AVS 52nd International Symposium
    Thin Films Wednesday Sessions
       Session TF-WeM

Paper TF-WeM3
Evaluation of Applied Substrate Bias on Yttria-Stabilized Zirconia Thin Films

Wednesday, November 2, 2005, 9:00 am, Room 306

Session: Mechanical and Tribological Properties of Thin Films
Presenter: J.R. Piascik, University of North Carolina at Chapel Hill and RTI International
Authors: J.R. Piascik, University of North Carolina at Chapel Hill and RTI International
J.Y. Thompson, University of North Carolina at Chapel Hill
C.A. Bower, RTI International
B.R. Stoner, RTI International and University of North Carolina at Chapel Hill
Correspondent: Click to Email
Partially stabilized zirconia (PSZ), possesses a unique set of material properties. Due to its high toughness, excellent wear behavior, and thermal stability, PSZ, in the form of thin films, can be used for a variety of applications ranging from biomedical to thermal barriers. The objective of this research was to study environmental effects on film stress and model water absorption into the defect structure of films deposited with varying substrate bias. Yttria (3 mol%)-stabilized zirconia (YSZ) thin films were deposited using radio frequency (RF) magnetron sputtering. YSZ thin films were deposited at a working pressure of 15mT, temperature of 150°C, and Ar/O2 gas ratio of 30:1. An applied substrate bias was varied (0 to 50W) to alter film density and structure. X-ray diffraction (XRD) showed that films increased in monoclinic phase percentage as a function of increasing substrate bias power. Wafer bow measurements indicate that initial film stress increased in a compressive direction (70 to 302MPa) as substrate bias was increased. Aging in ambient environments (25°C, 75% relative humidity) led to a significant increase in compressive stress (80MPa) for films deposited without substrate bias. Thermal treatment, to remove absorbed water, caused films to return to near-initial stress states. Once exposed to ambient conditions, measured stress was found to increase at a rate of 0.20MPa/min for the first 2hr of exposure then by approximately 2MPa/day for a period of 30 days. Films deposited with applied substrate bias displayed a reduction in this time-dependent phenomenon. Cross-sectional TEM allowed for high-resolution images to analyze film structure and defect density. A subsequent model is proposed, describing the incorporation of water vapor into structural defects in the deposited films. This work is supported through NIH-NIDCR R01 DE013511.