ChEMS Department Seminar

Event Date/Time
Event Location
https://msu.zoom.us/j/98064211809
Password: Seminar
Speaker
Eric Chason
Event Description
Origins of Residual Stress during Thin Film Growth

 

Abstract

There is a long history of studying stress in thin films. A wide range of phenomenology has been observed showing a complex dependence on growth rate, temperature, microstructural evolution and particle energy.  The experiments bring up interesting questions about the underlying kinetic processes that determine stress. For instance, why does it change form tensile to compressive in many metal films as they get thicker? Or why does a film grow with tensile stress at low temperatures but with compressive stress at higher temperatures? To address observations such as these, we describe a model that considers multiple mechanisms for generating and relaxing stress during film growth. These relate the stress to fundamental materials processes such as grain boundary formation, adatom diffusion, grain growth and defect formation.  The resulting equations describe the stress evolution as a function of thickness so that the model can be directly compared with real-time wafer curvature measurements. Examples for numerous materials, deposition processes and processing conditions will show how we are beginning to develop a comprehensive understanding of thin film stress that will allow us to control and predict it.

Bio

Eric Chason is a professor in the School of Engineering at Brown University. He received his Ph.D. degree in physics in 1985 from Harvard University. After one year of post-doctoral research at Gakushuin University in Japan, he joined Sandia National Laboratories in 1987 and became a senior member of the technical staff. He became a member of the Brown faculty in 1998.

Chason’s research focuses on the evolution of surfaces and thin films during materials processing. This work has led to the development of several in situ thin film diagnostics that enable the monitoring of thin film stress, surface morphology, microstructure and interfacial reactions during film growth and ion bombardment. This includes the development of a multi-beam optical technique for monitoring stress evolution in situ during processing.  In recent years, his research projects have included residual stress in polycrystalline films, whisker formation in Sn films, stress and phase evolution in Li-ion batteries and ion-induced surface nano-patterning.