Controlling chemical mechanical polishing pad stiffness by adjusting wetting in the backing layer
A polishing pad for a chemical mechanical polishing apparatus includes a polishing layer having a polishing surface and a backing layer formed of a fluid-permeable material. The backing layer includes a lower surface configured to be secured to a platen and an upper surface secured to the polishing layer, wherein the lower surface and upper surface are sealed. A first seal circumferentially seals an edge of the backing layer, and a second seal seals and separates the backing layer into a first region and a second region surrounded by the first region.
1. A polishing pad for a chemical mechanical polishing apparatus, comprising:
a polishing layer of the polishing pad having a polishing surface;
a backing layer of the polishing pad formed of a fluid-permeable material and having a lower surface configured to be secured to a platen and an upper surface secured to the polishing layer; and
a plurality of fluid-impermeable seals including a first seal that circumferentially seals an edge of the backing layer and a second seal that seals and separates the backing layer into a first region and a second region,
wherein the plurality of fluid-impermeable seals extend from the lower surface of the backing layer to the upper surface of the backing layer.
2. The polishing pad of claim 1 , wherein the backing layer has an open-cell structure.
3. The polishing pad of claim 2 , wherein the backing layer comprises a polymer matrix having interconnected voids therein.
4. The polishing pad of claim 1 , wherein at least some of the plurality of fluid-impermeable seals are provided by portions of the backing layer that are impregnated with a sealant material.
5. The polishing pad of claim 1 , wherein at least some of the plurality of fluid-impermeable seals are provided by crimped portions of the backing layer.
6. The polishing pad of claim 1 , wherein the first region surrounds the second region.
7. The polishing pad of claim 6 , wherein the first region and second region are concentric.
8. A chemical mechanical polishing system, comprising:
a platen;
a polishing pad that includes:
a polishing layer having a polishing surface; and
a backing layer formed of a fluid-permeable material and having a lower surface secured by an adhesive layer to the platen and an upper surface secured to the polishing layer;
a plurality of fluid-impermeable seals including a first fluid-impermeable seal that circumferentially seals an edge of the backing layer, and a second fluid- impermeable seal that seals and separates the backing layer into a first region and a second region;
a plurality of vents extending through the platen and the adhesive layer and into the backing layer and configured to permit fluid flow from the platen to the backing layer of the polishing pad; and
a fluid source coupled to the backing layer to direct fluid into the first region and second region of the backing layer.
9. The system of claim 8 , wherein the fluid source is configured to independently control fluid flow into the first region and the second region.
10. The system of claim 9 , wherein the fluid source includes a plurality of independently controllable pumps.
11. The system of claim 8 , comprising a plurality of passages wherein the plurality of vents permit fluid flow into the first region and second region through a plurality of passages.
12. The system of claim 11 , wherein the plurality of vents comprise a material more rigid than a material of the backing layer.
13. The system of claim 11 , wherein the plurality of vents of include a first multiplicity of vents in the first region and a second multiplicity of vents in the second region.
14. The system of claim 13 , wherein the first multiplicity of vents are spaced at equidistant intervals within the first region and the second multiplicity of vents are spaced at equidistant intervals within the second region.
15. The system of claim 8 , wherein at least some of the plurality of fluid-impermeable seals are provided by portions of the backing layer that are impregnated with a sealant material.
16. The system of claim 8 , wherein at least some of the plurality of fluid-impermeable seals are provided by crimped portions of the backing layer.
17. A method of controlling stiffness of a backing layer of a polishing pad in a chemical mechanical polishing system, comprising:
controlling flow of liquid, through a first passage extending from a platen disposed below the polishing pad and into the polishing pad, into a first region of a fluid-permeable backing layer of the polishing pad; and
independently controlling flow of liquid through a second passage, extending from the platen and into the polishing pad, into a second region of the fluid-permeable backing layer that is separated from the first region by a fluid-impermeable seal to control the stiffness of the backing layer by independently managing distribution of the liquid in the first and second regions based on operational parameters.
18. The method of claim 17 , wherein the backing layer has an open-cell structure.
19. The method of claim 17 , wherein the liquid is water.
20. The method of claim 17 , wherein controlling flow of liquid into the first region and second region comprise flowing liquid through vents that project from a platen into the backing layer.