Development of experimentally validated optical property models for silicon and related materials

A critical issue for rapid thermal processing (RTP), a single wafer integrated circuit manufacturing process, is how to reduce the temperature measurement uncertainty. Achieving high-accuracy temperature measurements using radiation thermometry requires knowledge of the optical properties of silicon and related materials. However, available optical property models lack consistency and are not fully validated by experiments at the wavelength and temperature ranges critical to radiation thermometry. To remedy this problem, researchers at the Georgia Institute and Technology and the National Institute of Standards and Technology (NIST) have collaborated to develop experimentally validated software tools for the calculation of radiative properties of silicon-related materials. In the present study, a survey of existing optical property models has identified the need for more thorough measurements of the radiative properties at the wavelengths between 0.8 μm and 1.0 μm. The radiative properties of multilayer structures was calculated using thin-film optics, and a spectrophotometer at NIST was used to measure the reflectance for selected samples in the wavelength region from 0.5 μm to 1 μm at room temperature. The measurement results agreed well with the predicted reflectance using the optical constants extrapolated from two existing expressions. This study will pave the way for the validation and development of optical property models of silicon and related materials at elevated temperatures.