Wafer and method of producing the same

Abstract

A wafer is produced at a step of polishing a predetermined face of a wafer to flatten the predetermined face while supplying a polishing liquid onto a bonded abrasive cloth, wherein the bonded abrasive cloth comprises a urethane bonding material consisting of a soft segment having a polyfunctional isocyanate and a hard segment having a polyfunctional polyol and having an expansion ratio of 1.1-4 times and silica having an average particle size of 0.2-10 μm and a hydroxy group, and has a given ratio of the hard segment occupied in the urethane bonding material, a given volume ratio of silica and a given Shore D hardness.

Description

BRIEF DESCRIPTION OF THE DRAWING

The invention will be described with reference to the accompanying drawings, wherein:

FIG. 1 is a schematic view of a main part of a sheet-feed polishing machine suitable for use in the production method of the invention illustrating a state just before polishing; and

FIG. 2 is a schematic view of a main part of a sheet-feed polishing machine suitable for use in the production method of the invention illustrating a polishing state.

Claims

1. A method of producing a wafer which comprises a step of polishing a predetermined face of a wafer to flatten the predetermined face while supplying a polishing liquid onto a bonded abrasive cloth, wherein the bonded abrasive cloth comprises a urethane bonding material consisting of a soft segment having a polyfunctional isocyanate and a hard segment having a polyfunctional polyol and having an expansion ratio of 1.1-4 times and silica having an average particle size of 0.2-10 μm and a hydroxy group, and a ratio of the hard segment occupied in the urethane bonding material is 40-55% as a molecular weight ratio, and a volume ratio of silica in the whole of the bonded abrasive cloth is within a range of 20-60%, and a Shore D hardness of the bonded abrasive cloth is 40-80.

2. A method of producing a wafer according to claim 1, wherein the predetermined face of the wafer is a rear face having a micro-projection(s) and the micro-projection is removed at a total polishing amount through a polishing.

3. A method of producing a wafer according to claim 2, wherein the total polishing amount is not more than 1 μm.

4. A method of producing a wafer according to claim 1, 2 or 3, wherein the wafer before the polishing step is a wafer after a heat treatment at a high temperature above 1100° C.

5. A method of producing a wafer according to any one of claims 1 to 3, wherein the wafer has a diameter of not less than 300 mm.

6. A method of producing a wafer according to any one of claims 1 to 3, wherein the polishing liquid is an alkali solution having a pH of 10-13.

7. A method of producing a wafer according to any one of claims 1 to 3, wherein the surface of the wafer is formed with a protection film prior to the polishing.

8. A method of producing a wafer according to claim 7, wherein the protection film is a thermal-oxidative film.

9. A method of producing a wafer according to claim 7, wherein the protection film is a tape seal used at the polishing step for the rear face of the wafer.

10. A method of producing a wafer according to any one of claims 1 to 3, wherein the polishing is carried out with a sheet-feed polishing machine.

11. A method of producing a wafer according to claim. 10, wherein the polishing machine is provided with a position controlling function.

12. A wafer heat-treated above 1100° C. and having a diameter of not less than 300 mm, wherein a micro-projection(s) having a height of not less than 10 nm is not existent on a rear surface of the wafer and a flatness (GBIR) of the wafer is not more than 0.35 μm.