Method for manufacturing microporous CMP materials having controlled pore size
View Patent ↗A method of manufacturing a chemical-mechanical polishing (CMP) pad comprises the steps of (a) forming a layer of a polymer resin liquid solution (i.e., a polymer resin dissolved in a solvent); (b) inducing a phase separation in the layer of polymer solution to produce an interpenetrating polymeric network comprising a continuous polymer-rich phase interspersed with a continuous polymer-depleted phase in which the polymer-depleted phase constitutes about 20 to about 90 percent of the combined volume of the phases; (c) solidifying the continuous polymer-rich phase to form a porous polymer sheet; (d) removing at least a portion of the polymer-depleted phase from the porous polymer sheet; and (e) forming a CMP pad therefrom. The method provides for microporous CMP pads having a porosity and pore size that can be readily controlled by selecting the concentration polymer resin in the polymer solution, selecting the solvent based on the solubility parameters of the polymer in the solvent polarity of solvent, selecting the conditions for phase separation, and the like.
1. A method of manufacturing a chemical-mechanical polishing (CMP) pad comprising the steps of:
(a) forming a layer of a polymer resin liquid solution;
(b) inducing phase separation in the layer of polymer resin liquid solution to form an interconnected polymeric network comprising a continuous polymer-rich phase interspersed with a continuous polymer-depleted phase, the polymer-depleted phase comprising about 20 to about 90 percent of the combined volume of the separated phases, the phase separation being selected from the group consisting of a binodal decomposition, a spinodal decomposition, solvent-non-solvent induced phase separation, and a combination thereof;
(c) solidifying the polymer-rich phase to form a porous polymer sheet defining an open network of substantially interconnected pores and having at least a portion of the polymer-depleted phase dispersed within the pores, the polymer sheet having a porosity in the range of about 20 to about 90 percent by volume, the network of pores comiprising pores having diameters in the range of about 0.01 to about 10 microns;
(d) removing at least a portion of the polymer-depleted phase from the porous polymer sheet, wherein the step of removing the polymer-depleted phase is accomplished by a process selected from the group consisting of evaporation, solvent exchange, solvent stripping under vacuum, freeze drying and any combination thereof; and
(e) forming a CMP pad from the porous polymer sheet.
2. The method of claim 1 wherein the polymer resin is selected from the group consisting of a thermoplastic elastomer, a thermoplastic polyurethane, a thermoplastic polyolefin, a polycarbonate, a polyvinylalcohol, a nylon, an elastomeric rubber, an elastomeric polyethylene, a polytetrafluoroethylene, a polyethyleneteraphthalate, a polyimide, a polyaramide, a polyarylene, a polystyrene, a polymethylmethacrylate, a copolymers thereof, and a mixture thereof.
3. The method of claim 1 wherein the polymer resin comprises a thermoplastic polyurethane.
4. The method of claim 1 wherein the polymer resin liquid solution comprises a solvent selected from the group consisting of a polar aprotic solvent and a hydrogen bonding solvent.
5. The method of claim 1 wherein the solvent is selected from the group consisting of N-methylpyrrolidone, dimethylformamide, methyl ethyl ketone, tetrahydrofuran, dimethylacetamide, and a combination thereof.
6. The method of claim 1 wherein the step of inducing a phase separation is accomplished by cooling the layer of polymer resin liquid solution or by adding a non-solvent to the mixture.
7. The method of claim 1 wherein the step of forming a layer of polymer solution is accomplished by casting the polymer resin liquid solution onto a substrate.
8. The method of claim 1 wherein the step of forming a layer of polymer solution is accomplished by extruding a layer of the polymer resin liquid solution onto a substrate.
9. The method of claim 1 wherein the polymer resin liquid solution comprises about 1 to about 50 percent by weight of the polymer resin.
10. The method of claim 1 wherein the polymer resin liquid solution comprises about 5 to about 20 percent by weight of the polymer resin.