Local heating method by a Nd:YAG laser beam for the measurements of the optical properties of Si wafers

Abstract

The local heating method by a Nd:YAG laser beam was applied to Si wafers to evaluate thermal variations of their optical properties.
Firstly, the optical properties such as transmittance, reflectance and absorptance for the Nd:YAG laser beam (the wavelength, 1.06 μm), and their variations with temperature ranging from the room temperature to near the melting point (1685°K) were measured. From the results, the variations of the absorption coefficients were derived and correlated with the calculated thermal variation of the energy gap.
Secondly, the numerical simulations for the temperature distribution, and the temperature gradient distribution on the locally heated specimen by Nd:YAG laser beam were carried out by using Bessel function. The locally generated thermal stress is also discussed.