Rational Design of Si(B)Cn Microstructures Using Direct Photolithography of Patternable Preceramic Photoresists

Non-oxide ceramic MEMS based on Si, C, N and B elements are of great importance for high-temperature applications in harsh and oxidizing conditions including electronics, photonics and actuators. Yet, structuring and patterning ceramics is challenging and often relies on conventional soft-lithography or molding processes that can introduce defects and cracks leading to a decrease in the device’s performance. Herein, we report on the design of SiCN and for the first time SiBCN ceramic micro-components (in the 20-200 µm range) from direct patterning of tailor-made UV-curable polyvinylsilazane and polyborovinylsilazane preceramic resists, respectively. This approach first involves the chemical synthesis of patternable preceramic polymers through acrylate or methacrylate grafting onto poly(boro)vinylsilazane followed by subsequent crosslinking under UV light. FTIR and NMR spectroscopies confirmed the successful grafting of photocurable units on the preceramic polymers. UV spectroscopy allowed assessing the photosensitive properties of the resists while thermogravimetric analysis was used to monitor the polymer-to-ceramic conversion. SiCN and SiBCN micropatterns obtained after pyrolysis were thoroughly characterized by SEM, AFM and profilometry techniques. The Young’s modulus results for such microstructures (~ 60 GPa) are characteristic of good mechanical properties making these polymer-derived ceramics promising materials for MEMS applications.