Device and method for optimally detecting a surface condition of wafers

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;
• and
• a filter controller for controlling a selection of the filters based on said reflectivity;
• and
• a 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;
• and
• a plurality of air cylinders, coupled to the solenoid valves, to move said at least one filter.