Chemical mechanical polishing apparatus and chemical mechanical polishing method thereof
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.
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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 INVENTION1. 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
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
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 INVENTIONThe 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.
Referring to
Referring to
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
The chemical mechanical polishing method of the invention is elaborated with the flowchart of
Referring to both
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 EmbodimentReferring to
Referring to both
Referring to
Referring to
Referring to
Referring to
Referring to
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
Firstly, referring to
Next, referring to
Then, referring to
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
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.
Claims
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.
Type: Application
Filed: Jul 29, 2008
Publication Date: Feb 5, 2009
Applicant: National Taiwan University of Science and Technology (Taipei)
Inventors: Chao-Chang Chen (Taipei City), Li-Sheng Hsu (Taipei City)
Application Number: 12/219,800
International Classification: B24B 49/04 (20060101); B24B 29/02 (20060101); B24B 49/08 (20060101);