Method of grinding wafer

Abstract

After a first recess whose bottom is of a shape represented by a side surface of an inverted cone is formed in a reverse side of a wafer and before a second recess whose bottom is of a circular shape is formed in the reverse side of the wafer, a chuck table and a spindle are spaced from each other to separate a plurality of grindstones and the reverse side of the wafer from each other, and then a tilt of at least one of the chuck table or the spindle is adjusted to change an angle formed between a rotational axis about which the chuck table is rotatable and a rotational axis about which the spindle is rotatable.

What is claimed is: 
     
         1 . A method of grinding a wafer on a grinding apparatus including a chuck table that has a holding surface and that is rotatable about a first rotational axis passing through a center of the holding surface, a spindle rotatable about a second rotational axis, and a grinding wheel mounted on a distal end of the spindle and supporting thereon an annular array of grindstones disposed at spaced intervals, the wafer having a face side with a plurality of devices formed thereon and a radius longer than an outside diameter of a track to be followed by a grinding surface of each of the grindstones when the spindle is rotated, the method comprising:
 a holding step of holding the wafer on the holding surface of the chuck table with a reverse side of the wafer that is opposite the face side thereof being exposed;   after the holding step, a first grinding step of grinding the reverse side of the wafer by keeping a center of the wafer and the track superposed on each other in a predetermined direction while rotating the chuck table and the spindle respectively about the first rotational axis and the second rotational axis, and moving the chuck table and the spindle closer to each other in the predetermined direction to bring the grindstones into abrasive contact with the reverse side of the wafer;   after the first grinding step, a separating step of spacing the chuck table and the spindle from each other in a direction opposite the predetermined direction to separate the grindstones and the reverse side of the wafer from each other;   after the separating step, an adjusting step of adjusting a tilt of at least one of the chuck table or the spindle to change an angle formed between the first rotational axis and the second rotational axis; and   after the adjusting step, a second grinding step of grinding the reverse side of the wafer by keeping the center of the wafer and the track superposed on each other in the predetermined direction while rotating the chuck table and the spindle respectively about the first rotational axis and the second rotational axis, and moving the chuck table and the spindle closer to each other in the predetermined direction to bring the grindstones into abrasive contact with the reverse side of the wafer,   wherein the first grinding step includes forming a first recess whose bottom is of a shape represented by a side surface of an inverted cone in the reverse side of the wafer, and   the second grinding step includes forming a second recess whose bottom is of a circular shape in the reverse side of the wafer.   
     
     
         2 . The method of grinding a wafer according to  claim 1 , further comprising:
 after the separating step and before the second grinding step, a cleaning step of cleaning the bottom of the first recess.   
     
     
         3 . The method of grinding a wafer according to  claim 2 , further comprising:
 after the separating step and before the second grinding step, a position adjusting step of moving the chuck table and the spindle toward or away from each other in a direction perpendicular to the predetermined direction.   
     
     
         4 . The method of grinding a wafer according to  claim 1 , further comprising:
 after the separating step and before the second grinding step, a position adjusting step of moving the chuck table and the spindle toward or away from each other in a direction perpendicular to the predetermined direction.