The Polishing Effect of SiC Substrates in Femtosecond Laser Irradiation Assisted Chemical Mechanical Polishing (CMP)

Silicon carbide (SiC) is conceived to be one of the next-generation semiconductor materials owning to its outstanding properties and numerous potential applications. However, polishing the hard-to-process SiC substrate remains as a challenge due to its high Mohs hardness and high chemical stability. New technique should be developed aiming at high polishing efficiency and high surface accuracy for chemical mechanical polishing (CMP). This paper presents an emerging approach by employing femtosecond (fs) laser as a pre-process for CMP process. By irradiating the C-faces in transverse and cross-scanning irradiation modes sequentially, both the irradiated and the non-irradiated substrates were simultaneously polished in CMP process with normal colloidal silica slurry in a short time. The performance of fs-laser irradiation assisted CMP was evaluated and possible effects including polishing efficiency and surface accuracy were investigated. Furthermore, surface analytical techniques XRD and XPS were carried out to analyze the mechanisms for improved polishing behavior. Experimental results indicate that three factors, namely, periodic rippled surface morphology, oxidation effect and an amorphous layer were demonstrated to play significant roles in better polishing performance. This study was a beneficial and significant exploration of expanding the application of high precision fs laser to CMP process.