Wafer reader including a mirror assembly for reading wafer scribes without displacing wafers

摘要

A wafer reader for reading scribes from the surface of semiconductor wafers uses a mirror assembly with a series of stationary mirrors spaced apart so that the mirrors can be inserted between wafers in a cassette. The mirror assembly enables a reader unit to read each scribe without displacing the wafer that it is reading or the adjacent wafers. The reader unit can include a single camera that moves relative to a stationary cassette assembly for holding a cassette or a moving cassette the moves past a fixed reading position of a single, stationary camera. Alternatively, the reader unit can include more than one stationary camera, each capable of reading more than one wafer in a cassette. The reader can use either bright or dark field lighting. In either case, each mirror in the mirror assembly re-directs light depicting a wafer scribe from the surface of an adjacent wafer to the camera assembly.