Direct-Write Laser Grayscale Lithography for Multilayer Lead Zirconate Titanate Thin Films

Direct-write laser grayscale lithography has been used to facilitate a single-step patterning technique for multilayer lead zirconate titanate (PZT) thin films. A 2.55- $\mu \text{m}$ -thick photoresist was patterned with a direct-write laser. The intensity of the laser was varied to create both tiered and sloped structures that are subsequently transferred into multilayer PZT(52/48) stacks using a single Ar ion-mill etch. Traditional processing requires a separate photolithography step and an ion mill etch for each layer of the substrate, which can be costly and time consuming. The novel process allows access to buried electrode layers in the multilayer stack in a single photolithography step. The grayscale process was demonstrated on three 150-mm diameter Si substrates configured with a 0.5- $\mu \text{m}$ -thick SiO2 elastic layer, a base electrode of Pt/TiO2, and a stack of four PZT(52/48) thin films of either 0.25- $\mu \text{m}$ thickness per layer or 0.50- $\mu \text{m}$ thickness per layer, and using either Pt or IrO2 electrodes above and below each layer. Stacked capacitor structures were patterned and results will be reported on the ferroelectric and electromechanical properties using various wiring configurations and compared to comparable single layer PZT configurations.