Radiant energy – Invisible radiant energy responsive electric signalling – Ultraviolet light responsive means
Patent
1988-05-12
1990-02-06
Fields, Carolyn E.
Radiant energy
Invisible radiant energy responsive electric signalling
Ultraviolet light responsive means
356318, 356448, G01N 2155
Patent
active
048990558
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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Wesson et al., "Phase-Shift-Corrected Thickness Determination of Silicon Dioxide on Silicon by Ultraviolet Interference", Journal of Applied Physics, pp. 2455-2460, 1967.
Chiang et al., "Optical Evaluation of Polycrystalline Silicone Surface Roughness", Journal of the Electrochemical Society, pp. 2267-2268, 1979.
Duffy et al., "Measurement of the Near-Surface Crystallinity of Silicon on Sapphire by UV Reflectance", Journal of Crystal Growth, pp. 10-18, 1982.
Harbeke et al., "Rapid Characterization of Polysilicon Films by Means of a UV Reflectometer", RCA Review, vol. 44, pp. 19-29, Mar. 1983.
Fields Carolyn E.
Schneck Thomas
Tencor Instruments
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