High-rate sputtering of thick PZT thin films for MEMS

Crack and void free polycrystalline Lead Zirconate Titanate (PZT) thin films in the range of 5 µm to 10 µm have been successfully deposited on silicon substrates using a novel high rate sputtering process. The sputtered PZT layers show a high dielectric constant εr between 1,000 and 1,800 with a moderate dissipation factor tan (δ) = 0,002 − 0,01 measured at f = 1 kHz, a distinct ferroelectric hysteresis loop with a remanent polarisation of 17 µC/cm2 and coercive field strength of 5.4 kV/mm. The piezoelectric coefficients d33,f = 80 pm/V are measured by using a Double Beam Laser Interferometer (DBLI). Based on this deposition process a membrane actuator mainly consisting of a SOI layer and a sputtered PZT thin film was prepared. The deflection of this membrane actuator depending on the driving voltage was measured with a white light interferometer and compared to the results of finite element analysis (FEA). With this approach a transverse piezoelectric coefficient of about e31 = −11.2 C/m2 was calculated, whereas all the other material parameters in the model were lent from PZT-5A.