Laser micromachining of silicon in air and ice layer

Abstract Thermal damage is an important drawback of laser micromachining process, and several techniques have been developed to control and limit heat induced by laser during the ablation. A novel method presented in this study is to perform the laser micromachining in ice, where the ablation take places while a workpiece is cooled in a thin ice layer. This technique is expected to limit the excessive heat conducting toward the workpiece material and also to prevent the cut debris depositing in the work surface as usually found in the dry laser ablation. Silicon wafer was used as a work sample to be cut in this study. The effects of ice temperature, ice layer thickness and average laser power on cut dimensions were experimentally investigated, and the predictive models for cut width and depth based on energy balance theorem were also formulated in this paper. Although some optical disturbances due to ice-water-vapor transitions limited the cut depth obtained, a clean and narrow cut with small taper angle was achievable when silicon was cut in ice layer. According to the findings of this study, the ice-assisted laser micromachining process could be a promising method for minimizing thermal damage in the laser ablation of silicon. In addition, this technique could also be of high potential for processing other heat-sensitive materials for micro-manufacturing applications.