3-D Simulator of Laser Crystallization for Polycrystalline-Silicon Thin-Film Transistors
A 3-D simulator of laser crystallization for polycrystalline-silicon thin-film transistors has been developed. Random nucleation, crystal growth velocity, latent heat emission, and partial crystallization are modeled, and a 2-D algorithm is extended to a 3-D algorithm. The <formula formulatype="inline"><tex Notation="TeX">$\mu$</tex></formula>-Czochralski technique is analyzed using the 3-D simulator, and it is found that the grain size becomes large when the initial temperature is high after the laser irradiation.
Sample temperature profile during the excimer laser annealing of silicon nanoparticles
Abstract Based on the heat diffusion equation we describe the temperature profile of a silicon nanoparticle thin film on silicon during excimer laser annealing using COMSOL Multiphysics. For this purpose system specific material parameters are determined such as the silicon nanoparticle melting point at 1683 K, the surface reflectivity at 248 nm of 20% and the nanoparticle thermal conductivity between 0.3 and 1.2 W/m K. To validate our model, the simulation results are compared to experimental data obtained by Raman spectroscopy, SEM microscopy and electrochemical capacitance–voltage measurements (ECV). The experimental data are in good agreement with our theoretical findings and support the validity of the model.
Diffusion of arsenic in polycrystalline silicon
The diffusion of arsenic in polycrystalline silicon films has been studied over the temperature range 750–950 °C and for grain sizes 210–510 nm. Rutherford backscattering spectrometry was used to measure the concentration profiles of arsenic, initially introduced into the polysilicon by ion implantation, after various annealing steps. The concentration profiles were found to be determined by a combination of two factors—the low diffusivity in the bulk of the rains and the much higher diffusivity in the grain boundaries. The diffusivity of arsenic in the grain boundaries was independent of concentration, with an activation energy of 3.9 eV, very close to that of the low‐concentration arsenic diffusivity in single‐crystal silicon. However, the value of the diffusivity was 8.6×104 exp(−3.9/kT)cm2/s, four orders of magnitude higher than the single‐crystal value. The diffusivity in the interior of the grains was the same as that in single‐crystal silicon.