Method and apparatus for end point detection

Claim 1

A method of determining a time at which a radio frequency powered plasma etching process, etching a first material over a second different material, should be terminated when the first material is etched away exposing the second different material, wherein the method comprising the steps of: monitoring an optical emission intensity of said plasma etch process by a positive filter, a filter which generates a signal which increases in signal amplitude upon the detection of the first material being etched away, generating a first signal in response thereto, said first signal varying in intensity depending upon the etching process; simultaneously monitoring the optical emission intensity of said plasma etch process by a negative filter, a filter which generates a signal which decreases in signal amplitude upon the detection of the first material being etched away, generating a second signal in response thereto, said second signal varying in intensity depending upon the etching process; combining said first signal with said second signal to produce a combined signal; and detecting a change in said combined signal, wherein said change is indicative of said first material being etched away exposing said second different material.

Claim 2

A method of determining a time at which a radio frequency powered plasma etching process, etching a first material over a second different material, should be terminated when the first material is etched away exposing the second different material, wherein the method comprising the steps of: monitoring an optical emission intensity of said plasma etch process by a positive filter, a filter which generates a signal which increases in signal amplitude upon the detection of the first material being etched away, generating a first signal in response thereto, said first signal varying in intensity depending upon the etching process; simultaneously monitoring the optical emission intensity of said plasma etch process by a negative filter, a filter which generates a signal which decreases in signal amplitude upon the detection of the first material being etched away, generating a second signal in response thereto, said second signal varying in intensity depending upon the etching process; combining said first signal with said second signal to produce a combined signal; and detecting a change in said combined signal, wherein said change is indicative of said first material being etched away exposing said second different material.

Claim 8

An apparatus for determining a time at which a plasma etching process, etching a first material over a second different material, should be terminated when the first material is etched away exposing the second different material, said apparatus having means for generating said plasma, wherein the improvement comprising positive filter means for monitoring an optical emission intensity of said plasma etch process, and for generating a first signal in response thereto, said first signal varying in intensity depending upon the etching process and increasing in signal amplitude upon the detection of the first material being etched away; negative filter means for simultaneously monitoring the optical emission intensity of said plasma etch process, and for generating a second signal in response thereto, said second signal varying in intensity depending upon the etching process and decreasing in signal amplitude upon the detection of the first material being etched away; means for combining said first and second signals to produce a combined signal; and means for detecting a change in said combined signal, wherein said change is indicative of said first material being etched away exposing said second different material.

Claim 9

An apparatus for determining a time at which a plasma etching process, etching a first material over a second different material, should be terminated when the first material is etched away exposing the second different material, said apparatus having means for generating said plasma, wherein the improvement comprising positive filter means for monitoring an optical emission intensity of said plasma etch process, and for generating a first signal in response thereto, said first signal varying in intensity depending upon the etching process and increasing in signal amplitude upon the detection of the first material being etched away; negative filter means for simultaneously monitoring the optical emission intensity of said plasma etch process, and for generating a second signal in response thereto, said second signal varying in intensity depending upon the etching process and decreasing in signal amplitude upon the detection of the first material being etched away; means for combining said first and second signals to produce a combined signal; and means for detecting a change in said combined signal, wherein said change is indicative of said first material being etched away exposing said second different material.

Claim 12

The method of determining a time at which a radio frequency powered plasma etching apparatus, etching a first material over a second different material, should be terminated when the first material is etched away exposing the second different material wherein the radio frequency powered plasma etching apparatus has two settings for generating substantially the same amount of power output, wherein the method comprising the steps of: monitoring an optical emission intensity of said plasma etching process by a first filter generating a first output signal therefrom, said first output signal varying in intensity depending upon the etching process, wherein upon the exposure of the second material, said first output signal increases in signal amplitude and is a first detectable signal at said first setting of said apparatus, and said first output signal is a substantially undetectable signal at said second setting of said apparatus; simultaneously monitoring the optical emission intensity of said plasma etching process by a second filter generating a second output signal therefrom, said second output signal varying in intensity upon the etching process wherein upon the exposure of the second material, said second output signal decreases in signal amplitude and is a second detectable signal at said second setting of said apparatus, and said second output signal is a substantially undetectable signal at said first setting of said apparatus; combining said first and second output signals of said first and second filters; and detecting a change in said combined signal, wherein said change is indicative of said first material being etched away exposing said second different material.

Claim 13

The method of determining a time at which a radio frequency powered plasma etching apparatus, etching a first material over a second different material, should be terminated when the first material is etched away exposing the second different material wherein the radio frequency powered plasma etching apparatus has two settings for generating substantially the same amount of power output, wherein the method comprising the steps of: monitoring an optical emission intensity of said plasma etching process by a first filter generating a first output signal therefrom, said first output signal varying in intensity depending upon the etching process, wherein upon the exposure of the second material, said first output signal increases in signal amplitude and is a first detectable signal at said first setting of said apparatus, and said first output signal is a substantially undetectable signal at said second setting of said apparatus; simultaneously monitoring the optical emission intensity of said plasma etching process by a second filter generating a second output signal therefrom, said second output signal varying in intensity upon the etching process wherein upon the exposure of the second material, said second output signal decreases in signal amplitude and is a second detectable signal at said second setting of said apparatus, and said second output signal is a substantially undetectable signal at said first setting of said apparatus; combining said first and second output signals of said first and second filters; and detecting a change in said combined signal, wherein said change is indicative of said first material being etched away exposing said second different material.