On the micrometre precise mould filling of liquid polymer derived ceramic precursor for 300-µm-thick high aspect ratio ceramic MEMS

This paper describes a novel and scalable method for the fabrication of polymer derived ceramics (PDC) structures with high aspect ratio and micrometre scale features. Elastomeric micro-moulds composed of a filling pot are used to deliver via sacrificial micro-channels a precise amount of the liquid ceramic precursor to the target location with the micro-scale functional structures. To improve the filling properties of the mould and to ease the de-moulding of the fragile green body parts, we investigated various channel and mould coating materials, such as carbon and Teflon®-like C4F8. The coating properties were characterised by measuring the contact angle and the advancing speed of the PDC inside micro-channels. We found that, the C4F8 Teflon®-like coating yields the best de-moulding results for high aspect ratio moulds, whereas the carbon coating yields a two-fold increase in filling speed compared to bare PDMS. The fabricated samples and their side-wall properties were characterised in detail by means of optical and scanning electron microscopy. We present process parameters for well-defined ceramic samples containing micrometric features fabricated with this new approach opening the use of this outstanding material for new MEMS applications where resistance to harsh environment such as mechanical wear, high temperatures or corrosion is required. The presented fabrication method has the potential to be scalable up to cost-efficient mass production.