Mechanism and regulation of thermal damage on picosecond laser modification dicing of SiC wafer

Abstract

Picosecond laser modification dicing (PLMD), compared with blade dicing, is more suitable for high-efficiency and low-damage processing of high hardness and brittleness SiC materials. However, the potential thermal damage restricts the further promotion of PLMD technology. To solve this problem, in this paper, the thermal damage behavior and mechanism of PLMD are studied by means of experiment and molecular dynamics (MD) simulations. In sidewall, the thermal damage manifests as thermal decomposition and amorphization. The thermal decomposition, which is essentially the graphitization caused by the gasification of Si and enrichment of C, occurs in the atmospheric pressure modified layers. The amorphization, caused by 470.0 GPa high pressure and 1.58 × 1013K/s cooling rate, occurs in the high pressure modified layers. Other forms of thermal damage, including cracking, chipping, and oxidation, are caused by heat accumulation in kerf region. The focal overlap rate is refined through an intensity correction factor, then transformed into the effective pulse number, serving as input for the model. This contributes to model with an average accuracy of 81 %. By adopting a thermal damage regulation strategy, PLMD of SiC wafers without thermal damage is realized.