Numerical investigation of heat transfer in ultrafast laser processing of silicon material

Abstract

An investigation of ultrafast laser-material interaction between a femtosecond pulsed laser beam and a semiconductor material is considered in this work. A two-temperature model (TTM), conventionally used in laser processing of metals, was extended for the simulation of the semiconductor thermal response. TTM is known for its capability for predicting the laser fluences required to achieve non-thermal ablation. We use silicon as the model material for the laser-material interaction. A single laser pulse irradiated to the surface of the silicon was simulated to obtain the temporal and spatial evolution of the carrier density and temperature as well as the lattice temperature. The results showed that a non-thermal ablation, based from carrier density criterion, is achieved at specific laser fluence. The numerical investigation was continued for multi-pulse femtosecond laser interaction. A heat accumulation is investigated for different laser repetition rates. This model for multi-pulse laser-material interaction is a promising tool to determine the optimal laser parameters in laser material processing.