Patent ID: 6285199
Filing Date: 2001-09-04
Classification: G01R

Abstract:
A device for detecting surface conditions of wafers, the device comprising:a light generating unit for impinging light on a wafer to generate reflected light;a combining unit, including a plurality of filters having different light attenuation factors, for receiving the reflected light and outputting an attenuated amount of the reflected light;a detection unit for receiving the attenuated amount of the reflected light from the combining unit and processing the received light to detect a surface condition of the wafer;a reflection rate detector for detecting a reflectivity of the wafer; anda filter controller for controlling a selection of the filters based on said reflectivity; anda filter driving unit including:a solenoid valve driving unit operating under control of the filter controller;a plurality of solenoid valves operating under control of the solenoid valve driving unit; anda plurality of air cylinders, coupled to the solenoid valves, to move said at least one filter.