Method of determining plasma ion density, wafer voltage, etch rate and wafer current from applied bias voltage and current
First Claim
1. In a plasma reactor chamber having a wafer support pedestal for supporting a wafer inside the reactor, said pedestal having an insulated electrode beneath the wafer and a transmission line coupling said electrode to a bias impedance match element for an RF bias generator, a method of determining plasma ion density, wafer voltage, etch rate and wafer current in said chamber, said method comprising:
- sensing RF parameters corresponding to an input impedance, an input current and an input voltage at the input of said impedance match element to said transmission line;
computing a junction admittance of a junction between said transmission line and the electrode within the wafer pedestal from said input impedance, input current and input voltage and from parameters of the transmission line;
providing shunt electrical quantities of a shunt capacitance between the electrode and a ground plane;
providing load electrical quantities of a load capacitance between the electrode and a wafer on the pedestal;
computing at least one of said etch rate, plasma ion density and wafer voltage and wafer current from said junction admittance, said shunt electrical quantities, said load electrical quantities and a frequency of RF bias power applied to said electrode.
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Abstract
Plasma parameters such as plasma ion density, wafer voltage, etch rate and wafer current in the chamber are determined from external measurements on the applied RF bias electrical parameters such as voltage and current. The method includes sensing RF parameters corresponding to an input impedance, an input current and an input voltage at the input of the impedance match element to a transmission line coupled between the bias generator and the wafer pedestal. The method continues by computing a junction admittance of a junction between the transmission line and the electrode within the wafer pedestal from the input impedance, input current and input voltage and from parameters of the transmission line. The method further includes providing shunt electrical quantities of a shunt capacitance between the electrode and a ground plane, and providing load electrical quantities of a load capacitance between the electrode and a wafer on the pedestal. The method further includes computing at least one of the plasma parameters from the junction admittance, the shunt electrical quantities, the load electrical quantities and a frequency of RF bias power applied to the electrode.
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Citations
9 Claims
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1. In a plasma reactor chamber having a wafer support pedestal for supporting a wafer inside the reactor, said pedestal having an insulated electrode beneath the wafer and a transmission line coupling said electrode to a bias impedance match element for an RF bias generator, a method of determining plasma ion density, wafer voltage, etch rate and wafer current in said chamber, said method comprising:
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sensing RF parameters corresponding to an input impedance, an input current and an input voltage at the input of said impedance match element to said transmission line;
computing a junction admittance of a junction between said transmission line and the electrode within the wafer pedestal from said input impedance, input current and input voltage and from parameters of the transmission line;
providing shunt electrical quantities of a shunt capacitance between the electrode and a ground plane;
providing load electrical quantities of a load capacitance between the electrode and a wafer on the pedestal;
computing at least one of said etch rate, plasma ion density and wafer voltage and wafer current from said junction admittance, said shunt electrical quantities, said load electrical quantities and a frequency of RF bias power applied to said electrode. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification