Interferometer for in situ measurement of thin film thickness changes
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United States of America Patent
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-
Jun 15, 1993
Grant Date -
N/A
app pub date -
Dec 20, 1991
filing date -
Dec 20, 1991
priority date (Note) -
Expired
status (Latency Note)
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Abstract
An interferometer 10 for measuring the position of the process surface 21 of a substrate 20 includes a coherent light source 12 for providing a light beam 14 which is partially transmitted and partially reflected by a beam splitter 16. The reflected light beam 18 is reflected off of the process surface 21 and the transmitted light beam 30 is reflected off of a translator 32 which vibrates a predetermined distance at a predetermined frequency. The phase shift between the light beams 22, 31 reflected off of translator 32 and the process surface 21 is measured using a photodetector 24, which provides an output signal 26 to a feedback servo unit 28. The servo unit 28 provides an output signal 38 which controls the vibration of translator 32. The output signal 38 of servo unit 28 is also indicative of the position of the process surface 21.
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