| 摘要 |
Robot arm (16) end effectors (10, 110, 210) of this invention rapidly and cleanly transfer semiconductor wafers (12) between a wafer cassette (14) and a processing station. The end effectors include fiber optic light transmission sensors (90, 102, 202, 214) for determining various wafer surface, edge, thickness, tilt, and location parameters. The sensors provide robot arm extension and elevation positioning data supporting methods of rapidly and accurately placing and retrieving a wafer from among a stack of closely spaced wafers stored in the wafer cassette. The methods effectively prevent accidental contact between the end effector and the wafers while effecting clean, secure gripping of the wafer.
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