Substrate temperature measurement and control by emissivity compensated pyrometry during metalorganic vapor phase epitaxy of III-V device structures in large scale rotating disc reactors

The growth process for many III-V semiconductor devices is quite temperature sensitive. The temperature window for some of the more challenging device structures can be as narrow as 2-3/spl deg/C, depending upon how tight the final device specifications are. Clearly, measurement and control of the growth temperature in a MOVPE production environment is critical to maintaining high yields from the growth process. We have solved this problem by using a pyrometric technique known as emissivity compensated pyrometry. This in-situ measurement technique requires the combined functionality of a conventional pyrometer and a reflectometer. The reflectance of the substrate is measured at the same wavelength that the pyrometer measures the thermal radiance. By using the equation /spl epsi/=1-R the spectral directional emissivity of the substrate surface can be calculated from the measured spectral directional reflectivity. This allows the measured thermal emission to be constantly corrected for the changing emissivity of the growth surface. In this way, the accurate temperature of the substrate can be measured at any time during growth.