Method of shaping holding surface of chuck table

Abstract

A second relative speed where a spindle and a center of a holding surface are brought together in a grinding step is established such that the spindle and the outer circumferential edge of a surrounding region of the holding surface start being brought together other along a first direction and the spindle's rotational shaft and the holding surface's center start being brought together along a second direction simultaneously and that the spindle and the outer circumferential edge of the surrounding region finish being brought together along the first direction and the spindle's rotational shaft and the holding surface's center finish being brought together along the second direction simultaneously. Specifically, the second relative speed is established in view of parameters that are established as desired and the worn-off amount of the grindstones that is grasped prior to or during the grinding step (i.e., a change in thickness of the grindstones).

What is claimed is: 
     
         1 . A method of shaping a holding surface of a chuck table of a grinding apparatus that includes the chuck table that is rotatable and has a circular holding surface and a spindle including a distal end portion on which a grinding wheel that has a plurality of grindstones disposed in an annular array is mounted, in which, when the spindle is rotated, the plurality of grindstones follow a track having an outside diameter smaller than a radius of the holding surface, and the method shapes the holding surface of the chuck table by grinding the holding surface of the chuck table such that a surrounding region of the holding surface that is positioned radially outwardly of a first concentric circle region of the holding surface that is radially spaced from a center of the holding surface by a distance that corresponds to the outside diameter of the track is slanted so as to be progressively deeper toward the first concentric circle region and that the center and the first concentric circle region are of a predetermined depth from an outer circumferential edge of the surrounding region and a second concentric circle region positioned radially between the center and the first concentric circle region is deeper than the center and the first concentric circle region, the method comprising:
 an adjusting step of adjusting a tilt of at least one of the spindle or the chuck table such that the plurality of grindstones will come into initial contact with a third concentric circle region of the holding surface that is radially positioned between the first concentric circle region and the second concentric circle region when the spindle and the holding surface are moved toward each other along a first direction;   after the adjusting step, a contacting step of, while the spindle and the chuck table are being rotated, bringing the spindle and the outer circumferential edge of the surrounding region toward each other along the first direction until the plurality of grindstones contact the outer circumferential edge of the surrounding region; and   after the contacting step, a grinding step of, while the spindle and the chuck table are being rotated and the spindle and the outer circumferential edge of the surrounding region are being brought toward each other at a first relative speed along the first direction, bringing a rotational shaft of the spindle and the center of the holding surface toward each other at a second relative speed along a second direction perpendicular to the first direction until the plurality of grindstones contact the center of the holding surface,   wherein, in the grinding step, the spindle and the outer circumferential edge of the surrounding region are brought toward each other along the first direction by a first traveled distance represented by a sum of the predetermined depth and a worn-off amount of the plurality of grindstones that are worn by grinding the chuck table to the predetermined depth,   in the grinding step, the rotational shaft of the spindle and the center of the holding surface are brought toward each other along the second direction by a second traveled distance equal to a width of the surrounding region along the second direction,   the first relative speed is a constant speed established as desired, and   the second relative speed is a constant or variable speed established in view of the predetermined depth, the worn-off amount, the second traveled distance, and the first relative speed such that the spindle and the outer circumferential edge of the surrounding region start being brought toward each other along the first direction and the rotational shaft of the spindle and the center of the holding surface start being brought toward each other along the second direction simultaneously and that the spindle and the outer circumferential edge of the surrounding region finish being brought toward each other along the first direction and the rotational shaft of the spindle and the center of the holding surface finish being brought toward each other along the second direction simultaneously.   
     
     
         2 . The method of shaping a holding surface of a chuck table according to  claim 1 , wherein
 the worn-off amount has been grasped prior to the contacting step, and   the second relative speed is a speed that is obtained by dividing the second traveled distance by a time obtained by dividing the first traveled distance by the first relative speed.   
     
     
         3 . The method of shaping a holding surface of a chuck table according to  claim 1 , wherein
 the surrounding region includes a first portion and a second portion positioned radially inwardly of the first portion and slanted with a larger gradient than the first portion,   the grinding step includes
 a preliminary grinding step of forming the first portion in the surrounding region by bringing the spindle and the outer circumferential edge of the surrounding region toward each other along the first direction by a third traveled distance and bringing the rotational shaft of the spindle and the center of the holding surface toward each other along the second direction by a fourth traveled distance while the spindle and the chuck table are being rotated, 
 after the preliminary grinding step, a measuring step of measuring a depth of an inner circumferential edge of the first portion from the outer circumferential edge of the surrounding region, and 
 a main grinding step of forming the second portion in the surrounding region by bringing the spindle and the outer circumferential edge of the surrounding region toward each other along the first direction by a fifth traveled distance and bringing the rotational shaft of the spindle and the center of the holding surface toward each other along the second direction by a sixth traveled distance while the spindle and the chuck table are being rotated, 
   the second relative speed in the preliminary grinding step is a speed that is obtained by dividing the second traveled distance by a time obtained by dividing the predetermined depth by the first relative speed,   the third traveled distance represents a distance established as desired in a range smaller than the predetermined depth,   the fourth traveled distance represents a distance that is obtained by multiplying the second relative speed in the preliminary grinding step by a time obtained by dividing the third traveled distance by the first relative speed,   the worn-off amount represents a distance that is obtained by multiplying the predetermined depth by a value that is obtained by dividing a distance obtained by subtracting the depth of the inner circumferential edge of the first portion measured in the measuring step from the third traveled distance by the depth of the inner circumferential edge of the first portion measured in the measuring step,   the fifth traveled distance represents a distance that is obtained by adding a distance obtained by subtracting the third traveled distance from the predetermined depth and the worn-off amount to each other,   the sixth traveled distance represents a distance that is obtained by subtracting the fourth traveled distance from the second traveled distance, and   the second relative speed in the main grinding step is a speed that is obtained by dividing the sixth traveled distance by a time obtained by dividing the fifth traveled distance by the first relative speed.