Method for determining the temperature of semiconductor substrates from bandgap spectra
First Claim
1. An optical method for measuring the temperature of a semiconductor substrate material in a process chamber comprising:
- (a) emitting radiation from a light source thereby causing broad spectrum radiation to be incident upon the substrate;
(b) using a wavelength selective detection system to measure a band edge spectrum of the substrate;
(c) analyzing the band edge spectrum to determine a position of a knee of the spectrum;
(d) analyzing the band edge spectrum to determine a width of the knee of the spectrum;
(e) determining a corrected position of the knee of the spectrum using the width of the knee of the spectrum, and;
(f) computing the temperature of the substrate from the corrected position of the knee of the spectrum.
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Abstract
An optical method for measuring the temperature of a substrate material with a temperature dependent band edge. In this method both the position and the width of the knee of the band edge spectrum of the substrate are used to determine temperature. The width of the knee is used to correct for the spurious shifts in the position of the knee caused by: (i) thin film interference in a deposited layer on the substrate; (ii) anisotropic scattering at the back of the substrate; (iii) the spectral variation in the absorptance of deposited layers that absorb in the vicinity of the band edge of the substrate; and (iv) the spectral dependence in the optical response of the wavelength selective detection system used to obtain the band edge spectrum of the substrate. The adjusted position of the knee is used to calculate the substrate temperature from a predetermined calibration curve. This algorithm is suitable for real-time applications as the information needed to correct the knee position is obtained from the spectrum itself. Using a model for the temperature dependent shape of the absorption edge in GaAs and InP, the effect of substrate thickness and the optical geometry of the method used to determine the band edge spectrum, are incorporated into the calibration curve.
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Citations
19 Claims
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1. An optical method for measuring the temperature of a semiconductor substrate material in a process chamber comprising:
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(a) emitting radiation from a light source thereby causing broad spectrum radiation to be incident upon the substrate; (b) using a wavelength selective detection system to measure a band edge spectrum of the substrate; (c) analyzing the band edge spectrum to determine a position of a knee of the spectrum; (d) analyzing the band edge spectrum to determine a width of the knee of the spectrum; (e) determining a corrected position of the knee of the spectrum using the width of the knee of the spectrum, and; (f) computing the temperature of the substrate from the corrected position of the knee of the spectrum. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. An optical method for measuring the temperature of a semiconductor substrate material in a process chamber comprising:
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(a) emitting radiation from a light source thereby causing broad spectrum radiation to be incident upon the substrate; (b) using a wavelength selective detection system to measure a band edge spectrum of the substrate; (c) analyzing the band edge spectrum to determine the position of a knee of the spectrum; (d) determining a corrected knee position by adding a term to the determined knee position that corrects for the effects of changes in the positions of the light source or the wavelength selective detection system relative to their positions in the determination of a calibration curve, the term being proportional to the logarithm of an optical path length in the substrate, and; (e) computing the temperature of the substrate by comparing the corrected knee position, with the position of a knee in a calibration curve from a reference substrate.
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Specification