Mechanical Properties and Morphology of Polycrystalline 3C-SiC Films Deposited on Si and SiO 2 by LPCVD
- PDF / 2,715,045 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 41 Downloads / 179 Views
U11.3.1
Mechanical Properties and Morphology of Polycrystalline 3C-SiC Films Deposited on Si and SiO2 by LPCVD Xiao-an Fu, Jeremy Dunning, Srihari Rajgopal, Ming Zhang1, Christian A. Zorman, and Mehran Mehregany Department of Electrical Engineering and Computer Science 1 Department of Material Science and Engineering Case Western Reserve University, Cleveland, Ohio 44106, USA ABSTRACT Poly-SiC films were deposited on Si and SiO2 substrates in a high-throughput, low pressure chemical vapor deposition (LPCVD) furnace using dichlorosilane (DCS) and acetylene precursors. The deposition temperature and pressure were fixed at 900°C and 2 Torr, respectively, while the flow rate of DCS was varied between 18 and 54 sccm. Poly-SiC deposition rates on both Si and SiO2 were nearly identical to each other and increased as a function of DCS flow rate. Consistent with both substrate materials, the following observations were made. A slope change of the deposition rate versus DCS flow rate was observed around a DCS flow rate of 35 sccm. Residual stress varied with respect to the deposition rate, with tensile stresses occurring at lower deposition rates and compressive stresses at higher deposition rates. The tensile-to-compressive stress transition corresponded to the slope change of the deposition rate versus DCS flow rate. The surface morphology consisted of pyramidal grains, as observed under an SEM. TEM analysis for poly-SiC films grown on Si substrates showed that microstructural differences exist for poly-SiC films having tensile and compressive stresses.
INTRODUCTION SiC is an exceptionally attractive material for microelectromechanical systems (MEMS) because of its outstanding mechanical, chemical and electrical properties as documented in the scientific literature [1-3]. Currently, polysilicon is the dominant MEMS material, partially because of its high throughput deposition processes and favorable electrical and mechanical properties. Recently, advances in LPCVD methods have resulted in a polycrystalline 3C-SiC (poly-SiC) deposition technology that is comparable with polysilicon in terms of throughput [4]. Previous work on polycrystalline 3C-SiC (poly-SiC) films deposited by atmospheric pressure chemical vapor deposition (APCVD) indicates that the substrate materials influence the microstructure and surface morphology of the deposited poly-SiC films [5]. In this work, the residual stress, surface morphology, and microstructure of poly-SiC thin films grown on Si and SiO2 by LPCVD were examined. With both substrate materials, a consistent relationship between the SiC deposition rate and the as-deposited film stress was observed, with tensile stresses occurring at lower deposition rates and compressive stresses at higher deposition rates. A slope change in the deposition rate versus DCS flow rate was observed around a DCS flow rate of 35 sccm. A transition from tensile to compressive stress corresponded to the slope change of deposition rate versus DCS flow rate also occurred.
U11.3.2
EXPERIMENTAL DETAILS SiC films were
Data Loading...
