Title:
Chemical mechanical polishing apparatus and chemical mechanical polishing method thereof
Kind Code:
A1


Abstract:
A chemical mechanical polishing apparatus and a chemical mechanical polishing method thereof are provided. The chemical mechanical polishing method at least includes the following steps. In step a, a positive pressure is formed between a polishing pad and a wafer. In step b, the wafer is driven to revolve around a first central axis. In step c, a polishing slurry is injected between the polishing pad and the wafer. In step d, the positive pressure formed on the wafer by the polishing pad is adjusted for change the contacting modes of the polishing pad and the wafer as well as the wafer removal rate.



Inventors:
Chen, Chao-chang (Taipei City, TW)
Hsu, Li-sheng (Taipei City, TW)
Application Number:
12/219800
Publication Date:
02/05/2009
Filing Date:
07/29/2008
Assignee:
National Taiwan University of Science and Technology (Taipei, TW)
Primary Class:
Other Classes:
451/36, 451/287, 451/288
International Classes:
B24B29/02; B24B49/04; B24B49/08
View Patent Images:



Primary Examiner:
ELEY, TIMOTHY V
Attorney, Agent or Firm:
BACON & THOMAS, PLLC (Alexandria, VA, US)
Claims:
What is claimed is:

1. A chemical mechanical polishing apparatus, comprising: a carrier used for carrying a wafer to revolve around a first central axis; a polishing platen used for pasting a polishing pad thereon, wherein a positive pressure is applied between the polishing pad and the wafer, the polishing platen drives the polishing pad to revolve around a second central axis; a polishing slurry injector for injecting a polishing slurry into the gap between the wafer and the polishing pad; and a controlling unit used for changing the contacting modes of the polishing pad and the wafer as well as the removal rate of the wafer by adjusting the positive pressure formed on the wafer by the polishing pad.

2. The chemical mechanical polishing apparatus according to claim 1, wherein the contacting modes of the polishing pad and the wafer comprise a hydrodynamic-contacting mode, a semi-contacting mode and a full-contacting mode; at the hydrodynamic-contacting mode, the polishing pad and the wafer do not have any contact and the wafer has a first removal rate; at the semi-contacting mode, the polishing pad and the wafer have partial contact and the wafer has a second removal rate; at the full-contacting mode, the polishing pad and the wafer have full contact and the wafer has a third removal rate, wherein the first removal rate is smaller than the second removal rate, and the second removal rate is smaller than the third removal rate.

3. The chemical mechanical polishing apparatus according to claim 1, wherein the controlling unit is used for adjusting the positive pressure by adjusting the gap between the polishing platen and the carrier.

4. The chemical mechanical polishing apparatus according to claim 1, wherein the carrier drives the wafer to revolve at a first rotation rate, the polishing platen drives the polishing pad to revolve at a second rotation rate, and the controlling unit adjusts the relative velocity by adjusting the first rotation rate or the second rotation rate.

5. The chemical mechanical polishing apparatus according to claim 1, wherein a relative velocity is formed between the wafer and the polishing pad, the controlling unit adjusts and the relative velocity during the polishing process.

6. The chemical mechanical polishing apparatus according to claim 1, wherein the wafer comprises an insulating layer made from a low-K material.

7. The chemical mechanical polishing apparatus according to claim 6, wherein the K dielectric value of the low-K material is smaller than 5.

8. The chemical mechanical polishing apparatus according to claim 1, further comprising: a flatness sensor used for sensing the flatness of the wafer; and at least a supplementary polishing platen used for pasting a supplementary polishing pad thereon, the supplementary polishing platen polishes the wafer for supplementation according to the flatness of the wafer.

9. The chemical mechanical polishing apparatus according to claim 1, wherein the wafer adopts copper wire manufacturing process.

10. A chemical mechanical polishing method for polishing a wafer, wherein the chemical mechanical polishing method comprises the following steps: (a) applying a positive pressure between the polishing pad and the wafer; (b) driving the wafer to revolve around a first central axis and driving the polishing pad to revolve around a second central axis; (c) injecting a polishing slurry into the gap between the polishing pad and the wafer; and (d) adjusting the positive pressure formed on the wafer by the polishing pad and for changing the contacting modes of the polishing pad and the wafer as well as the removal rate of the wafer.

11. The chemical mechanical polishing method according to claim 10, wherein the contacting modes of the polishing pad and the wafer comprises a hydrodynamic-contacting mode, a semi-contacting mode and a full-contacting mode; at the hydrodynamic-contacting mode, the polishing pad and the wafer do not have contact and the wafer has a first removal rate; at the semi-contacting mode, the polishing pad and the wafer have partial contact and the wafer has a second removal rate; at the full-contacting mode, the polishing pad and the wafer have full contact and the wafer has a third removal rate, wherein the first removal rate is smaller than the second removal rate, and the second removal rate is smaller than the third removal rate.

12. The chemical mechanical polishing method according to claim 10, wherein in the step (d), the positive pressure is adjusted by adjusting the gap between the polishing platen and the carrier.

13. The chemical mechanical polishing method according to claim 10, wherein in the step (b), a relative velocity is formed between the wafer and the polishing pad, and in the step (d), the relative velocity is adjusted.

14. The chemical mechanical polishing method according to claim 10, wherein in the step (d), the positive pressure and the relative velocity are adjusted at any time during the polishing process.

15. The chemical mechanical polishing method according to claim 10, 5 wherein the wafer has an insulating layer made from a low-K material.

16. The chemical mechanical polishing method according to claim 15, wherein the K dielectric value of the low-K material is smaller than 5.

17. The chemical mechanical polishing method according to claim 10, further comprising: (e) sensing the flatness of the wafer; and (f) polishing the wafer for supplementation according to the flatness of the wafer.

18. The chemical mechanical polishing method according to claim 10, wherein the wafer adopts copper wire manufacturing process.

19. A chemical mechanical polishing apparatus, comprising: a carrier for carrying a wafer, wherein the carrier drives the wafer to revolve around a first central axis, and the wafer has a plurality of wafer sub-regions each having a first thickness; a poishing platen used for pasting a polishing pad thereon, wherein a positive pressure is applied between the polishing pad and each wafer sub-region, the poishing platen drives the polishing pad to revolve around a second central axis, and the polishing pad corresponding to each wafer sub-region has a second thickness which keeps changing along with the rotation of the wafer and the polishing pad; a polishing slurry injector for injecting a polishing slurry between the wafer and the polishing pad; and a controlling unit for adjusting the positive pressure applied to each wafer sub-region by the polishing pad according to the change relationship of between each first and second thickness corresponding to a wafer sub-region so as to change the contacting mode between the polishing pad and the wafer as well as the removal rate of the wafer.

20. The chemical mechanical polishing apparatus according to claim 19, wherein the carrier drives the wafer to revolve around a first rotation rate, the poishing platen drives the polishing pad to revolve around a second rotation rate, and the controlling unit obtains the change relationship of the second thickness of each wafer sub-region according to the first rotation rate and the second rotation rate.

21. A chemical mechanical polishing method for polishing a wafer, wherein the chemical mechanical polishing method at least comprises the following steps: (g) applying a positive pressure between a polishing pad and the wafer, wherein the wafer has a plurality of wafer sub-regions each having a first thickness; (h) driving the wafer to revolve around a first central axis and driving the polishing pad t revolve around a second central axis, wherein the polishing pad corresponding to each wafer sub-region has a second thickness which keeps changing along with the rotation of the wafer and the polishing pad; (i) injecting a polishing slurry between the polishing pad and the wafer; and (j) adjusting the positive pressure applied to each wafer sub-region by the polishing pad according to the change relationship of between each first and second thickness corresponding to a wafer sub-region so as to change the contacting mode between the polishing pad and each wafer sub-region as well as the removal rate of each wafer sub-region.

22. The chemical mechanical polishing method according to claim 21, wherein the step (h) drives the wafer to revolve around a first rotation rate and drives the polishing pad to revolve around a second rotation rate, and the step (j) obtains the change relationship of the second thickness of each wafer sub-region according to the first rotation rate and the second rotation rate.

23. The chemical mechanical polishing method according to claim 22, wherein before the step (g), the chemical mechanical polishing method further comprises: (k) providing an all flat dummy wafer having a plurality of dummy sub-regions each corresponding to a wafer sub-region of the wafer respectively; (l) disposing a plurality of gauges on each dummy sub-region respectively; (m) driving the dummy wafer to revolve around the first central axis and driving the polishing pad to revolve around the second central axis, wherein the polishing pad corresponding to each dummy sub-region has the second thickness, which keeps changing along with the rotation of the dummy wafer and the polishing pad; (n) measuring the change relationship of each second thickness by each gauge; and (o) storing the change relationship of each second thickness.

Description:

This application claims the benefit of Taiwan application Serial No. 96128302, filed Aug. 1, 2007, and Taiwan application Serial No. 97108401, filed Mar. 10, 2008, the subject matter of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates in general to a chemical mechanical polishing apparatus and a chemical mechanical polishing method thereof, and more particularly to a chemical mechanical polishing apparatus for polishing the wafer and a chemical mechanical polishing method thereof.

2. Description of the Related Art

For semiconductor elements, the wire density is increasing but the wire pitch is decreasing, the flatness on the surface of the wafer must be maintained at a certain level. When the difference between the protrusion and the indention on the surface of the wafer is too large, the focusing precision during the optical-lithography manufacturing process will be severely affected. During the optical-lithography manufacturing process, the difference between the protrusion and the indention on the surface of the wafer must be reduced to be within the focal depth of the optical-lithography manufacturing process, so that the pattern of the mask can be accurately mapped on the wafer. Therefore, during the semiconductor manufacturing process, the flattening step is a crucial procedure.

Referring to FIG. 1, a perspective of a conventional chemical mechanical polishing apparatus 900 is shown. The chemical mechanical polishing apparatus 900 includes a polishing platen 910, a carrier 920 and a polishing slurry injector 930. The polishing platen 910 is used for pasting a polishing pad 911 thereon. The carrier 920 is used for carrying a wafer 921. The polishing platen 910 applies a pressure on the wafer 921, so that the polishing pad 911 and the wafer 921 have tight contact. The polishing slurry injector 930 injects a polishing slurry 931 into the gap between the wafer 921 and the polishing pad 911. The polishing slurry 931 is a mixing solution of chemical solution, additive or grinding material. The polishing pad 911 is made from a polymer such as polyurethane through foaming and solidification. The polishing pad 911 has many tiny holes on the surface for storing the polishing slurry 931. During the polishing process, the polishing platen 910 revolves around a first central axis L910, and the carrier 920 revolves around a second central axis L920. With the function of the pressure and the speed, the polishing slurry 931 is capable of removing the erosion layer from the surface of the wafer 921.

However, as the wire density keeps increasing but the wire pitch keeps decreasing, conventional chemical mechanical polishing apparatus 900 and polishing method thereof encounter many problems that are hard to be resolved.

Firstly, there comes dishing effect problem. Referring to FIG. 2, a perspective of dishing effect D and erosion effect E is shown. The overall drawing denotes erosion effect E, while the dotted area denotes dishing effect D. As the wire density is increasing but the wire pitch is decreasing, the RC-delay effect becomes larger. The RC-delay effect reduces signal transmission rate and increases cross talk noise and power consumption. To reduce the RC-delay effect, the aluminum wire manufacturing process is currently replaced by the copper wire manufacturing process. The copper wire 921a has a lower hardness level and is not easy to form a protective oxidation layer. Furthermore, the barrier layer 921b and the copper wire 921a have different removal rates. During the polishing manufacturing process, the copper wire 921a and the barrier layer 921b are often over polished and resulted in dishing effect D.

Secondly, there comes the erosion effect problem. As the wire density increases and the wire pitch decreases, the width of the insulating layer 921c decreases, so that the hardness of the insulating layer 921c decreases. During the polishing manufacturing process, the insulating layer 921c are often over polished and resulted in erosion effect E.

Thirdly, the throughout is decreases. During the polishing manufacturing process, the dishing effect D and the erosion effect E often occur concurrently, largely affecting the defect rate of the product. The current solution is to reduce the pressure (approximately 1˜3 psi) of the wafer 921 formed from the polishing pad 911, so as to reduce the dishing effect D and the erosion effect E. However, the decrease in pressure will cause the material removal rate to decrease, despite partial flatness is increased but the throughout is reduced.

Fourthly, manufacturing process is difficult to be integrated. To reduce the RC-delay effect, the aluminum wire manufacturing process by the copper wire manufacturing process, the insulating layer 931c is made from a low-K material in addition to replacing the aluminum wire manufacturing process by the copper wire manufacturing process. However, the low-K material has low stiffness, low fracture to ugliness, low hardness and instability. If silicate is added to increase the hardness of the low-K material, the fracture to ugliness will be reduced. For chemical mechanical polishing manufacturing process, the fracture to ugliness must be larger than the friction generated during the polishing process. Normally, the low-K material cannot resist high temperature and has a high thermal expansion coefficient. Therefore, during the polishing manufacturing process, the low-K material is likely to be adhered onto hetero material and results in detachment.

Fifthly, the yield rate decreases and cost increases. Conventional chemical mechanical polishing apparatus 900 and the polishing method thereof often result in defected products which cannot be repaired and are wasted, not only reducing the yield rate but also increasing manufacturing cost.

SUMMARY OF THE INVENTION

The invention is directed to a chemical mechanical polishing apparatus and a chemical mechanical polishing method thereof. By way of adjusting the positive pressure, the chemical mechanical polishing apparatus and the chemical mechanical polishing method thereof at least have the advantages of avoiding dishing effect and erosion effect and preventing the low-K material and the copper material from being detached.

According to a first aspect of the present invention, a chemical mechanical polishing apparatus is provided. The chemical mechanical polishing apparatus includes a carrier, a polishing platen, a polishing slurry injector and a controlling unit. The carrier is used for carrying and driving a wafer to revolve around a first central axis. The polishing platen is used for pasting a polishing pad, drives the polishing pad to apply a positive pressure on the wafer and drives the polishing pad revolve around a second central axis. The polishing slurry injector is used for injecting a polishing slurry into the gap between the wafer and the polishing pad. The controlling unit is used for adjusting the positive pressure formed on the wafer by the polishing pad for changing the three contacting modes of the polishing pad and the wafer. The three contacting modes are hydrodynamic-contacting mode, semi-contacting mode, and full-contacting mode. Different contacting modes are selected according to the variety of materials on the wafer for adjusting the removal rate on the surface of the wafer. Therefore, the wafer is polished through the balance between the hydrodynamic pressure field and the positive pressure on the polishing pad.

According to a second aspect of the present invention, a chemical mechanical polishing method is provided. The chemical mechanical polishing method at least includes the following steps. In step a, a polishing pad is driven to from a positive pressure on the wafer. In step b, the wafer is driven to revolve around a first central axis, and the polishing pad is driven to revolve around a second central axis. In step c, a polishing slurry is injected into the gap between the polishing pad and the wafer. In step d, the positive pressure formed on the wafer by the polishing pad is adjusted for changing the contacting modes of the polishing pad and the wafer as well as the removal rate of the wafer. The wafer is polished through the balance between the hydrodynamic pressure field and the positive pressure formed on the polishing pad. Examples of the input parameters of the method includes rotation rates of the polishing pad, the wafer and the polishing platen, the positive pressure formed on the wafer by the polishing pad, and the gap between the wafer and the polishing pad, and examples of the output parameters include the hydrodynamic pressure, the positive pressure formed on the wafer by the polishing pad, and the shear stress.

The invention will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 (Prior Art) is a perspective of a conventional chemical mechanical polishing apparatus;

FIG. 2 (Prior Art) is a perspective of dishing effect and erosion effect;

FIG. 3 is a perspective of a chemical mechanical polishing apparatus according to a first embodiment of the invention;

FIG. 4 is a perspective of the polishing pad of FIG. 3 and a wafer in a smaller hydrodynamic pressure field with smaller positive pressure;

FIG. 5 is a perspective of the polishing pad perspective of FIG. 4 and a wafer in larger hydrodynamic pressure field P with larger positive pressure F;

FIG. 6 is a flowchart of a chemical mechanical polishing method according to a first embodiment of the invention;

FIG. 7 is a perspective of a chemical mechanical polishing apparatus according to a second embodiment of the invention;

FIG. 8 is a flowchart of a chemical mechanical polishing method according to a second embodiment of the invention.

FIG. 9 is a perspective of the chemical mechanical polishing apparatus 300 according to a third embodiment of the invention;

FIG. 10A is a top view of the wafer 311;

FIG. 10B is a side view of the wafer 311;

FIGS. 11A˜11B are various side views of the wafer 311 and the polishing pad 321;

FIG. 12A is a relationship curve of the change of the second thickness d21(t) corresponding to wafer sub-region W1;

FIG. 12B is a relationship curve of the change of the second thickness d22(t) corresponding to wafer sub-region W2;

FIG. 13 is a flowchart of chemical mechanical polishing method according to a third embodiment of the invention;

FIG. 14 is a perspective of the all-flat dummy wafer 800;

FIG. 15 is a perspective of the step 1303 of FIG. 13; and

FIG. 16 is a perspective of the step 1305 of FIG. 13.

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment

Referring to FIG. 3, a perspective of a chemical mechanical polishing apparatus 100 according to a first embodiment of the invention is shown. The chemical mechanical polishing apparatus 100 includes a carrier 110, a polishing platen 120, a polishing slurry injector 130 and a controlling unit 140. The carrier 110 used for carrying a wafer 111 drives the wafer 111 to revolve around a first central axis L110. The polishing platen 120 is used for pasting a polishing pad 121 thereon. In the present embodiment of the invention, the polishing platen 120 is located underneath the carrier 110 and is larger than the carrier 110. A positive pressure F is applied between the carrier 110 and the polishing platen 120 for enabling the polishing pad 121 and the wafer 111 to contact each other tightly. The polishing platen 120 drives the polishing pad 121 to revolve around a second central axis L120. Generally speaking, the polishing pad 121 and the carrier 110 are rotated in opposite directions. The rotation of the carrier 110 and the polishing pad 121 generate a relative velocity VR between the wafer 111 and the polishing pad 121. The polishing slurry injector 130 injects a polishing slurry 131 into the gap between the wafer 111 and the polishing pad 121 for performing the polishing process.

Referring to FIG. 4, a perspective of the polishing pad 121 of FIG. 3 and a wafer 111 in a smaller hydrodynamic pressure field with smaller positive pressure F is shown. The polishing slurry 131 forms a hydrodynamic pressure field P via a relative velocity VR. The hydrodynamic pressure field P is distributed on the wafer 111 for polishing the wafer 111. As indicated in FIG. 3, the controlling unit 140 is used for adjusting the positive pressure F and the relative velocity VR affecting the hydrodynamic pressure field P.

During the polishing process, the wafer 111 receives the positive pressure F formed by the polishing pad 121 and the hydrodynamic pressure field P.

Referring to FIG. 5, a perspective of the polishing pad 121 of FIG. 3 and a wafer 111 in a larger hydrodynamic pressure field with larger positive pressure F is shown. The current trend is that the wire density is increasing and the wire pitch is decreasing. Despite the wafer 111 adopts copper wire manufacturing process, the width of the insulating layer of the wafer 111 decreases, or the insulating layer of the wafer 111 is made from a low-K material, when the polishing platen 120 has a higher rotation rate and generates a larger hydrodynamic pressure field P, the contact surface between the copper wire or the insulating layer and the surface of polishing pad 121 is decreased, so that the positive pressure F and friction are decreased. As a result, over polishing or damage is avoided, dishing effect and erosion effect are decreased, and the detachment of the insulating layer is avoided. The k value of the low-K material is not for limiting the scope of application of the invention. In the present embodiment of the invention, a dielectric material whose K value is smaller than 5 is defined as a low-K material.

The chemical mechanical polishing method of the invention is elaborated with the flowchart of FIG. 6 and above structures.

Referring to both FIG. 6 and FIG. 3. FIG. 6 is a flowchart of a chemical mechanical polishing method according to a first embodiment of the invention. The chemical mechanical polishing method at least includes the following steps. Firstly, the method begins at step 601, a positive pressure F is applied between the polishing pad 121 and the wafer 111. Generally speaking, the heavier the polishing pad 121 is pressed, the larger the positive pressure F is formed on the wafer 111. In other words, the smaller the gap G between the polishing platen 120 and the carrier 110 will be, the heavier the polishing pad 121 is pressed and the larger the positive pressure F will be. To the contrary, the larger the G between the polishing platen 120 and the carrier 110 is, the lighter the polishing pad 120 is pressed, and the smaller the positive pressure F will be.

Meanwhile, the carrier 110 drives the wafer 111 to revolve around a first central axis L110, and the polishing platen 120 drives the polishing pad 121 to revolve around a second central axis L120, so that a relative velocity VR is formed between the wafer 111 and the polishing pad 121. The carrier 110 drives the wafer 111 to revolve at a first rotation rate V1. The polishing platen 120 drives the polishing pad 121 to revolve at a second rotation rate V121. The first rotation rate V1 and the second rotation rate V121 directly affect the magnitude of the relative velocity VR.

Moreover, a polishing slurry injector 130 is injected between the polishing pad 121 and the wafer 111. As disclosed above, the polishing slurry 131 forms a hydrodynamic pressure field P via a relative velocity VR. In the polishing process, the change of the relative velocity VR will change the hydrodynamic pressure field P.

Next, the method proceeds to step 602, the controlling unit 140 adjusts the magnitudes of the positive pressure F and the relative velocity VR, thereby changing the contacting modes of the polishing pad 121 and the wafer 111 as well as the removal rate of the wafer 111.

There are at least three contacting modes between the polishing pad 121 and 111 the wafer.

(1) At the hydrodynamic-contacting mode, the polishing pad 121 and the wafer 111 do not have any contact and the wafer 111 has a first removal rate;

(2) At the semi-contacting mode, the polishing pad 121 and the wafer 111 have partial contact and the wafer 111 has a second removal rate;

(3) At the full-contacting mode, the polishing pad 121 and the wafer 111 have complete contact and the wafer 111 has a third removal rate.

At the above contacting modes, the first removal rate<the second removal rate<the third removal rate. During the polishing process, the contacting modes of the wafer and the polishing pad can be changed as the hydrodynamic-contacting mode, the semi-contacting mode or the full-contacting mode by adjusting the positive pressure F and the relative velocity VR affecting the hydrodynamic pressure field P. The three contacting modes correspond to three different removal rates, during the polishing process, the removal rate can be adjusted according to different needs.

The method of adjusting the positive pressure F includes adjusting the gap G between the polishing platen 120 and the carrier 110 or increasing the stress on the polishing platen 120 or the carrier 110. The method of adjusting the relative velocity VR includes adjusting the first rotation rate V1 1 or the second rotation rate V121.

As disclosed above, the controlling unit 140 can adjust the positive pressure F and the relative velocity VR at any time during the polishing process so that the wafer 111 receives a uniformed hydrodynamic pressure field P and generates an equivalent deformation.

Besides, when the wafer 111 has severe dishing effect D and erosion effect E, the controlling unit 140 still can obtain a larger removal rate by decreasing the positive pressure F and increasing the relative velocity VR and the hydrodynamic pressure field P. Thus, the wafer 111 not only avoids the dishing effect D and the erosion effect E occurring during the polishing process but also maintains the removal rate at a certain level.

Second Embodiment

Referring to FIG. 7, a perspective of a chemical mechanical polishing apparatus 200 according to a second embodiment of the invention is shown. The chemical mechanical polishing apparatus 200 of the present embodiment of the invention differs with the chemical mechanical polishing apparatus 100 of the first embodiment in that the chemical mechanical polishing apparatus 200 further includes a flatness sensor 250 and at least a supplementary polishing platen 260. The supplementary polishing platen 260 is used for pasting a supplementary polishing pad 261 thereon. In the present embodiment of the invention, the carrier 210 and the wafer 211 are disposed at the bottom while the polishing platen 220, the polishing pad 221, the supplementary polishing platen 260 and the supplementary polishing pad 261 are disposed at the top. As for other similarities, the same designations are used and are not repeated here.

Referring to both FIG. 7 and FIG. 8. FIG. 8 is a flowchart of a chemical mechanical polishing method according to a second embodiment of the invention. The chemical mechanical polishing method further includes step 803 and step 804. In step 803, the flatness sensor 250 senses the flatness of the wafer 211. In step 804, the supplementary polishing platen 260 supplementally polishes the wafer 211 for supplementation according to the flatness of the wafer 211. The supplementary polishing platen 260 polishes the wafer with respect to the uneven part of the wafer 211 only. Thus, full-range flatness is achieved without over polishing any partial part of the wafer.

Third Embodiment

Referring to FIG. 9, a perspective of the chemical mechanical polishing apparatus 300 according to a third embodiment of the invention is shown. The carrier 310 drives the wafer 311 to revolve at a first rotation rate V311, and the poishing platen 320 drives the polishing pad 321 to revolve at a second rotation rate V321.

Referring to FIG. 10A and FIG. 10B. FIG. 10A is a top view of the wafer 311. FIG. 10B is a side view of the wafer 311. As indicated in FIG. 10A, the wafer 311 has N wafer sub-regions Wi′i=1˜N. As indicated in FIG. 10B, each wafer sub-region Wi has a first thickness d1i′i=1˜N. As the surface of the wafer 311 is not even, the first thickness d1i′i=1˜N is not identical.

Referring to FIGS. 11A-11B, various side views of the wafer 311 and the polishing pad 321 are shown. During the rotation of the wafer 311 and the polishing pad 321, the position at which a wafer sub-region Wi′i=1˜N contacts the polishing pad 321 keeps changing. At a particular time t, the polishing pad corresponding to the wafer sub-region Wi′i=1˜N has a second thickness d2i(t)′i=1˜N. For example, in FIG. 11A and FIG. 11B, the wafer sub-regions Wi correspond to the same first thickness d1i but to different second thickness d2i(t).

Referring to FIG. 12A, a relationship curve of the change of the second thickness d21(t) corresponding to the wafer sub-region W1 is shown. At time t=1, the position at which the wafer sub-region W1 corresponds to the polishing pad has a second thickness d21(1). At time t=8.5, the position at which the wafer sub-region W1 corresponds to the polishing pad has a second thickness d21(8.5). At time t=10.7, the position at which the wafer sub-region W1 corresponds to the polishing pad has a second thickness d21(10.7). That is, along with the rotation of the wafer 311 and the polishing pad 321, the second thickness d21(t) corresponding to the wafer sub-region W1 keeps changing.

Referring to FIG. 12B, a relationship curve of the change of the second thickness d22(t) corresponding to wafer sub-region W2 is shown. The second thickness d22(t) corresponding to the wafer sub-region W2 also keeps changing. By the same token, the relationship curve of the change of the N second thicknesses d2i(t)′i=1˜N corresponding to the N wafer sub-regions Wi′i=1˜N is obtained.

During the polishing process, the controlling unit 340 adjusts a positive pressure Fi′i=1˜N applied to a wafer sub-region Wi′i =1˜N by the polishing pad 321 according to each first thickness d1i′i=1˜N and second thickness d2i(t)′i=1˜N corresponding to the wafer sub-region Wi′i=1˜N, so as to change the contacting mode between the polishing pad 321 and the wafer sub-region Wi′i=1˜N as well as the removal rate of the wafer sub-region Wi′i=1˜N.

Referring to FIG. 13, a flowchart of chemical mechanical polishing method according to a third embodiment of the invention is shown.

Firstly, referring to FIG. 14, a perspective of the all-flat dummy wafer 800 is shown. In the step 1301, an all-flat a dummy wafer 800 is provided, wherein the dummy wafer 800 has a plurality of dummy sub-regions each corresponding to a wafer sub-region Wi′i=1˜N of the wafer 311.

Next, referring to FIG. 14, in the step 1302, a plurality of sensors Si′i=1˜N are disposed in each dummy sub-region W*i′i=1˜N.

Then, referring to FIG. 15, a perspective of the step 1303 of FIG. 13 is shown. In the step 1303, the dummy wafer is driven to revolve around a first central axis L310 and the polishing pad 321 is driven to revolve around a second central axis L320. As each dummy sub-region W*i′i=1˜N corresponds to a wafer sub-region Wi′i=1˜N, the polishing pad 321 corresponding to the dummy sub-region W*i′i=1˜N also has the second thickness d2i(t)′i=1˜N. Along with the rotation of the dummy wafer 800 and the polishing pad 321, the second thickness d2i(t)′i=1˜N corresponding to the dummy sub-region W*i′i=1˜N keeps changing.

Meanwhile, in the step 1303, the change relationship of the second thickness d2i(t)′i=1˜N is measured by a sensor Si′i=1˜N in advance.

Then, in the step 1304, the change relationship of the second thickness d2i(t)′i=1˜N is stored.

Next, referring to FIG. 16, a perspective of the step 1305 of FIG. 13 is shown. In the step 1305, the wafer 311 is placed on the carrier 310 and a positive pressure Fi′i=1˜N is applied between the polishing pad 321 and the wafer 311.

Meanwhile, in the step 1305, the wafer 311 is driven to revolve around the first central axis L310 and the polishing pad 321 is driven to revolve around the second central axis L320.

Meanwhile, in the step 1305, a polishing slurry 131 is injected between the polishing pad 321 and the wafer 311.

Next, in the step 1306, the positive pressure Fi′i=1˜N applied to a wafer sub-region Wi′i=1˜N by the polishing pad is adjusted according to the change relationship of each first thickness d1i′i=1˜N and second thicknesses d2i(t)′i=1˜N corresponding to th wafer sub-region Wi′i=1˜N so as to change the contacting mode between the polishing pad and the wafer sub-region Wi′i=1˜N as well as the removal rate of the wafer sub-region Wi′i=1˜N.

That is, the change relationship of each second thicknesses d2i(t)′i=1˜N of the present embodiment of the invention can be measured in advance by a dummy wafer 800 and stored accordingly. The change relationship of the second thickness d2i(t)′i=1˜N has much to do with the selection of the polishing pad 321 but is irrelevant to the selection of the wafer 311. Thus, when the polishing process is applied to different wafers 3311, as long as the polishing pad 321 is the same, the operator can adopt the same change relationship of the second thickness d2i(t)′i=1˜N.

Despite the change relationship of the second thickness d2i(t)′i=1˜N is obtained by way of measurement in the above embodiments, the implementation of the invention is not limited thereto. For example, the controlling unit can also obtain the change relationship of the second thickness d2i(t)′i=1˜N of the wafer sub-region Wi′i=1˜N according to the first rotation rate or the second rotation rate.

The chemical mechanical polishing apparatus and the chemical mechanical polishing method thereof disclosed in the above embodiments of the invention adopt the way of adjusting the positive pressure, hence having many advantages. Some of the many advantages are disclosed below:

Firstly, dishing effect is avoided. During the polishing process, a uniformed hydrodynamic pressure field can be achieved by adjusting the positive pressure. Despite the wafer adopts copper wire, during the polishing process of the wafer, the copper wire and the barrier layer are not likely to be over polished. Therefore, the invention effectively avoids dishing effect.

Secondly, erosion effect is avoided. Under the trend that the wire density increases and the wire pitch decreases, despite the width of the insulating layer decreases, during the polishing process, a uniformed hydrodynamic pressure field is not likely to over polish the insulating layer. Therefore, the invention effectively avoids erosion effect.

Thirdly, the low-K material and the copper material are prevented from peeling off the wafer. The three different contacting modes can be changed by adjusting the positive pressure. During the polishing process, the adjustment of the removal rate is based on the material type. For the low-K material and the copper material which are easily adhered on the polishing pad, the adherence between the polishing pad and the low-K material and the copper material is reduced, hence avoiding the low-K material and the copper material from peeling off the wafer.

While the invention has been described by way of example and in terms of a preferred embodiment, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.