Potential and limits of chemical enhanced deep cutting of silicon with a coupled laser-liquid jet

We present investigations on a new technology with which to cut wafers from it silicon ingot. i.e., the laser chemical processing (LCP), formerly known as laser chemical etching. A coupled laser-liquid jet is used to combine chemical and thermal processes for silicon ablation. We developed a numerical model to simulate heat transport and phase changes due to laser irradiation. Experiments with water and KOH solution as liquid media were performed. The results are discussed and compared with the simulations. It is shown that problems with the transport and redeposition of the thermally removed silicon in the groove are the reasons for the hitherto limited cutting depth. The potential of chemicals for in situ etching of the removed silicon are discussed in detail. The result of our work is the selection of suitable chemical systems namely. the perflourinated carbon compounds with dissolved chlorine its the etch medium. The LCP process thus developed promises to Cut very narrow and deep grooves and thus have the potential of a wafering application.