METHOD FOR POLISHING SILICON WAFER AND POLISHING LIQUID THEREFOR

• US 20130032573A1
• Filed: 03/23/2011
• Published: 02/07/2013
• Est. Priority Date: 04/30/2010
• Status: Active Grant

• Current Assignee: Sumco Corporation
• Original Assignee: Sumco Corporation
• Inventors: Ogata, Shinichi, Tanimoto, Ryuichi, Mikuriya, Shunsuke, Yamasaki, Ichiro
• Granted Patent: US 8,932,952 B2
• Time in Patent Office: Days
• US Class Current: 216/53
• CPC Class Codes: B24B 37/044 characterised by the composition of the lapping agent
• CPC Class Codes: B24B 37/08 for double side lapping
• CPC Class Codes: B24B 37/245 Pads with fixed abrasives
• CPC Class Codes: B24B 37/28 for double side lapping of plane surfaces
• CPC Class Codes: H01L 21/02024 Mirror polishing

Abstract

Disclosed is a method for polishing a silicon wafer, wherein a surface to be polished of a silicon wafer is rough polished, while supplying a polishing liquid, which is obtained by adding a water-soluble polymer to an aqueous alkaline solution that contains no free abrasive grains, to a polishing cloth. Consequently, the surface to be polished can be polished at high polishing rate and the flatness of the edge portion including roll-off and roll-up can be controlled.

Claims

1. A method for polishing silicon wafers comprising the steps of:

rough polishing at least the surface serving as a surface to be polished between a surface and a rear surface of the silicon wafer so as to relatively rotate a silicon wafer and an abrasive cloth while supplying a polishing liquid in which a water-soluble polymer is added to an alkaline aqueous solution with no free abrasive grains, to the hard abrasive cloth; and

applying final polishing on at least the rough polished surface of the silicon wafer.

3. The method for polishing silicon wafers according to claim 1, wherein the water-soluble polymer is one type or several types from among non-ionic system polymers and monomers, or one type or several types from among anionic system polymers and monomers.

4. The method for polishing silicon wafers according to claim 3, wherein the water-soluble polymer is hydroxyethyl cellulose.

5. The method for polishing silicon wafers according to claim 4, wherein the concentration of the hydroxyethyl cellulose in the polishing liquid is 0.1 ppm to 1000 ppm.

6. The method for polishing silicon wafers according to claim 1, wherein

the alkaline aqueous solution is adjusted to pH8 to pH13, and

the alkaline aqueous solution is the alkaline aqueous solution to which any of basic ammonium salt, basic potassic salt, and basic sodium salt is added as an alkaline agent, or an alkaline carbonate aqueous solution, or an alkaline aqueous solution to which an amine is added.

7. The method for polishing silicon wafers according to claim 1, wherein the abrasive cloth is composed of a nonwoven cloth made of polyester, or is made of polyurethane.

8. The method for polishing silicon wafers according to claim 1, wherein the rough polishing simultaneously polishes the surface and the rear surface of the silicon wafer with a double-side polishing device which includes a carrier plate in which a silicon wafer is housed, and an upper surface plate in which the abrasive cloth is pasted on a lower surface and a lower surface plate in which the abrasive cloth is pasted on a top surface, which holds the carrier plate from above and below therebetween.

9. The method for polishing silicon wafers according to claim 8, wherein polishing is carried out such that a thickness of the silicon wafer after the rough polishing is made thicker than a thickness of the carrier plate.

2. A method for polishing silicon wafers comprising the steps of:

rough polishing at least the surface serving as a surface to be polished between a surface and a rear surface of the silicon wafer so as to relatively rotate a silicon wafer and an abrasive cloth; and

applying final polishing on at least the rough polished surface of the silicon wafer after the rough polishing, the method wherein

the rough polishing is split into a first-step polishing which is carried out while supplying a first-step polishing liquid in which a water-soluble polymer is added to an alkaline aqueous solution with no free abrasive grains to the abrasive cloth, and a second-step polishing which is carried out while supplying a second-step polishing liquid in which a water-soluble polymer is added to an alkaline aqueous solution with no free abrasive grains to the abrasive cloth after the first-step polishing, and

concentration of the water-soluble polymer in the second-step polishing liquid is made higher than the concentration of the water-soluble polymer in the first-step polishing liquid.

10. A polishing liquid which is used at the time of rough polishing at least the surface serving as a surface to be polished between a surface and a rear surface of a silicon wafer, wherein

an alkaline aqueous solution with no free abrasive grains serves as a base compound, and a water-soluble polymer is added to the alkaline aqueous solution.

11. The polishing liquid according to claim 10, wherein

the alkaline aqueous solution is adjusted to pH8 to pH13,

the alkaline aqueous solution is the alkaline aqueous solution to which any of basic ammonium salt, basic potassic salt, and basic sodium salt is added as an alkaline agent, or an alkaline carbonate aqueous solution, or an alkaline aqueous solution to which an amine is added, and

the water-soluble polymer is one type or several types from among non-ionic system polymers and monomers, or one type or several types from among anionic system polymers and monomers.

12. The polishing liquid according to claim 10, wherein the water-soluble polymer is hydroxyethyl cellulose.

13. The polishing liquid according to claim 12, wherein the concentration of the hydroxyethyl cellulose in the alkaline aqueous solution is adjusted to be within a range of concentration from 0.1 ppm to 1000 ppm.