Audio end point detector for chemical-mechanical polishing and method therefor
April 9, 2012. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 3841031 Polishing apparatus End point detection method for physical etching process End point detection Apparatus for polishing semiconductor wafers End point detection and control of laser induced dry chemical etching Semiconductor wafer surface grinding apparatus Dual detector system for determining endpoint of plasma etch process Method of detecting the endpoint of the etch of epitaxially grown silicon Method for detecting time for termination of surface layer removal processing InventorAssigneeApplicationNo. 865432 filed on 04/09/1992US Classes:451/10, And feeding of tool or work holder451/287Planar surface abradingExaminersPrimary: Rachuba, M.Attorney, Agent or FirmInternational ClassB24B 041/00AbstractAn apparatus for detecting a polishing endpoint during chemical-mechanical planarization/polishing of a wafer senses an acoustic wave generated by rubbing contact between a polish pad and a hard surface underlying a softer material being removed. The apparatus includes a transducer for converting the acoustic wave energy in the range of 30 to 100 Hertz into an audio signal. The audio signal is processed by a low pass cutoff filter to remove high frequency noise. The filtered audio signal is supplied to a phase lock loop to detect a predetermined audio frequency and, in response, provide a logic signal to an integrator. The integrator integrates the logic signal over time to eliminate transient noise spikes, and supplies a detection signal only upon receiving the logic signal for a predetermined period. The detection signal starts a counter to provide a predetermined overpolishing time prior to termination of polishing operations. | |
