Replacement of PFAS Anti-Stiction Films in Inertial Sensors with Atomic Layer Deposition
ABSTRACT
Stiction presents a significant challenge in the MEMS and sensor industry, restricting design flexibility and defining maximum acceleration limits for inertial sensors. Reducing stiction can expand the operational range and reliability of these sensors. Currently, the industry relies on chemically inert layers, such as per- and polyfluoroalkyl substances (PFAS), to mitigate stiction. However, PFAS are linked to adverse health and environmental effects and are subject to stringent regulations and bans. As an industry, we bear the responsibility to minimize and eliminate PFAS usage wherever possible.
To that end, we have developed a robust, PFAS-free ceramic anti-stiction film applied via atomic layer deposition (ALD). ALD is a non-line-of-site vapor deposition technique capable of depositing high-quality films conformally on complex and challenging device architectures. Crystalline ALD films have shown significant stiction reduction for over a decade in laboratory settings. However, the challenge lies in their performance after device integration. Our goal is to provide a cost-effective solution suitable for high-volume manufacturing over multiple wafer bonding strategies. We have screened a range of ALD metal oxides, evaluating their properties, such as roughness, density, stress, and stiction performance, across device integration-relevant temperatures, ranging from 300 to 1000 °C.
This comprehensive study has resulted in a catalog of ALD film properties to aid the MEMS community in optimizing ALD anti-stiction film application. While most ALD anti-stiction films are <50 nm, we have also examined their impact on quality factor (Q) for various device architectures. Following the work of Kenny and colleagues, we aim to deconvolute the ALD film driven contributions of Q-loss, focusing on modeling thermoelastic dampening effects (TED) effects.
Collectively, these measurement and modelling efforts are crucial for integration and reliability testing of ALD anti-stiction films in GE Polaris platform-based inertial sensors.
BIOGRAPHY
Dr. Matt Weimer is Director of R&D at Forge Nano, where he drives innovation in semiconductor applications using atomic layer deposition (ALD). He earned his B.S. in Chemistry from the University of Washington and Ph.D. from the Illinois Institute of Technology, with a joint guest graduate appointment at Argonne National Laboratory (ANL). After completing his Ph.D., Matt's journey led him to a postdoctoral appointment at ANL in fundamental battery research, followed by a significant tenure at Lam Research, where he developed pioneering vapor-phase solutions for the semiconductor ecosystem, addressing both logic and memory applications.
At Forge Nano, Matt leads the discovery and development of novel ALD solutions across various semiconductor applications, including in the MEMS and sensor spaces. His research interests include surface chemistry modification, thin film growth and characterization, and technology commercialization. He has numerous publications, patents, and presentations in synthetic chemistry, ALD, and CVD. Matt also serves on the executive board of the Rocky Mountain Chapter of the American Vacuum Society (RMC AVS).
Outside the lab, Matt is an avid racquetball player, hiker, and traveler. He is also on the executive board of the Denver Center for Intercultural Scholars (DCIS) Foundation.