Customized polishing pads for CMP and methods of fabrication and use thereof
View Patent ↗The present application relates to polishing pads for chemical mechanical planarization (CMP) of substrates, and methods of fabrication and use thereof. The pads described in this invention are customized to polishing specifications where specifications include (but not limited to) to the material being polished, chip design and architecture, chip density and pattern density, equipment platform and type of slurry used. These pads can be designed with a specialized polymeric nano-structure with a long or short range order which allows for molecular level tuning achieving superior thermo-mechanical characteristics. More particularly, the pads can be designed and fabricated so that there is both uniform and nonuniform spatial distribution of chemical and physical properties within the pads. In addition, these pads can be designed to tune the coefficient of friction by surface engineering, through the addition of solid lubricants, and creating low shear integral pads having multiple layers of polymeric material which form an interface parallel to the polishing surface. The pads can also have controlled porosity, embedded abrasive, novel grooves on the polishing surface, for slurry transport, which are produced in situ, and a transparent region for endpoint detection.
1. An article comprising a single cast or molded unitary polishing pad for polishing a substrate, wherein said pad has a circular profile and an axis of rotation and is cast in a single mold, said pad comprising a polymer having a property that differs at first and second regions within the pad, wherein the first region has a circular profile about the axis of rotation, wherein the second region has a ring profile and adjoins the first region, said pad providing increased planarity or yield for said substrate when compared to a comparative unitary pad under identical operating conditions that is uniform in regions corresponding to said different regions for said unitary polishing pad but is otherwise identical to said unitary polishing pad.
2. An article according to claim 1 wherein said property is hardness.
3. An article according to claim 2 wherein the first region has a hardness greater than a hardness of the second region.
4. An article according to claim 3 wherein a difference in the hardness of the first region and the second region is at least about 5 Shore D.
5. An article according to claim 4 wherein said difference is at least about 10 Shore D.
6. An article according to claim 3 wherein the circular profile of said pad has an area measure, and said first region occupies at least about 75% of said area measure of the circular profile of said pad.
7. An article according to claim 6 wherein said second region and an interface between said first and second regions occupy said remaining area measure of the circular profile of the pad.
8. An article according to claim 7 wherein said first and second regions are additionally located at a polishing surface of said unitary polishing pad.
9. An article according to claim 8 wherein a difference in the hardness of the first region and the second region is at least about 5 Shore D.
10. An article according to claim 9 wherein said difference is at least about 10 Shore D.
11. An article according to claim 8 wherein the pad further comprises an integral interface within the pad, wherein the interface is parallel to the polishing surface, wherein the interface is formed from at least two polymeric layers, and wherein one of the layers forms the polishing surface.
12. An article according to claim 1 wherein said first and second regions are located at a polishing surface of said unitary polishing pad.
13. An article according to claim 3 wherein first region has a porosity and the second region has a porosity.
14. An article according to claim 13 wherein the second region has a greater porosity than the first region.
15. An article according to claim 1 wherein said property is compressibility.
16. An article according to claim 1 wherein said property is coefficient of restitution.
17. An article according to claim 2 wherein the first region has a hardness less than a hardness of the second region.
18. An article according to claim 3 wherein the pad further comprises an integral interface within the pad, wherein the interface is parallel to the polishing surface, wherein the interface is formed from at least two polymeric layers, and wherein one of the layers forms the polishing surface.
19. An article according to claim 3 wherein the pad contains a solid lubricant in a polishing surface of the pad.
20. An article according to claim 19 wherein the solid lubricant has a coefficient of friction between about 0.0001 and about 0.5.
21. An article according to claim 20 wherein said pad contains in the range of about 0.1-10% by weight of solid lubricant.
22. An article according to claim 3 further comprising a transparent region for endpoint detection.
23. An article according to claim 3 further comprising grooves on the polishing surfaces.
24. An article according to claim 23 wherein the grooves are concentric circular grooves and radiating grooves, wherein the radiating grooves are linear in a first groove region of the radiating grooves and are logarithmic in a second groove region of the radiating grooves, and wherein the concentric circular grooves and the radiating grooves intersect.
25. An article according to claim 24 , wherein the first groove region is closer than the second groove region, to the axis of rotation.
26. An article according to claim 18 , wherein the layers are covalently attached across the integral interface.
27. A method of planarizing a layer of a semiconductor wafer having patterned features that cause high areas and lower areas in said layer, said method comprising contacting the layer with a single cast or molded unitary polishing pad, wherein said pad has a circular profile and an axis of rotation and is cast or molded in a single mold, said pad comprising a polymer having a property that differs at first and second regions within the pad, wherein the first region has a circular profile about the axis of rotation, wherein the second region has a ring profile and adjoins the first region, said pad providing increased planarity or yield for said substrate when compared to a comparative unitary pad under identical operating conditions that is uniform in regions corresponding to said different regions for said unitary polishing pad but is otherwise identical to said unitary polishing pad.
28. The method according to claim 27 wherein the property is hardness.
29. The method according to claim 28 wherein the first region has a hardness greater than the second region.
30. A method according to claim 29 wherein the semiconductor wafer has patterned features that cause high areas and lower areas in said layer.
31. An article according to claim 11 , wherein the layers are covalently attached across the integral interface.
32. An article according to claim 21 wherein the solid lubricant is hexagonal BN.