MICROMECHANICS VIA X-RAY ASSISTED PROCESSING

The application potential of micromechanics is very large and falls in to very-large-scale-integration-like markets such as magnetic recordin g and electromechanical components and application specific markets su ch as surgery tools and sensors. Many of these markets cannot now be a ddressed because cost effective fabrication technology is not now avai lable to fabricate the required highly complex devices. Idealized fabr ication tools must address three dimensional processing with tolerance s in the 100 ppm range and must extend over a large material base. The y must do that with some integrated circuit-cofabrication compatibilit y in a cost effective manner. There is a premium for tools which can h andle large structural heights with small critical dimensions. X-ray a ssisted processing can satisfy some of the requirements of the idealiz ed tool. X-ray assisted processing started with the basic LIGA process in Germany. This process can be extended by merging it with surface m icromachining and assembly. The current versions of LIGA and LIGA-like processing are restricted in performance by photoresist strain which is typically found in thick photoresist processes. Photoresist strain can and has been reduced significantly by introducing solvent bonded p hotoresist application procedures which are followed by precision mill ing and polishing. This extends allowed photoresist thicknesses to hei ghts in the centimeter range. Exposure via synchrotron generated x-ray fluxes and subsequent developing has produced structures with structu ral heights to 1 cm. This implies that x-ray assisted processing does not only play a major role in micromechanical fabrication but also in precision engineering. This statement is further supported by results that indicate that multiple x-ray mask processes are feasible and that plastic parts can be fabricated by direct x-ray exposure over large s urface areas without injection molding. Test vehicles for x-ray assist ed processing at the University of Wisconsin fall into two categories: modular micromechanical building blocks such as gear boxes and novel sensors such as high speed magnetic micromotors.