| CPC H01L 21/6833 (2013.01) [B08B 3/04 (2013.01); B08B 5/04 (2013.01); B08B 7/00 (2013.01); C23C 14/505 (2013.01); H01L 21/67011 (2013.01)] | 20 Claims |

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1. A method comprising:
moving an optical inspection instrument under a bottom surface of a chuck;
emitting, by a first portion of the optical inspection instrument, a radiation toward a bottom surface of the chuck, wherein the chuck is configured for fixing a semiconductor workpiece on the bottom surface, and the optical inspection instrument faces the bottom surface;
receiving, by a second portion of the optical inspection instrument, a reflection of the radiation reflected from the chuck to obtain a continuous line of intensities corresponding to locations on the chuck;
analyzing the reflection of the radiation based on the continuous line of the intensities corresponding to the locations on the chuck;
in response to that the continuous line of the intensities corresponding to the locations on the chuck has a valley, determining a particle is present on the bottom surface of the chuck;
after determining the particle is presented, moving the optical inspection instrument away from the bottom surface of the chuck;
after moving the optical inspection instrument away from the bottom surface of the chuck, moving a cleaning tool to a position under the bottom surface of the chuck; and
removing the particle by using the cleaning tool comprising an exhaust duct.
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