Wet-etch patterning of lead zirconate titanate (PZT) thick films for microelectromechanical systems (MEMS) applications

Lead zirconate titanate (PZT) films are very attractive for microelectromechanical systems (MEMS) applications because of their high piezoelectric coefficients and good electromechanical coupling. In this work, wet-etch patterning of sol-gel PZT films for MEMS applications, typically with film thicknesses ranging from 2 to 10 microns, was studied. A two-step wet-etch process was developed. In the first step, 10:1 buffered HF is used to remove the majority of the film at room temperature. Then a solution of 2HCl:H₂O at 45 °C is used to remove metal-fluoride residues remaining from the first step. This enabled successful patterning of PZT films up to 8 microns thick. A high etch rate (0.13μm/min), high selectivity with respect to photoresist, and limited undercutting (2:1 lateral:thickness) were obtained. The processed PZT films have a relative permittivity of 1000, dielectric loss of 1.6%, remanent polarization (P_r) of 24μC/cm², and coercive field (E_c) of 42.1 kV/cm, all similar to those of unpatterned films of the same thickness.