A High-speed Tunable Multi-wavelength Thermal Imager

An innovative imaging technique is proposed for surface/wafer temperature measurement in a chemical vapor deposition (CVD) reactor. Limitations in measuring absolute, as well as relative temperature in a CVD reactor, limit the ability to utilize intelligent processing of material, including feedback or forward control of the CVD process. Comparison of the ratios of spectral radiance at several wavelengths to the theoretical ratios of intensity derived from Planck's radiation law allows the evaluation of absolute temperature indepdent of the absolute photo flux. Current multiple-wavelength pyrometry, event though able to overcome the wavelength dependency of emissivity, is handicapped by its inability to measure radiance at multiple wavelengths simultaneously. The proposed technique uses an acousto-optic tunable filter (AOTF) to rapidly obtain multiple spectral radiance information. Under Phase I, the proposed temperature measuring system will be developed and optimized to improve the scanning rate, bandpass and signal-to-noise ratio. Under Phase II, the developed temperature measuring system will be applied in conjunction with an intelligent process control technique to a material process, such as the growth of InP or GaAs in a CVD reactor. ANTICIPATED BENEFITS: The system (thermal sensor and process control) developed would have a significant commercial impact on increasing quality control of electronic, photonic, aerospace and high strength materials.