| 摘要 |
PURPOSE:To enable a mirror-like surface to be nicely formed in a thin layer by decreasing a cut-in speed when rotational speed of grindstone is increased due to an increase in motor current, that is, a grinding resistance is increased, and increasing the same in the reverse case. CONSTITUTION:When GaAs semiconductor wafer 1 is fixed to a chuck table 2 on an index table 3 so as to grind its back face, the grinding process is carried out for making cut-in feed by means of a servo-motor 10 via a cut-in screw 9 while turning a cup type diamond wheel 6. In this case, a grindstone cut-in speed control circuit Z finds out a grinding resistance R from the current valve I of a motor 8 detected by a spindle motor current analyzing circuit X and the rotational speed OMEGA of the motor 8 detected by a spindle rotational speed analyzing circuit Y, and a servo-motor 10 is controlled in such a way that if this resistance R is larger than a preset value, cut-in speed phi is decreased and if it is smaller than the preset value, said speed is increased. Thus, the wafer can be formed in a thin layer without generating any crack and a clean mirror-like surface can be finished. |
