Patent ID: 11967506
Assignee: DISCO CORPORATION
Field: Machine tools (Mechanical engineering)
Classification: CPC H  B | IPC B  H

Claim 0:
1. A grinding apparatus for grinding a wafer, comprising:
at least four chuck tables for holding respective wafers on holding surfaces thereof;
a first grinding mechanism for grinding the wafer held on the holding surface of one of the chuck tables by keeping lower surfaces of first grindstones arranged in an annular array on a first grinding wheel in contact with a radial area of the wafer;
a second grinding mechanism for grinding the wafer held on the holding surface of one of the chuck tables by keeping lower surfaces of second grindstones arranged in an annular array on a second grinding wheel in contact with a radial area of the wafer;
a third grinding mechanism for grinding the wafer held on the holding surface of one of the chuck tables by keeping lower surfaces of third grindstones arranged in an annular array on a third grinding wheel in contact with a radial area of the wafer;
a first grinding feed mechanism for grinding-feeding the first grinding mechanism in a grinding feed direction perpendicular to the holding surface of one of the chuck tables;
a second grinding feed mechanism for grinding-feeding the second grinding mechanism in a grinding feed direction perpendicular to the holding surface of one of the chuck tables;
a third grinding feed mechanism for grinding-feeding the third grinding mechanism in a grinding feed direction perpendicular to the holding surface of one of the chuck tables;
a turntable with the chuck tables mounted thereon, the turntable being rotatable about a central axis of the turntable for positioning the chuck tables respectively with respect to the first grindstones, the second grindstones, and the third grindstones; and
a control unit,
wherein:
the first grinding mechanism and the second grinding mechanism are positioned with respect to the chuck tables such that a second ground mark produced on the wafer by the second grindstones when the wafer is ground by the second grindstones extends across a first ground mark produced on the wafer by the first grindstones when the wafer is ground by the first grindstones, wherein the first ground mark is developed radially inwardly on the wafer by the control unit by rotating the first grinding wheel in a clockwise direction while simultaneously rotating an associated one of the chuck tables in the clockwise direction and wherein the second ground mark is developed radially inwardly on the wafer by the control unit by rotating the second grinding wheel in a counter-clockwise direction while simultaneously rotating an associated one of the chuck tables in the counter-clockwise direction, and
the second grinding mechanism and the third grinding mechanism are positioned with respect to the chuck tables such that a third ground mark produced on the wafer by the third grindstones when the wafer is ground by the third grindstones extends across the second ground mark produced on the wafer by the second grindstones, wherein the third ground mark is developed radially inwardly on the wafer by the control unit by rotating the third grinding wheel in a clockwise direction while simultaneously rotating an associated one of the chuck tables in the clockwise direction.