Heavily Doped Polycrystalline 3C-SiC Growth on SiO_2/Si (100) Substrates for Resonator Applications

摘要

3C-SiC is a promising material for the development of microelectromechanical systems (MEMS) applications in harsh environments. This paper presents the LPCVD growth of heavily nitrogen doped polycrystalline 3C-SiC films on Si wafers with 2.0 μm-thick silicon dioxide (SiO_2) films for resonator applications. The growth has been performed via chemical vapor deposition using SiH_4 and C_2H_4 precursor gases with carrier gas of H_2 in a newly developed vertical CVD chamber. NH_3 was used as n-type dopant. 3C-SiC films were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), secondary ion mass spectroscopy (SIMS), and room temperature Hall Effect measurements. It was shown that there is no voids at the interface between 3C-SiC and SiO_2. Undoped 3C-SiC films show n-type conduction with resisitivity, Hall mobility, and carrier concentration at room temperature of about 0.56 Ω·cm, 54 cm~2/Vs, and 2.0×10~(17) cm~(-3), respectively. The heavily nitrogen doped polycrystalline 3C-SiC with the resisitivity of less than 10~(-3) Ω·cm was obtained by in-situ doping. Polycrystalline SiC resonators have been fabricated preliminarily on these heavily doped SiC films with thickness of about 2 μm. Resonant frequency of 49.1 KHz was obtained under atmospheric pressure.