| 摘要 |
An identification mark constituted of irregularities is formed on the surface of a wafer, which is sealed with a resin layer and a dicing tape may be adhered to the backside. Multiple infrared units irradiate infrared rays towards the surface of the wafer from the backside thereof, wherein they transmit through the wafer and are then reflected at the interface between the resin layer and the surface of the wafer, thus producing reflected rays. An image pickup device picks up an image of the interface including the identification mark based on reflected rays. Optical axes of the infrared units extend to cross the surface of the wafer in different directions; hence, the image pickup device receives only a part of reflected rays, which are reflected at the interface in a prescribed direction. A polarizer can be arranged in proximity to the infrared unit or the image pickup device.
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