membrane 115 . As such, the pressure equalizing flow of processing fluid is somewhat restricted. Restricting the flow of fluid across the pressure drop member 90 has several effects. For example, the flow of process fluid across the pressure drop member 90 is distributed more evenly along the surface of the pressure drop member 90 . Further, the restricted flow facilitates generation of a pressure differential between the first fluid flow region 95 and the second fluid flow region 100 . Because the pressure in the second fluid flow region 100 is maintained at a level that is slightly higher than the pressure in the first region, fluid flow from the first fluid flow region 95 into the second fluid flow region 100 across the pressure drop member 90 is unlikely. This pressure differential, in turn, effectively restricts passage of any byproducts formed at electrode 105 during the electrochemical reaction to an area within the first fluid flow region 95 and assists in preventing such byproducts from reaching the surface of the workpiece 45 . Rather, the byproducts generated within fluid flow region 95 can be directed from the processing space through the fluid outlet tube 165 . Such an arrangement allows for separate processing of the processing fluid overflowing weir 180 and fluid exiting fluid outlet 165 . Special filtering or processing of the processing fluid exiting the first fluid flow may be employed to particularly remove any of the unwanted byproducts before the processing fluid is mixed and/or processed with the processing fluid overflowing weir 180 for recirculation to the plating reactor 10 via the fluid inlet 155 . As a result, exposure of the workpiece 45 to potentially harmful byproducts produced at the electrode 105 is substantially limited and/or can more easily be controlled using the illustrated reactor architecture.

[0050] Since the pressure drop member 90 is conically shaped and extends downward into the electrode housing assembly 70 , it has a surface at the interior electrode chamber that is oriented at an angle. The angle at which the surface of the pressure drop member is defined so that the highest point of the pressure drop member 90 is proximate to the u-shaped lip 80 of the electrode housing assembly 70 . The angled surface of the pressure drop member directs any particulates, precipitates or gas bubbles formed at the electrode 105 away from the center of the electrode housing assembly toward the periphery and into the space 85 within the u-shaped lip 80 of the electrode housing assembly 70 . Not only does the angled surface of the pressure drop member move the byproducts away from the center of the processing area where they can otherwise adversely affect uniform current flow, the pressure drop member also assists in driving the byproducts toward the opening 170 of the fluid outlet tube 165 . Eventually the particulates, precipitates and/or gas bubbles exit the cup assembly 65 along with the processing fluid via fluid outlet tube 165 . This is more clearly shown in connection with FIG. 4 .

[0051] FIG. 4 illustrates an enlarged cross-sectional view of an upper portion of the electrode housing assembly 70 of FIG. 1 . More particularly, it illustrates the portion of the reactor bowl assembly 30 at which the pressure drop member 90 engages the u-shaped lip 80 of the electrode housing assembly 70 , and also illustrates the fluid outlet tube 165 and the opening 170 that facilitates fluid communication with the space 85 defined by the u-shaped lip 80 . One example of the potential direction of fluid flow exiting the first region 95 via the fluid outlet tube 165 is illustrated by arrow 175 .

[0052] Specifically, the fluid pressure at the opening 170 and inside the fluid outlet tube 165 is lower than the fluid pressure located elsewhere in the cup assembly 65 . This is due in part to the opening 170 of the fluid outlet tube 165 being below the overall level of the processing fluid. As a result of the lower pressure proximate the opening 170 of the fluid outlet tube 165 , fluid will migrate towards the opening 165 from elsewhere in the cup assembly. More specifically, the fluid from the first region will generally migrate towards the space 85 within the U-shaped lip 80 , which extends circumferentially around the outer perimeter of the cup assembly 65 , proximate the opening 170 The fluid then enters the tube 165 via the opening 170 and exits the reactor bowl assembly 30 .

[0053] Although the fluid flow from the first fluid flow region 95 to the second fluid flow region 100 is restricted, charged particles required for electrochemical processing of the workpiece 45 can still flow from the first fluid flow region 95 to the second fluid flow region 100 across the pressure drop member 90 , as charged particles will flow independent of the fluid flow. This is possible if the particles are suitably charged and are sized appropriately to make it through the pressure drop barrier.

[0054] In addition to fluid outlet tube 165 , the processing fluid can further exit the cup assembly 65 via an overflow weir 180 located at the lip of the wall of the process cup assembly 75 . The processing fluid, which has overflowed the overflow weir 180 , can then be drained via a cup drain valve 185 located near the bottom of the reactor bowl assembly 30 .

[0055] In the embodiment illustrated in FIG. 1 , the reactor bowl assembly 30 further provides for one or more mounting connections adapted for receiving one or more field shaping elements at the internal surface thereof near the lip of the wall of the process cup assembly 75 . More specifically, in the preferred embodiment the mounting connections include one or more generally horizontal grooves 190 extending around the circumference of the wall at different elevations.

[0056] Field shaping elements provide for fluid and/or current shaping or tailoring. The field shaping elements mounted in one of the lower generally horizontal grooves 190 further from the workpiece 45 provides for more global shaping or tailoring of the flow of processing fluid and current, while field shaping elements mounted in one of the higher horizontal grooves 190 closer to the workpiece 45 provide for fluid and current shaping in connection with a more specific point on the workpiece 45 .

[0057] In accordance with one embodiment used in the electroplating of copper onto the surface of the workpiece, a consumable phosphorized copper anode and two field shaping elements are used. The field shaping elements include a lower field shaping element 195 or diffuser plate (illustrated in FIG. 5 ) and an upper field shaping element 200 or shield (illustrated in FIG. 6 ).

[0058] FIGS. 5 and 6 are isometric views of two embodiments of field shaping elements 195 , 200 that may be used in the reactor 10 . The field shaping elements 195 , 200 generally each comprise a single plate of material having one or more openings through which plating fluid and/or current is enabled to flow. Depending on the opening pattern a more controlled distribution of plating fluid and current across the surface of the workpiece 45 can be achieved. Although each of these elements is illustrated to include peripherally disposed notches, such notches are optional but may be used to assist in securing the respective elements in place within the reactor assembly in cooperation with other corresponding structures.

[0059] FIG. 5 illustrates a first of the two preferred field shaping elements 195 that may be concurrently used in the reactor bowl assembly 30 . The first field shaping element 195 includes a plurality of openings 205 arranged approximately in a grid like pattern. However, a spiral pattern may also be used. In at least one of the preferred embodiments, the first field shaping element 195 is positioned in one of the lower horizontal grooves 190 .

[0060] FIG. 6 illustrates a second of the two preferred field shaping elements 200 that may be used along with the first field shaping element 195 illustrated in FIG. 5 . The second field shaping element 200 preferably includes a single larger opening 210 approximately centered in the field shaping element 200 . The second field shaping element 200 directs the processing fluid and electrical current away from the edge of the workpiece 45 . In at least one embodiment, the second field shaping element 200 may be positioned proximate to the workpiece 45 in one of the higher horizontal grooves 190 .

[0061] Examples of field shaping elements or diffuser plates, including diffuser plates having alternative opening patterns, are further described in connection with U.S. patent application Ser. No. 09/351,864, filed Jul. 12, 1999, entitled “Diffuser with Spiral Opening Pattern for Electroplating Reactor Vessel”, the disclosure of which is incorporated herein by reference.

[0062] FIG. 7 illustrates an enlarged cross-sectional view of a portion of the plating reactor illustrated in FIG. 1 , further illustrating one particular embodiment where the field shaping elements 195 and 200 , illustrated in FIGS. 5 and 6 , are each present in one of the plurality of horizontal grooves 190 for receiving a field shaping element Specifically, FIG. 7 illustrates the field shaping element 200 or shield (illustrated in FIG. 6 ) in one of the higher horizontal grooves, and the field shaping element 195 or diffuser plate (illustrated in FIG. 5 ) in one of the lower horizontal grooves

[0063] Use of the present invention in an electroplating process is not only envisioned with respect the plating of copper onto a workpiece using a consumable phosphorized anode, but is further envisioned as having utility in any electroplating process where there is a desire to limit exposure of the cathode/workpiece to the products produced at the anode. For example, the above noted electroplating process is further envisioned as having utility in connection with a process for plating nickel onto a workpiece using a consumable nickel sulfur anode, and a process for plating solder onto a workpiece using a consumable tin lead anode, or for anodic processing of a workpiece, in which gas is produced at the cathode.

[0064] Numerous modifications may be made to the foregoing system without departing from the basic teachings thereof. Although the present invention has been described in substantial detail with reference to one or more specific embodiments, those of skill in the art will recognize that changes may be made thereto without departing from the scope and spirit of the invention as set forth in the appended claims.