Thin film thickness measuring method
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United States of America Patent
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Feb 6, 1990
Grant Date -
N/A
app pub date -
May 12, 1988
filing date -
May 12, 1988
priority date (Note) -
Expired
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Abstract
A method of measuring thin film thickness, especially on semiconductor substrates, in which the substrate is illuminated with ultraviolet light of a fixed wavelength corresponding to a persistent spectral line and the amount of light reflected from the substrate is detected and measured. The ultraviolet light preferably has a wavelength in the range from 240 nm to 300 nm, and the 253.6 nm spectral line of mercury is considered best. Comparing the measured amount of light from the substrate to a known amount of light detected from a standard calibration substrate with known reflectivity, the reflectivity of the test substrate is computed. The thickness of a thin film on the substrate is determined from the computed reflectivity using Fresnel's equation or a lookup table derived from the same.
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