Multilayer chemical mechanical polishing pad stack with soft and conditionable polishing layer

1. A multilayer chemical mechanical polishing pad stack, comprising:

a polishing layer having a polishing surface, a base surface and an average thickness, T P-avg , measured in a direction perpendicular to the polishing surface from the polishing surface to the base surface; wherein the polishing layer comprises the reaction product of:

a polyfunctional isocyanate, wherein the polyfunctional isocyanate is an isocyanate-terminated urethane prepolymer having 2 to 12 wt % unreacted NCO groups; and

a curative package, comprising:

at least 5 wt % of an amine initiated polyol curative, wherein the amine initiated polyol curative contains at least one nitrogen atom per molecule; wherein the amine initiated polyol curative has an average of at least three hydroxyl groups per molecule;

25 to 95 wt % of a high molecular weight polyol curative, wherein the high molecular weight polyol curative has a number average molecular weight, M N , of 2,500 to 100,000; and wherein the high molecular weight polyol curative has an average of 5 to 7 hydroxyl groups per molecule; and

0 to 70 wt % of a difunctional curative;

wherein the polishing layer exhibits a density of greater than 0.6 g/cm 3 ; a Shore D hardness of 5 to 40; an elongation at break of 100 to 450%; and a cut rate of 25 to 150 μm/hr; and

wherein the polishing layer has a polishing surface adapted for polishing a substrate;

a rigid layer having a top surface and a bottom surface;

a hot melt adhesive interposed between the polishing layer and the top surface of the rigid layer; wherein the hot melt adhesive bonds the polishing layer to the rigid layer;

a pressure sensitive platen adhesive layer having a stack side and a platen side; wherein the stack side of the pressure sensitive platen adhesive layer is adjacent to the bottom surface of the rigid layer; and

optionally, a release liner; wherein the optional release liner is disposed on the platen side of the pressure sensitive platen adhesive layer.

2. The multilayer chemical mechanical polishing pad stack of claim 1 , wherein the top surface of the rigid layer is ungrooved; and wherein the bottom surface of the rigid layer is ungrooved.

3. The multilayer chemical mechanical polishing pad stack of claim 1 , wherein the top surface and the bottom surface of the rigid layer each have a roughness, Ra, of 1 to 500 nm.

4. The multilayer chemical mechanical polishing pad stack of claim 1 , wherein the rigid layer has a Young's Modulus of 2,500 to 7,500 MPa.

5. The multilayer chemical mechanical polishing pad stack of claim 1 , wherein the rigid layer is made of a biaxially oriented polyethylene terephthalate; wherein the rigid layer has an average thickness of 6 to 10 mils; and wherein the rigid layer exhibits a Young's Modulus of 3,000 to 7,000 MPa.

6. The multilayer chemical mechanical polishing pad stack of claim 1 ,

wherein the high molecular weight polyol curative has a number average molecular weight, M N , of 7,500 to 25,000.

7. The multilayer chemical mechanical polishing pad stack of claim 6 , further comprising:

a subpad having a stack surface and a platen surface; and

a stack adhesive interposed between the bottom surface of the rigid layer and the stack surface of the subpad;

wherein the stack adhesive bonds the rigid layer to the subpad and wherein the stack side of the pressure sensitive platen adhesive layer is disposed on the platen surface of the subpad; and

optionally, a window incorporated into the multilayer chemical mechanical polishing pad stack.

8. The multilayer chemical mechanical polishing pad stack of claim 6 ,

wherein the curative package consists of:

5 to 20 wt % of the amine initiated polyol curative, wherein the amine initiated polyol curative contains two nitrogen atoms per molecule; wherein the amine initiated polyol curative has an average of 4 hydroxyl groups per molecule; and wherein the amine initiated polyol curative has a number average molecular weight, M N , of 200 to 400;

50 to 75 wt % of the high molecular weight polyol curative, wherein the high molecular weight polyol curative has a number average molecular weight, M N , of 10,000 to 12,000; and wherein the high molecular weight polyol curative has an average of 6 hydroxyl groups per molecule;

10 to 30 wt % of the difunctional curative; wherein the difunctional curative is a diamine curative selected from the group consisting of

4,4′-methylene-bis-(2-chloroaniline) (MBOCA);

4,4′-methylene-bis-(3-chloro-2,6-diethylaniline) (MCDEA); and isomers thereof;

wherein the stoichiometric ratio of the reactive hydrogen groups in the curative package to the unreacted isocyanate groups in the polyfunctional isocyanate is 0.95 to 1.05;

wherein the polishing layer exhibits a density of 0.75 to 1.0 g/cm 3 ; a Shore D hardness of 5 to 20; an elongation at break of 150 and 300%; and a cut rate of 30 to 60 μm/hr.

9. The multilayer chemical mechanical polishing pad stack of claim 8 , further comprising:

a subpad having a stack surface and a platen surface; and

a stack adhesive interposed between the bottom surface of the rigid layer and the stack surface of the subpad;

wherein the stack adhesive bonds the rigid layer to the subpad and wherein the stack side of the pressure sensitive platen adhesive layer is disposed on the platen surface of the subpad; and

optionally, a window incorporated into the multilayer chemical mechanical polishing pad stack.

10. The multilayer chemical mechanical polishing pad stack of claim 1 , wherein the polishing layer further comprises a plurality of hollow core polymeric materials.

11. A method of polishing a substrate, comprising:

providing a substrate selected from at least one of a magnetic substrate, an optical substrate and a semiconductor substrate;

providing a multilayer chemical mechanical polishing pad stack according to claim 1 ;

creating dynamic contact between a polishing surface of the polishing layer and the substrate to polish a surface of the substrate; and

conditioning of the polishing surface with an abrasive conditioner.

12. The multilayer chemical mechanical polishing pad stack of claim 1 , wherein the polishing layer is adapted for polishing a semiconductor wafer.

13. The multilayer chemical mechanical polishing pad stack of claim 10 , wherein the plurality of hollow core polymeric materials are incorporated into the polishing layer at 10 to 25 vol % porosity.

14. The multilayer chemical mechanical polishing pad stack of claim 10 , wherein the plurality of hollow core polymeric materials are uniformly distributed throughout the polishing layer.

15. The multilayer chemical mechanical polishing pad stack of claim 10 , wherein the plurality of hollow core polymeric materials have a weight average diameter of 10 to 50 μm.