Polishing pad and method of producing semiconductor device
A polishing pad enabling a highly precise optical endpoint sensing during the polishing process and thus having excellent polishing characteristics (such as surface uniformity and in-plane uniformity) is disclosed. A polishing pad enabling to obtain the polishing profile of a large area of a wafer is also disclosed. A polishing pad of a first invention comprises a light-transmitting region having a transmittance of not less than 50% over the wavelength range of 400 to 700 nm. A polishing pad of a second invention comprises a light-transmitting region having a thickness of 0.5 to 4 mm and a transmittance of not less than 80% over the wavelength range of 600 to 700 nm. A polishing pad of a third invention comprises a light-transmitting region arranged between the central portion and the peripheral portion of the polishing pad and having a length (D) in the diametrical direction which is three times or more longer than the length (L) in the circumferential direction.
1. An apparatus for chemical mechanical polishing in combination with a polishing pad and material to be polished, comprising said material to be polished and the polishing pad used in chemical mechanical polishing and having a polishing region and a light-transmitting region, said polishing pad having the following characteristics: i) light transmittance in the light-transmitting region throughout the wavelength range of 400 to 700 nm is 70% or more; and ii) a thickness of the light-transmitting region is 0.5 to 4 mm, and light transmittance in the light-transmitting region throughout the wavelength range of 500 to 700 nm is 90% or more;
wherein the light-transmitting region is arranged between a central portion and a peripheral portion of the polishing pad, and a length (D) of the light transmitting region in a diametrical direction is 3 times or more longer than a length (L) in a circumferential direction, wherein a length (D) in a diametrical direction is ¼ to ½ relative to the diameter of a material to be polished, and a scatter of the thickness of the light-transmitting region is 100 μm or less
wherein materials for forming the polishing region and the light-transmitting region are polyurethane resin, and the polyurethane resin as the material for forming the polishing region and the polyurethane resin as the material for forming the light-transmitting region are different materials but produced from the same kinds of organic isocyanate, polyol and chain extender, and
wherein the polyurethane resin as the material for forming the light-transmitting region does not contain aromatic polyamine and the material for forming the light transmitting region is non-foam,
wherein a material for forming the polishing region is fine-cell foam, and
wherein a rate of change of the light transmittance in the light-transmitting region in wavelengths of 400 to 700 nm represented by the following equation is 30% or less:
the rate of change (%)={(maximum transmittance in 400 to 700 nm−minimum transmittance in 400 to 700 nm)/maximum transmittance in 400 to 700 nm}×100.
2. The polishing pad according to any one of claim 1 , wherein a difference among respective light transmittances in the light-transmitting region in 500 to 700 nm is 5% or less.
3. The polishing pad according to claim 1 , wherein a shape of the light-transmitting region is rectangular.
4. The polishing pad according to claim 1 , which does not have an uneven structure for retaining and renewing an abrasive liquid on a surface of the light-transmitting region on a polishing side.
5. The polishing pad according to claim 1 , wherein a surface of the polishing region on a polishing side is provided with grooves.
6. The polishing pad according to claim 1 , wherein an average cell diameter of the fine-cell foam is 70 μm or less.
7. The polishing pad according to claim 1 , wherein a specific gravity of the fine-cell foam is 0.5 to 1.0 g/cm 3 .
8. The polishing pad according to claim 1 , wherein a hardness of the fine-cell foam is 45 to 65° in terms of Asker D hardness.
9. The polishing pad according to claim 1 , wherein a compressibility of the fine-cell foam is 0.5 to 5.0%.
10. An apparatus for chemical mechanical polishing in combination with a polishing pad and material to be polished, comprising said material to be polished and the polishing pad used in chemical mechanical polishing and having a polishing region and a light-transmitting region, said polishing pad having the following characteristics: i) light transmittance in the light-transmitting region throughout the wavelength range of 400 to 700 nm is 70% or more; and ii) a thickness of the light-transmitting region is 0.5 to 4 mm, and light transmittance in the light-transmitting region throughout the wavelength range of 500 to 700 nm is 90% or more;
wherein the light-transmitting region is arranged between a central portion and a peripheral portion of the polishing pad, and a length (D) of the light transmitting region in a diametrical direction is 3 times or more longer than a length (L) in a circumferential direction, wherein a length (D) in a diametrical direction is ¼ to ½ relative to the diameter of a material to be polished, and a material for forming the polishing region is fine-cell foam, wherein a compression recovery of the fine-cell foam is 50 to 100%
wherein materials for forming the polishing region and the light-transmitting region are polyurethane resin, and the polyurethane resin as the material for forming the polishing region and the polyurethane resin as the material for forming the light-transmitting region are different materials but produced from the same kinds of organic isocyanate, polyol and chain extender,
wherein the polyurethane resin as the material for forming the light-transmitting region does not contain aromatic polyamine and the material for forming the light transmitting region is non-foam, and
wherein a rate of change of the light transmittance in the light-transmitting region in wavelengths of 400 to 700 nm represented by the following equation is 30% or less:
the rate of change (%)={(maximum transmittance in 400 to 700 nm−minimum transmittance in 400 to 700 nm)/maximum transmittance in 400 to 700 nm}×100.
11. The polishing pad according to claim 1 , wherein a storage elastic modulus of the fine-cell foam at 40° C. at 1 Hz is 200 MPa or more.