Preparation and characterization of wafer scale lead zirconate titanate film for MEMS application

In this paper, 1.9 μm-thick crack-free Pb(Zr,Ti)O₃ (PZT) film was successfully prepared on 4-in. Pt/Ti/SiO₂/Si wafer by sol-gel technique. A platinum/titanium (Pt/Ti) layer was sputtered on backside of the wafer to balance the residual stress during heat-treatment process. The microstructures, electric properties, piezoelectric properties and mechanic properties of the as-deposited PZT films were investigated. The effects of heating-rate in rapid thermal annealing on film crystallization and film properties were discussed. It was found that the wafer-bending after PZT film deposition can be effectively reduced from -40.5 to -12.9 μm by using the stress balance layer. According to scanning electron microscopy images and X-ray diffraction patterns, the as-deposited PZT films exhibited preferred columnar structure, which strongly oriented in (1 0 0). Furthermore, when the heating-rate was set at 3.5 °C/s, the film showed higher piezoelectric constant d₃₃ (143 pm/V) and higher hardness H (∼9 GPa). While when the heating-rate was set at 10.5 °C/s, the film exhibited larger dielectric constant ε (1 3 1 0), higher remanent polarization P_r (39.8 μC/cm²) and higher apparent modulus E_a (∼120 GPa) by taking advantage of shorter crystallization and grain-growth period.