Method of controlling a chamber based upon predetermined concurrent behavior of selected plasma parameters as a function of selected chamber parameters
First Claim
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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Abstract
The invention involves a method of processing a workpiece on workpiece support pedestal in a plasma reactor chamber in accordance with user-selected values of plural (i.e., N) plasma parameters by controlling plural chamber parameters. The plasma parameters may be selected from of a group including ion density, wafer voltage, etch rate, wafer current and possibly other plasma parameters. The chamber parameters may be selected from a group including source power, bias power, chamber pressure, magnet coil current of different coils, gas flow rate in different gas injection zones, gas species composition in different gas injection zones, and possibly other chamber parameters. The method begins with a first step carried out for each one of the selected plasma parameters. This first step consists of fetching from a memory a relevant surface of constant value corresponding to the user-selected value of the one plasma parameter, the surface being defined in a N-dimensional space of which each of the N chamber parameters is a dimension. This step further includes determining an intersection of these relevant surfaces, the intersection corresponding to a target value of each of the N chamber parameter. The method further includes setting each of the N chamber parameters to the corresponding target value.
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Citations
12 Claims
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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:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of processing a workpiece on a 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 and wafer current, by controlling chamber parameters selected from a group comprising source power, bias power, chamber pressure, magnet coil current and gas flow rate, the number of said plural plasma parameters being less than the number of said chamber parameters, said method comprising:
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for each one of said plural plasma parameters, fetching a surface of a constant plasma parameter numerical value corresponding to the user-selected value of said one plasma parameter, and determining an intersection of the corresponding surfaces which defines a line in a space whose dimension is equal to the number of said selected chamber parameters; varying said selected chamber parameters along said line; subsequently controlling plasma bias power by sensing a difference between the user-selected value of wafer voltage and a measured value of wafer voltage and changing the plasma bias power to reduce said difference; and subsequently controlling plasma source power 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 or etch rate 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. - View Dependent Claims (11, 12)
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Specification