Micromoulding of lead zirconate titanate (PZT) structures for MEMS

Abstract

Thick (>10 μm) ceramic structures for applications in micro-electromechanically systems are typically fabricated using screen printing techniques or by printing a continuous film and subsequently etching the structure. This work presents a thick film lift off technique to create high aspect ratio thick Lead Zirconate Titanate (PZT) features on silicon substrates. In this technique, a photoresist material is used to produce a mould, on a silicon substrate, and so define the shape of structures to be created. A composite sol gel ink (mixture of ceramic powder and sol) is then cast into the polymeric moulds and heat treated at low temperature (<250°C) to dry the ink. The use of these low temperatures means that the polymeric mould maintains its shape whilst still allowing the sol to be converted to an amorphous ceramic precursor. Subsequent deposition of further composite sol gel ink can then be used to increase the thickness of the features. The density of the structures can also be increased through the use of repeated sol infiltrations once the structure has been created. A final heat treatment is used to remove the polymeric moulds and crystallise the ceramic material.