Transient Temperature During Pulsed Excimer Laser Heating of Thin Polysilicon Films Obtained by Optical Reflectivity Measurement

The transient reflectivity of a continuous wave (CW) HeNe laser was measured during the pulsed excimer laser heating of thin polysilicon films at the nanosecond time scale. Polysilicon films with thicknesses from 0.1 to 0.4 μm were deposited by Low-Pressure Chemical Vapor Deposition (LPCVD) on thermally oxidized crystalline silicon wafers. The complex refractive index of these films at the HeNe laser wavelength (λprobe = 0.6328 μm) was measured in the temperature range from 300 K to approximately 1400 K by combined ellipsometric and normal incidence reflectivity measurements. Numerical heat transfer and optical reflectivity analysis based on the measured optical properties of polysilicon films were conducted. The calculated reflectivity histories were compared with the experimental results to reveal the transient temperature field.