Optical apparatus and method for measuring temperature of a substrate material with a temperature dependent band gap
First Claim
1. An optical method for measuring the temperature of a substrate material in a process chamber comprising:
- (a) emitting radiation from an external light source to thereby cause broad spectrum radiation to be incident upon the front surface of the substrate;
(b) placing a diffuse scattering element at the back of the substrate in the optical path of the light source to reflect the light rays from the external light source in a non-specular path through the substrate;
(c) locating a wavelength selective detection system in a non-specular position with respect to rays from the light source that are reflected from the front surface of the substrate;
(d) analyzing the non-specularly reflected light from the substrate to determine the knee in the spectrum of the non-specularly reflected light; and
(e) computing the temperature of the substrate from the knee in the spectrum.
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Abstract
An optical method for measuring the temperature of a substrate material with a temperature dependent bandgap. The substrate is illuminated with a broad spectrum lamp and the bandgap is determined from the spectrum of the diffusely scattered light. The spectrum of the light from the lamp is sufficiently broad that it covers the spectral range above and below the bandgap of the substrate. Wavelengths corresponding to photon energies less than the bandgap of the substrate are transmitted through the substrate and are reflected from the back surface of the substrate as well as from the front surface while the wavelengths corresponding to photon energies larger than the bandgap are reflected only from the front surface. If the front surface is polished the front surface reflection will be specular while if the back surface is rough the reflection from the back surface will be non-specular. The back surface reflection is detected with a detector in a non-specular location. From the wavelength of the onset of the non-specular reflection the bandgap can be determined which gives the temperature. The temperature is determined from the knee in the diffuse reflectance spectrum near the bandgap.
64 Citations
9 Claims
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1. An optical method for measuring the temperature of a substrate material in a process chamber comprising:
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(a) emitting radiation from an external light source to thereby cause broad spectrum radiation to be incident upon the front surface of the substrate; (b) placing a diffuse scattering element at the back of the substrate in the optical path of the light source to reflect the light rays from the external light source in a non-specular path through the substrate; (c) locating a wavelength selective detection system in a non-specular position with respect to rays from the light source that are reflected from the front surface of the substrate; (d) analyzing the non-specularly reflected light from the substrate to determine the knee in the spectrum of the non-specularly reflected light; and (e) computing the temperature of the substrate from the knee in the spectrum. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification