Patent ID: 6741913
Filing Date: 2004-05-25
Classification: B24B

Abstract:
A method for reducing noise in an endpoint detection system in a chemical-mechanical polishing (CMP) apparatus, the apparatus including a polishing pad and a workpiece carrier connected to a shaft, the carrier rotating in accordance with rotation of the shaft and oscillating with respect to the polishing pad, the endpoint detection being performed according to measurements associated with friction between the polishing pad and the workpiece, the method comprising the steps of:computing, in a first computing step, a plurality of values at a predetermined time interval, each of the values being an average of a plurality of said measurements performed in a time period approximately equal to a rotation period of the carrier; forming an array of successive values computed in said first computing step, the array being characterized as a moving array including the most recently computed value, the array having a size such that a product of the moving array size and the time interval is approximately an integral multiple of an oscillation period of the carrier; and computing, in a second computing step, an average of the values in the array to obtain an array average at each successive time interval.