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Method of controlling a chamber based upon predetermined concurrent behavior of selected plasma parameters as a function of selected chamber parameters

  • US 7,795,153 B2
  • Filed: 12/11/2006
  • Issued: 09/14/2010
  • Est. Priority Date: 05/16/2003
  • Status: Expired due to Fees
First Claim
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1. A method of processing a workpiece on workpiece support pedestal in a plasma reactor chamber in accordance with user-selected values of plural plasma parameters selected from a group comprising ion density, wafer voltage, etch rate, wafer current, by controlling chamber parameters selected from a group comprising source power, bias power, chamber pressure, magnet coil current, gas flow rates in respective zones and gas composition in respective zones, said method comprising:

  • for each one of said plural plasma parameters, fetching from a memory a contour of a constant plasma parameter numerical value corresponding to the user-selected value of said one plasma parameter, said contour being defined in a space of a dimension equal to the number of said selected chamber parameters, and determining an intersection of the corresponding contours, said intersection corresponding to respective target values of the selected chamber parameters;

    setting the values of said selected chamber parameters to the respective target values;

    subsequently controlling plasma bias power in a feedback control loop by sensing a difference between the user-selected value of wafer voltage and a concurrently measured value of wafer voltage and changing the plasma bias power to reduce said difference;

    subsequently controlling plasma source power in a feedback control loop by sensing a difference between the user-selected value of plasma ion density or etch rate and a measured value of plasma ion density or etch rate and changing the plasma source power to reduce said difference;

    obtaining said measured values of wafer voltage and plasma ion density by the steps of;

    (a.) sampling values of RF electrical parameters at an input end of a transmission line coupling RF bias power to an electrode within said wafer support pedestal, said electrode being connected to an output end of the transmission line;

    (b.) computing said measured value of wafer voltage from the sampled values of the RF electrical parameters; and

    (c.) computing said measured value of plasma ion density or etch rate from the sampled values of the RF electrical parameters.

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