Patent ID: 6228278
Filing Date: 2001-05-08
Classification: H01J,H01L

Abstract:
A method for ascertaining an end of an etch process while etching through a target layer on a substrate in a plasma processing system, said plasma processing system including an electrostatic chuck having a first pole, a first DC power supply coupled to said first pole for supplying a chucking voltage to said first pole, a first current monitoring circuit coupled between said first pole and said first DC power supply for monitoring a first current supplied to said first pole, said first current monitoring circuit outputting a first signal indicative of said first current, and a variable DC power supply configured to output a compensation voltage for biasing said first DC power supply responsive to said first signal, thereby causing said chucking voltage to vary responsive to said compensation voltage, said method comprising:coupling an endpoint monitoring circuit to said variable DC power supply, said endpoint monitoring circuit having an endpoint monitoring input and an endpoint monitoring output;receiving at said endpoint monitoring input said compensation voltage;analyzing, using said endpoint monitoring circuit, said compensation voltage for a pattern characteristic of said end of said etch process; andoutputting at said endpoint monitoring output an endpoint signal indicative of said end of said etch process upon ascertaining said pattern in said compensation voltage.