METHOD OF FEEDBACK CONTROL OF ESC VOLTAGE USING WAFER VOLTAGE MEASUREMENT AT THE BIAS SUPPLY OUTPUT
First Claim
Patent Images
1. In a plasma reactor having an electrostatic chuck (ESC) supporting a wafer to be processed, a method of processing the wafer while controlling an ESC clamping voltage, comprising:
- applying RF bias power to said ESC from a bias power source at an input to said ESC and applying a D.C. voltage at said input to said ESC from a D.C. voltage source;
measuring voltage and current near said input to produce a measured voltage and a measured current;
providing a wafer voltage signal as a sum of said measured voltage and said measured current multiplied by first and second coefficients respectively, said wafer voltage signal representing the voltage on a wafer supported on said ESC; and
computing a wafer clamping voltage as a difference between a D.C. component of said wafer voltage signal and said D.C. voltage from said D.C. voltage source, and controlling said D.C. voltage to regulate said wafer clamping voltage.
0 Assignments
0 Petitions
Accused Products
Abstract
In a plasma reactor having an electrostatic chuck, wafer voltage is determined from RF measurements at the bias input using previously determined constants based upon transmission line properties of the bias input, and this wafer voltage is used to accurately control the DC wafer clamping voltage.
-
Citations
16 Claims
-
1. In a plasma reactor having an electrostatic chuck (ESC) supporting a wafer to be processed, a method of processing the wafer while controlling an ESC clamping voltage, comprising:
-
applying RF bias power to said ESC from a bias power source at an input to said ESC and applying a D.C. voltage at said input to said ESC from a D.C. voltage source;
measuring voltage and current near said input to produce a measured voltage and a measured current;
providing a wafer voltage signal as a sum of said measured voltage and said measured current multiplied by first and second coefficients respectively, said wafer voltage signal representing the voltage on a wafer supported on said ESC; and
computing a wafer clamping voltage as a difference between a D.C. component of said wafer voltage signal and said D.C. voltage from said D.C. voltage source, and controlling said D.C. voltage to regulate said wafer clamping voltage. - View Dependent Claims (2, 3, 4, 5, 6)
-
-
7. In a plasma reactor having a wafer voltage controller and an electrostatic chuck (ESC) for clamping a wafer to be processed in the reactor, a method for determining a wafer voltage for use by the controller, comprising:
-
applying plasma RF bias power comprising first and second frequency components, f(1), f(2), respectively, to an input of said ESC;
providing measurement signals representing first and second frequency components of a measured voltage and first and second frequency components of a measured current at said input of said ESC;
providing first and second frequency components of a wafer voltage signal as, respectively, a first sum of the first frequency components of said measured voltage and measured current multiplied by first and second coefficients respectively, and a second sum of the second frequency components of said measured voltage and measured current multiplied by third and fourth coefficients, respectively; and
computing a D.C. wafer voltage by combining D.C. components of said first and second frequency components of said wafer voltage with a correction factor comprising a product of said D.C. components of said first and second components of said wafer voltage raised to a selected power and multiplied by a selected coefficient. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16)
-
Specification