Polymer derived ceramic microparts from X-ray lithography—cross-linking behavior and process optimization

Abstract

The fabrication of micro components made from ceramic materials is becoming more and more important because of their outstanding chemical stability. Different replication methods like low or high-pressure injection molding of ceramic feedstocks have been established. Various lithographic methods are being widely used for the direct fabrication of very precise plastic or metal micro structured surfaces. The presented work deals with the direct manufacturing of microstructures by using ceramic precursors in combination with X-ray lithography. This allows for a rapid fabrication of micro structured plastic components that are stable at high temperatures (400 °C), chemically resistant and transparent. Pyrolysis of these parts yields amorphous Si C N or Si 3N 4 ceramics. The applicability of different preceramic polymers based on polysilazane for direct structuring with synchrotron radiation was investigated. X-ray exposures of polysilazane polymer filled with Si 3N 4 ceramic powders were carried out, showing that it is possible to microstructure those composites. By inserting ceramic fillers, a reduction of the shrinkage during pyrolysis was possible. Further investigations were made to determine the maximum filler content, the required exposure dose and the cross-linking mechanism using IR- and NMR-spectroscopy. As established in the LIGA technique with PMMA, resist layers up to 1 mm should be possible by deep X-ray lithography on preceramic polymers. Admittedly for the pyrolytic conversion into the amorphous SiCN ceramic, film thickness should be limited as crack formation is deteriorating with increasing dimensions.