Elimination of PZT thin film breakage caused by electric current arcing and intrinsic differential strains during poling

Abstract

Historically, substrate breakage during the poling process has been responsible for a 2% yield loss for a contract manufacturer specializing in volume production of lead zirconate titatate (PZT) thin film devices. In this research, two major causes of poling breakage were identified. First, stresses along substrate edges make PZT substrates more susceptible to breakage if any sort of mechanical force is present. It was determined that these stresses were caused by differential strains due to incomplete metal layer coverage. Second, the electrical arcing that is frequently taking place during poling sends a mechanical shock wave through the substrate. Electrical arcing is caused by metal overspray during the sputtering process. Poling breakage was experimentally reduced by 70% by redesigning the shadow mask used during sputtering to eliminate any metal overspray.