Patent ID: 6562187
Filing Date: 2003-05-13
Classification: H01J,H01L

Abstract:
An endpointing arrangement for ascertaining an end of an etch process while etching through a target layer on a substrate in a plasma processing system, comprising:an electrostatic chuck having a first pole and a second pole; a first DC power supply coupled to said first pole and said second pole for supplying chucking voltages to said first pole and said second 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; a second current monitoring circuit coupled between said second pole and said first DC power supply for monitoring a second current supplied to said second pole, said second current monitoring circuit outputting a second signal indicative of said second current; a differential amplifier arrangement coupled to said first current monitoring circuit and said second current monitoring circuit, said differential amplifier arrangement receives said first signal and said second signal as input and outputs a control signal; a variable DC power supply coupled to said differential amplifier arrangement for receiving said control signal, said variable DC power supply being configured to output a compensation voltage for biasing said first DC power supply responsive to said control signal; and an endpoint monitoring circuit coupled to said variable DC power supply, said endpoint monitoring circuit receives as an input said compensation voltage and includes circuitry for analyzing said compensation voltage for a pattern characteristic of said end of said etch process, said endpoint monitoring circuit further including circuitry for outputting an endpoint signal indicative of said end of said etch process upon ascertaining said pattern in said compensation voltage.