Wafer and method of producing the same

• US 7,951,716 B2
• Filed: 02/16/2007
• Issued: 05/31/2011
• Est. Priority Date: 02/17/2006
• Status: Active Grant

• Current Assignee: Sumco Corporation
• Original Assignee: Sumco Corporation
• Inventors: Hujie, Kazuo, Ono, Isoroku, Morita, Etsurou
• Primary Examiner(s): OLSEN, ALLAN W
• Application Number:
  US11/707,312
• Publication Number:
  US 20070197035A1
• Time in Patent Office: 1,565 Days
• Field of Search: None
• US Class Current: 438/692
• CPC Class Codes: B24B 37/042 operating processes therefor
• CPC Class Codes: B24D 13/147 comprising assemblies of felted or spongy material; comprising pads surrounded by a flexible material

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.

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 μ

m 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;

wherein the polishing is carried out with a sheet-feed polishing machine;

wherein the polishing machine is provided with a controlling function which removes only a micro-projection existing on a rear surface of the wafer.

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 μ

m.

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.