Patent ID: 11904432
Assignee: DISCO CORPORATION
Field: Machine tools (Mechanical engineering)
Classification: CPC B | IPC B

Claim 2:
3. A grinding apparatus comprising:
a chuck table having a holding surface to hold a wafer thereon, wherein an axis of rotation of the chuck table extends through a center of the holding surface;
a grinding unit that is mounted to a distal end of a spindle and that grinds the wafer by using a plurality of grindstones arranged in an annular fashion, the grindstones being rotated in such a manner as to pass above the center of the holding surface;
a spindle rotating mechanism configured to rotate the spindle;
a noncontact thickness measuring instrument configured to measure a thickness of the wafer held on the holding surface, in a noncontact manner; and
a rotation controlling section that causes the chuck table to rotate and that carries out rotation control by:
measuring the thickness of the wafer being ground with the noncontact thickness measuring instrument,
calculating a difference between a minimum value and a maximum value of cyclic variations in a thickness value of the wafer, wherein the variations are generated along a direction of rotation of the wafer, and
changing a rotational speed of the chuck table in a relative manner with respect to a rotational speed of the spindle based on the calculated difference between the minimum value and the maximum value of the cyclic variations in the thickness value of the wafer.