Controlled-viscosity CMP casting method
View Patent ↗The invention provides a method of manufacturing a polishing pad suitable for planarizing at least one of semiconductor, optical and magnetic substrates. The method obtains a liquid polyurethane material formed from an isocyanate-terminated molecule and a curative agent. The liquid polyurethane material contains 4.2 to 7.5 weight percent fluid-filled polymeric microspheres in the isocyanate-terminated molecule. The fluid-filled polymeric microspheres are a blend of preexpanded and unexpanded fluid-filled polymeric microspheres. The liquid polyurethane material contains a blend of preexpanded and unexpanded fluid-filled polymeric microspheres having a relative viscosity μ μ 0 of 1.1 to 7. Then the liquid polyurethane material solidifies into a polyurethane matrix that contains preexpanded and expanded fluid-filled polymeric microsphere for forming the polishing pad.
1. A method of manufacturing a polishing pad suitable for planarizing at least one of semiconductor, optical and magnetic substrates, the method comprising the following:
obtaining a liquid polyurethane material formed from an isocyanate-terminated molecule and a curative agent, the liquid polyurethane material having a
T gel temperature and containing 4.2 to 7.5 weight percent fluid-filled polymeric microspheres in the isocyanate-terminated molecule, the fluid-filled polymeric microspheres are a blend of preexpanded and unexpanded fluid-filled polymeric microspheres, the preexpanded and unexpanded fluid-filled polymeric microspheres each having a T start temperature where diameter of the preexpanded and unexpanded fluid-filled polymeric microspheres increases at temperatures equal to or above the T start temperature, with the T start temperature of the unexpanded fluid-filled polymeric microspheres being at least 5° C. less than the T gel temperature of the liquid polyurethane material;
casting the liquid polyurethane material containing the blend of preexpanded and unexpanded fluid-filled polymeric microspheres, the liquid polyurethane material containing the blend of preexpanded and unexpanded fluid-filled polymeric microspheres having a relative viscosity
μ
μ
0
of 1.1 to 7, wherein
μ
μ
0
=
1
+
2.5
ϕ
+
10.05
ϕ
2
+
0.00273
ⅇ
16.6
ϕ
where μ is the viscosity of the filled system, μ 0 the viscosity of the unfilled material,
μ
μ
0
the relative viscosity, and Φ the volume fraction of the filler;
heating and curing the liquid polyurethane material and the blend of prexpanded and unexpanded fluid-filled polymeric microspheres to a temperature of at least T start of the unexpanded fluid-filled polymeric microspheres to increase the diameter of the unexpanded fluid-filled polymeric microspheres and to form a blend of preexpanded and expanded fluid-filled polymeric microspheres in the liquid polyurethane material and then solidify the liquid polyurethane material into a polyurethane matrix containing the preexpanded and expanded fluid-filled polymeric microspheres; and
forming the polishing pad from the polyurethane matrix containing the preexpanded and expanded fluid-filled polymeric microspheres.
2. The method of claim 1 including the additional step of mixing the blend of preexpanded and unexpanded fluid-filled polymeric microspheres in the liquid polyurethane material before casting.
3. The method of claim 1 wherein the casting is into a cake mold to form a polyurethane cake structure; and including the additional steps of removing the polyurethane cake structure from the mold and skiving the cake structure into multiple polyurethane sheets; and the forming the polishing pads is from the polyurethane sheets.
4. The method of claim 1 wherein the casting includes pouring the liquid polyurethane material and the blend of preexpanded and expanded fluid-filled polymeric microspheres around a transparent block and the forming the polishing pad includes a transparent window in the polishing pad.
5. A method of manufacturing a polishing pad suitable for planarizing at least one of semiconductor, optical and magnetic substrates, the method comprising the following:
obtaining a liquid polyurethane material formed from an isocyanate-terminated molecule and a curative agent, the liquid polyurethane material having a
T gel temperature and containing 4.2 to 7.5 weight percent fluid-filled polymeric microspheres in the isocyanate-terminated molecule, the fluid-filled polymeric microspheres are a blend of preexpanded and unexpanded fluid-filled polymeric microspheres filled with isobutane, isopentane or a mixture of isobutane and isopentane, the preexpanded and unexpanded fluid-filled polymeric microspheres each having a T start temperature where diameter of the preexpanded and unexpanded fluid-filled polymeric microspheres increases at temperatures equal to or above the T start temperature, with the T start temperature of the unexpanded fluid-filled polymeric microspheres being at least 5° C. less than the T gel temperature of the liquid polyurethane material;
casting the liquid polyurethane material containing the blend of preexpanded and unexpanded fluid-filled polymeric microspheres, the liquid polyurethane material containing the blend of preexpanded and unexpanded fluid-filled polymeric microspheres having a relative viscosity
μ
μ
0
of 1.1 to 7, wherein
μ
μ
0
=
1
+
2.5
ϕ
+
10.05
ϕ
2
+
0.00273
ⅇ
16.6
ϕ
where μ is the viscosity of the filled system, μ 0 the viscosity of the unfilled material,
μ
μ
0
the relative viscosity, and Φ the volume fraction of the filler;
heating and curing the liquid polyurethane material and the blend of prexpanded and unexpanded fluid-filled polymeric microspheres to a temperature of at least T start of the unexpanded fluid-filled polymeric microspheres to increase the diameter of the unexpanded fluid-filled polymeric microspheres and to form a blend of preexpanded and expanded fluid-filled polymeric microspheres in the liquid polyurethane material and then solidify the liquid polyurethane material into a polyurethane matrix containing the preexpanded and expanded fluid-filled polymeric microspheres; and
forming the polishing pad from the polyurethane matrix containing the preexpanded and expanded fluid-filled polymeric microspheres.
6. The method of claim 5 including the additional step of mixing the blend of preexpanded and unexpanded fluid-filled polymeric microspheres in the liquid polyurethane material before casting.
7. The method of claim 5 wherein the casting is into a cake mold to form a polyurethane cake structure; and including the additional steps of removing the polyurethane cake structure from the mold and skiving the cake structure into multiple polyurethane sheets; and the forming the polishing pads is from the polyurethane sheets.
8. The method of claim 5 wherein the casting includes pouring the liquid polyurethane material and the blend of preexpanded and expanded fluid-filled polymeric microspheres around a transparent block and the forming the polishing pad includes a transparent window in the polishing pad.