Characterization of residual stress in a SiC drilling hole using ns pulse laser machining by Raman spectroscopy

This study integrates Raman spectroscopy and COMSOL simulations to investigate residual stress induced by nanosecond pulsed laser drilling in 4H-SiC wafers. The Heat Transfer in Solids module with an axis-symmetrical model was employed in the FEM analysis, combined with the formed geometry. Experimentally, a 1064 nm ytterbium fiber laser was used to drill through-holes with 50 pulses, achieving a depth of 350 μ m . Raman mapping near the hole edge revealed a nearly symmetric stress distribution, with peak values of 30–45 MPa on either side. The simulation, conducted with 45 pulses, predicted a hole depth of 345 μm with a 1.43 % error and a maximum stress of 33 MPa, based on the biaxial stress model, showing good agreement with the experimental data. Despite discrepancies in peak stress magnitudes, the overall spatial trends were consistent. In addition, based on a six-stress field extracted from simulation, the predicted Raman shift is approximately −0.14 cm −1 , which is compared to the experimental data of −0.16 cm −1 , resulting in a relative error of 12.5 %. Additionally, experimental measurements showed that the heat-affected zone (HAZ) extended to approximately 600 μm when a 60 μm-diameter hole was drilled using a focused spot diameter of approximately 15 μm. The simulation results also predicted an HAZ width of roughly 600 μm, showing excellent agreement with the experimental observations. It is concluded that a simple heat-conduction model using an axisymmetric domain accurately predicts the residual stress and the HAZ around the hole, both of which match the experimental results. This agreement is further strengthened by validation using Raman-shift projections from the full stress field, which provides a direct and internally consistent basis for comparison.