Patent ID: 6293845
Filing Date: 2001-09-25
Classification: B24B

Abstract:
A method for detecting a planarization process step endpoint of a semiconductor wafer planarization operation, said method comprising:monitoring a motor current signal for at least one motor responsible for a component of relative movement between said semiconductor wafer and a polishing pad;performing a Fourier transform analysis of the monitored motor current signal to identify at least one motor current signal frequency component of said signal identifying a periodic mechanical oscillation arising from operational effects independent from planarization process step completion indicators;filtering said at least one identified frequency component to suppress said periodic oscillations from said motor current signal and generating a filtered motor current signal in which motor current signal variations indicative of said planarization process step completion are preserved and more readily detectable relative to motor current at times other than said planarization process step endpoint; anddetecting said planarization process step completion as a change in the filtered motor current signal;said fourier transform analysis and filtering at said identified frequency component ensuring that an undesirable oscillation in the monitored motor current are minimized to thereby provide better reliability and higher precision of said planarization process step completion detection.