Grinding pad and method of producing the same
The invention provides a polishing pad by which optical materials such as lenses, reflecting mirrors etc., or materials requiring a high degree of surface planarity, as in the polishing of silicone wafers, glass substrates or aluminum substrates for hard disks, or general metal polishing, can be flattened with stability and high polishing efficiency. The invention also provides a polishing pad for semiconductor wafers, which is superior in planarizing characteristic, is free from scratches and can be produced at low cost. There is provided a polishing pad which is free from dechucking error so that neither damage to wafers nor decrease in operating efficiency occurs. There is provided a polishing pad which is satisfactory in planarity, within wafer uniformity, and polishing rate and produces less change in polishing rate. There is provided a polishing pad which can make planarity improvement and scratch decrease compatible.
1. A semiconductor wafer polishing pad whose polishing layer is resin foam of closed-cell type, wherein the number of closed cells in the polishing layer is 200 to 600 per mm 2 , and the average diameter of the closed cells is 30 to 60 μm, wherein
a resin constituting the resin foam consists of a polyurethane resin produced by mixing a first component containing an isocyanate group-containing compound with a second component containing an active hydrogen group-containing compound followed by hardening the mixture by heating, said mixture containing a curing agent and a silicone-based surfactant,
the resin foam has a hardness of 45 or more and less than 65 as measured using a D-type rubber hardness meter, and
the closed cells solely contain gas selected from the group consisting of nitrogen, oxygen, a rare gas, dry air, and a mixed gas of the foregoing,
wherein the polyurethane resin foam contains the silicone-based surfactant in amount of 0.05 to 4.5 wt % based on the total amount of the first and second component.
2. The polishing pad according to claim 1 , wherein the polyurethane resin are produced by mixing an organic polyisocyanate as the first component, a polyol as the second component, the silicone-based surfactant and the curing agent, wherein the major ingredient of the curing agent is 4,4′-methylenebis(o-chloroaniline), and the polyol comprises polytetramethylene glycol having a number-average molecular weight of 500 to 1600 and a molecular-weight distribution (weight-average molecular weight/number-average molecular weight) of less than 1.9.
3. The polishing pad according to claim 1 , wherein the density of the polyurethane resin foam is 0.67 to 0.90 g/cm 3 .
4. The polishing pad according to claim 1 , wherein the silicone-based surfactant is a polyalkylsiloxane/polyether copolymer.
5. The polishing pad according to claim 1 , wherein the resin foam contains the silicone-based surfactant represented by a chemical formula selected from the following chemical formulas 1 to 6:
wherein R f is C 2 H 4 C y F 2y+1 ,
wherein m and n are an integer, and the substituent X in the chemical formulas 1 to 4 is selected from substituent groups represented by a chemical formula selected from the following chemical formulas 1 to 6:
(Formula 9)
—C 3 H 6 O(C 2 H 4 O) a (C 3 H 6 O) b R
(Formula 10)
—C 3 H 6 O(CH 2 CH(OH)CH 2 O) a H
(Formula 11)
—C 3 H 6 N + (CH 3 ) 2 CH 2 COO −
(Formula 12)
—C 3 H 6 O(C 2 H 4 O) a SO 3 Na
(Formula 13)
—C 3 H 6 N + (CH 3 ) 3 .Cl −
wherein a and b are an integer.
6. The polishing pad according to claim 5 , wherein the density of the polyurethane resin foam is 0.67 to 0.90 g/cm 3 .
7. The polishing pad according to claim 5 , wherein the polyurethane resin foam contains 0.05 to 5 wt % silicone-based surfactant.
8. The polishing pad according to claim 7 , wherein the silicone-based surfactant is a polyalkylsiloxane/polyether copolymer.