Growing demand of PZT films for MEMS applications requires scaling up from small scale fabrication to high volume production. Sputtered PZT films are good candidates for high volume manufacturing. Silex in cooperation with sputter tool producer (ULVAC, Inc) has over the last years developed capability to sputter high quality (BDV>75V/µm), long lifetime (~20 years at 60 V and 85 °C) PZT films. Available thicknesses are from 1 µm to 5 µm with consistent e31f = 15±1 C/m2. Increasing manufacturing volumes require more rigorous quality control of PZT films. Besides controls of PZT thickness, structure, piezoelectric performance Silex is monitoring lifetime of PZT. Lifetime definition is statistical measure of PZT performance. Another challenge is that evaluation of these critical parameters is only possible many mask layers downstream from the deposition. Understanding important properties, such as piezoelectric coefficient and TDDB lifetime, and how they connect to surface properties of underlying material and certain tool parameters and tool condition, is critical. The long feedback loop, together with the delicate deposition process, requires data structure and tool tracking beyond normal for a MEMS process. Even more important in a foundry environment where each individual product has its unique process flow contributing to the PZT film properties in the end product.
This knowledge enables Silex to not only depositing the PZT on wafers, but successfully integrated reliable PZT functionality to our foundry customer’s products. Silex pure-play strategy making devices for our customers has given us the opportunity to work with PZT in a wide range of applications, including ultrasound transducers, loudspeakers, inkjet printheads, scanning mirrors and more.