Method of determining wafer voltage in a plasma reactor from applied bias voltage and current and a pair of constants
First Claim
1. In a plasma reactor chamber containing a wafer support pedestal having an electrode and an RF bias power generator coupled through an impedance match circuit to the input end of a transmission line whose output end is coupled to the electrode, a method of measuring plasma ion energy or wafer voltage of a wafer on the pedestal during plasma processing of the wafer, comprising:
- prior to plasma processing of the wafer, determining first and second constants characteristic of the plasma reactor chamber and storing said first and second constants in a memory;
during plasma processing of the wafer performing the following steps;
a. sampling an RF input current and an RF input voltage at said impedance match circuit;
b. multiplying said RF input voltage by said first constant to produce a first product;
c. multiplying said RF input current by said second constant to produce a second product; and
d. computing a sum of said first and second products.
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Accused Products
Abstract
The voltage of a wafer on the pedestal of an RF plasma reactor is instantly determined from the applied bias current and the applied bias voltage sampled during plasma processing of the wafer using a pair constants. Prior to plasma processing of the wafer, a determination is made of first and second constants based upon electrical characteristics of a transmission line through which RF power is coupled to the pedestal. During plasma processing of the wafer, the wafer voltage is determined by performing the steps of sampling an RF input current and an RF input voltage at the impedance match circuit; multiplying the RF input voltage by the first constant to produce a first product; multiplying the RF input current by the second constant to produce a second product; and computing a sum of the first and second products.
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Citations
6 Claims
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1. In a plasma reactor chamber containing a wafer support pedestal having an electrode and an RF bias power generator coupled through an impedance match circuit to the input end of a transmission line whose output end is coupled to the electrode, a method of measuring plasma ion energy or wafer voltage of a wafer on the pedestal during plasma processing of the wafer, comprising:
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prior to plasma processing of the wafer, determining first and second constants characteristic of the plasma reactor chamber and storing said first and second constants in a memory;
during plasma processing of the wafer performing the following steps;
a. sampling an RF input current and an RF input voltage at said impedance match circuit;
b. multiplying said RF input voltage by said first constant to produce a first product;
c. multiplying said RF input current by said second constant to produce a second product; and
d. computing a sum of said first and second products. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification