WAFER ORIENTATION SENSOR FOR GaAs WAFERS

摘要

A wafer orienter includes a mechanism for rotating a wafer and a wafer orientation sensor. The wafer orientation sensor includes a light source for emitting light, a light sensor for sensing the light emitted by the light source as an edge of the wafer is rotated between the light source and the sensor and for producing a sensor signal representative of the sensed light, and an optical filter positioned between the light source and the light sensor. The optical filter has light-transmission characteristic wherein light in the pass band of the wafer is blocked. When the wafer orientation sensor is used for sensing gallium arsenide wafers, the optical filter is selected to block light at wavelengths greater than about 860 nanometers.