Crystallisation of Foturan® glass–ceramics

Photostructurable glass–ceramics are suitable for 3-dimensional microfabrication and, in some instances, can be used as an alternative material to silicon in the microfabrication of micro-electro-mechanical-system (MEMS) devices. Foturan® is a photosensitive lithium–aluminium–silicate glass that can be structured by an exposure to UV light, followed by a thermal treatment and an etching step. In this work, the crystallisation kinetics and microstructure evolution of unexposed and UV-exposed Foturan® are investigated by means of differential scanning calorimetry, X-ray diffraction and scanning electron microscopy. The glass transition temperature Tg, the apparent activation energy of crystallisation Ea and the colour of UV-exposed Foturan® are discussed. It is shown that nucleation and crystallisation of UV-exposed Foturan® can be steered either as a function of temperature (non-isothermal) or as a function of time (isothermal). This is essential for the photostructuring and etching of Foturan® regarding the achievable feature sizes of 25 μm for MEMS applications.