Backside wet etching of sapphire substrate by laser-induced carbothermal reduction

Abstract

Laser-induced backside wet etching is a promising technology to process sapphire substrate. However, the conventional working media including toxic organic and heavy metal salt solutions is not environmentally friendly. In this paper, the backside wet etching of sapphire substrate with ink as a working solution by laser-induced carbothermal reduction is achieved. Raman and XRD analyses demonstrate that ink can provide a stable carbon source and the carbothermal reduction of sapphire occurs during the etching. Numerical calculation reveals that the deposition of the carbon layer plays a crucial role in heating the sapphire to the temperature triggering the carbothermal reduction. The grooves etched by the laser-induced carbothermal reduction have smooth walls and good shape reproducibility. The linearly increase in etching depth with pulse number at the same laser fluence. The high-quality etching based on the carbothermal reduction as the etching mechanism is beneficial for fabricating microstructures on sapphire.