Evaluation f a Rapid Prototyping Process for Silicon Microstructures

摘要

During the last decade rapid prototyping has made a tremendous success in almost every branch of industrial fabrication. Almost every article of today's life is pre-fabricated in a rapid process during its design. Functional rapid prototypes represent an increasing share, as they allow realistic functional tests of a component in an early stage of development. MEMS technology is still at the beginning of the rapid prototyping area. Up to now, only a few conventional techniques, like stereolithography, have been downscaled to create rapid microrototypes with a limited choice of materials and geometries. Rapid prototyping of silicon is completely out of reach today. In this paper we propose a micro rapid prototyping concept for functional silicon microstructures. The process combines laser technology with standard processes of silicon microstructuring and has been evaluated with a metal-silicon layer system. First, noble metal is vapour deposited on top of a silicon wafer. The metal is subsequently structured with a laser, thus creating a mask, which can be transferred into the silicon by standard chemical etching procedures like KOH-etch. The advantage of this concept is that the time-consuming photomask generation is omitted completely, as the laser can be guided with CAD data. Moreover, the standard structuring process gives the opportunity to gain a microstructure with features equivalent to the final component. With laser ablation and KOH-etch two process steps are being carried out subsequently, which are inevitably linked to each other. Depending on the energy of the laser irradiation the ablation performance changes and, with it, the minimal structure width and the thermal melting zone at the edges of the mask openings. If the energy density is too high the crystalline structure of the silicon is destroyed by heat transfer and heat conduction. Hereby the anisotropic etch resistance is lost, which influences the following KOH-each process. At the current state the process is monitored and optimised for different values of laser energy density. In this progress report the optimisation and the principal feasibility will be shown with simple micromechanic and microfluidic structures.