Short-pulse and short-wavelength ablation of semiconductor materials

Increasing miniaturization and integration of multiple functions into portable electronic devices and sensors ask for smaller electrical components. Conventional abrasive processes often reach their technological limit resulting in the demand for alternative technologies with increased precision and performance. Lasers have been proven to be a suitable tool for micromachining, but often suffering the disadvantage of heat or shock affected zones around the machined structures. To be feasible as an industrial solution, new approaches have to provide very high precision and process stability with minimal collateral damage. Presently, two different approaches for laser machining of semiconductor materials are being investigated. Although the interaction mechanism is completely different as described within this paper, both are regarded as promising technologies: ultrashort-pulse and short wavelength laser machining. Femtosecond laser machining has been used for a variety of applications, showing the advantage of non-thermal ablation of many kinds of materials. Due to the short pulse duration and the high intensities multi-photon absorption allows to overcome the bandgap of semiconductors while not affecting the bulk material. Due to the short wavelength excimer lasers as well as fluorine lasers provide the general ability to generate small spot sizes and emit photons with higher energies compared to the bandgap of the material, e.g. of silicon. Both technologies will be discussed and compared, and applications for micro-machining of silicon will be presented.