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 T_g, the apparent activation energy of crystallisation E_a 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 25μm for MEMS applications.