To start measurement by easily judging that a wafer is at a specified position and outputting a measurement command to a sensor controller.
An apparatus is equipped with a wafer rotating means 2, a rotation detecting means 3, a light projecting means 9 for projecting light to the edge part of the wafer, a CCD linear sensor 26 which is linearly arranged, and signal processing means 10 and 17 which detect the edge of the wafer and find at least one of an orientation flat position, a notch position, and a center position and further equipped with an up/down counter 21a which receives the signal of the rotation detecting means and converts it into rotation position information, a measurement angle setting register 21b which stores the rotation position information on rotation by an interval angle, and a comparator 21C which compares the set value of the measurement angle setting register with the count value of the up/down counter.
KATSUTA SHINICHI
ARINAGA YUJI
