Patent ID: 6951503

Claim:
A system of measuring and scanning a CMP polishing pad thickness comprising: a first sensor arm capable of being moved in a direction substantially parallel with and at a substantially constant top distance from a top surface of the CMP polishing pad; a first proximity sensor mounted on the first sensor arm, the first proximity sensor being oriented toward the top surface of the CMP polishing pad, the first proximity sensor being capable of measuring a first distance between the first proximity sensor and the top surface of the CMP polishing pad; a second sensor arm capable of being moved in a direction substantially parallel with and at a substantially constant bottom distance from a bottom surface of the CMP polishing pad; and a second proximity sensor mounted on the second sensor arm, the second proximity sensor being oriented toward the bottom surface of the CMP polishing pad, the second proximity sensor being capable of measuring a second distance between the second proximity sensor and the bottom surface of the CMP polishing pad, wherein the CMP polishing pad thickness is equal to a sum of a first difference and a second difference, the first difference equal to a difference between the top distance and the first distance, the second difference is equal to a difference between the bottom distance and the second distance.