Lift-off process of piezoelectric lead-zirconate-titanate thin film using self-assembled monolayer as sacrificial layer

In this work, a hydrophobic self-assembled monolayer, perfluorodecyltrichlorosilane (FDTS) (CF₃(CF₂)₇(CH2)₂SiCl₃), was proposed as a sacrificial layer for a lift-off process of a piezoelectric lead-zirconate-titanate (PZT) thin film on a Pt/Ti/SiO₂/Si substrate. A FDTS fine pattern was firstly vapour deposited on a Pt/Ti/SiO₂/Si substrate by a lift-off process, and then the PZT precursor was spin-coated on the Pt/Ti/SiO₂/Si substrate, post-baked so the solvent decomposed and evaporated and annealed for crystallisation. The experimental results demonstrated that the super-hydrophobic FDTS with a contact angle of >120° is effective in preventing PZT crystallisation because of its thermal stability during PZT post-baking, and its barrier-effects between the spin-coated PZT precursor and the Pt/Ti substrate. After removing the FDTS and the PZT which is on top of the FDTS by a second lift-off process using ultrasonic agitation, a PZT fine pattern was successfully obtained on the Pt/Ti/SiO₂/Si substrate with a thickness of 200-300 nm and feature size of a few tens of microns. In this Letter, the hydrophobic properties and surface morphology of different types of FDTS were studied and its barrier-effect on PZT crystallisation were analysed. The effects of PZT thickness in each spin-coating to lift-off the and PZT properties were investigated. The obtained PZT pattern was evaluated by an X-ray diffraction measurement.