Processing of silicon by Nd: YAG-lasers with harmonics generation

摘要

Micro structures in silicon are applied in different fields of industry, medicine and research. Examples are micro mechanical sensors for car security systems, nozzle plates for printer, and optical elements for X-ray beam splitting. Wherever the accuracy of etched silicon structures is not required, laser processes with short pulses and small wave length can be an option with the advantage of shorter process tune High quality cutting and drilling of silicon can be achieved by application of diode pumped q-switched Nd:YAG-lasers and harmonics generation. The short pulses (15 ns) and the UV wave length (355 nm) of the Gator UV from Lambda Physik AG, for example, allow a reduction of thermal effects like deposition of molten material and heat effected zones at the edges. Especially in the case of deep structures the ablation plasma causes powerful heating of the walls. An reduction of the plasma temperatures and so the heat influence on the walls can be realized by a small laser wave length with low plasma absorption. Short laser pulse durations are necessary to reduce the heat effected depth or melting due to heat flow from the ablation area into the bulk material. Also the duration and intensity of plasma heating is reduced by short laser pulses. In this contribution the possibilities and limits of laser machining of Si by diode pumped Nd:YAG-lasers with harmonics generation will be presented by means of structures processed by application of a scanner with f-theta-optic. The results will be discussed concerning the experimental setup and the laser parameters.