Femtosecond laser modification of silicon carbide substrates and its influence on CMP process

Abstract

Silicon carbide (SiC) is one of the most promising third-generation semiconductor materials owing to its superior comprehensive performances. However, high-efficient polishing of the hard-to-process SiC substrate remains a challenge due to its high hardness and high chemical stability. In this paper, the SiC substrate was irradiated by femtosecond laser to enhance the subsequent chemical mechanical polishing (CMP) efficiency. The effects of different laser processing parameters such as laser fluence, focus position, scanning velocity and scanning interval on the surface morphology of SiC were discussed. The influences of the surrounding conditions on the morphology of laser-processed surfaces were also studied. Results show that the Si–O compound was formed on the laser-irradiated SiC surfaces, which is beneficial for the subsequent CMP process due to their lower hardness. Furthermore, the uniform periodic ripple structures formed on the laser-irradiated SiC surface also help to improve the surface flatness. Furthermore, fewer surface defects and lower surface roughness can be achieved in an oxygen atmosphere, which was due to the oxygen participating in the photochemical reaction.