Method for polishing silicon wafer, method for producing silicon wafer, apparatus for polishing disk-shaped workpiece, and silicon wafer

Abstract

The present invention is a method for polishing a silicon wafer, in which an oxide film is formed on a back surface side of the wafer, wherein the oxide film on a chamfered portion of the silicon wafer is removed, and the oxide film on a peripheral portion of the back surface of the wafer is polished over at least 2 mm from the outermost peripheral portion of the back surface of the wafer so that a thickness of the polished oxide film decreases from inside to outside of the wafer, a method for producing such a silicon wafer, and a silicon wafer. Thereby, there are provided a method for polishing a silicon wafer in which particles' attaching to a wafer surface after handling can be prevented, decrease of resistivity due to autodoping is not brought about, and moreover, productivity does not decrease; a method for producing such a silicon wafer; an apparatus for polishing a disk-shaped workpiece suitable for performing the methods; and a silicon wafer in which particles do not attach to a surface after handling even if an oxide film is formed on a back surface of the wafer and decrease of resistivity due to autodoping is not brought about.

1 . An apparatus for polishing a disk-shaped workpiece, comprising, at least, a rotating body having a surface inclined concentrically from outside to inside in a curved line or a straight line in which a polishing pad is attached to the surface; a driving means rotating and driving the rotating body; a workpiece holder holding the disk-shaped workpiece and pressing a peripheral portion of the workpiece against the polishing pad, wherein the polishing pad comprises a chamfered-portion polishing part in which a chamfered portion of the workpiece is polished and a back-surface polishing part in which a back surface of the workpiece is polished, and the polishing pad is attached to the rotating body so that an angle (α) which a tangent plane on a point of contact between the chamfered-portion polishing part and the chamfered portion of the workpiece forms with a rotation axis is in the range of 40° to 70°, and an angle (β) which a contact surface between the back-surface polishing part and the back surface of the workpiece forms with the rotation axis is in the range of 90° to 110°. 
     
     
         2 . The polishing apparatus according to  claim 1 , wherein the disk-shaped workpiece is a silicon wafer. 
     
     
         3 . The polishing apparatus according to  claim 1 , wherein the polishing pad removes an oxide film on a chamfered portion of the workpiece, and the polishing pad polishes the oxide film on the peripheral portion of the back surface of the workpiece over at least 2 mm from an outermost peripheral portion of the back surface of the workpiece so that a thickness of the polished oxide film decreases from inside to outside of the workpiece. 
     
     
         4 . The polishing apparatus according to  claim 2 , wherein the polishing pad removes an oxide film on a chamfered portion of the workpiece, and the polishing pad polishes the oxide film on the peripheral portion of the back surface of the workpiece over at least 2 mm from an outermost peripheral portion of the back surface of the workpiece so that a thickness of the polished oxide film decreases from inside to outside of the workpiece.