Patent ID: 11890716
Assignee: EBARA CORPORATION
Field: Machine tools (Mechanical engineering)
Classification: CPC B | IPC B

Claim 0:
1. A polishing unit comprising:
a rotatable polishing table to which a polishing pad for polishing a substrate is attached;
a top ring configured to hold the substrate to press the substrate against the polishing pad;
a slip-out detector comprising:
a light source configured to emit a light to a detection area on the polishing pad; and
a light detector configured to detect the light reflected from the detection area;

the slip-out detector configured to detect a slip out of the substrate from the top ring based on the light reflected from the detection area; and
an elimination mechanism configured to eliminate a polishing liquid flowing into the detection area, the elimination mechanism located at an upstream side of the light detector in a direction of rotation of the polishing table,
wherein the slip-out detector is configured to detect the slip out of the substrate from the top ring based on a difference between a reference color and a color of light reflected from the detection area of the polishing pad during a polishing process,
wherein the polishing unit is configured to count a cumulative number of polishing processes of the substrate,
wherein the polishing unit is configured to reset the reference color of the slip-out detector and automatically register the reference color based on the light reflected from the detection area when the counted cumulative number of polishing processes exceeds a threshold value, and
wherein the slip-out detector is configured to detect the slip out of the substrate from the top ring based on a difference between the registered reference color and the color of light reflected from the detection area of the polishing pad during the polishing process.