Microstructure and electrical properties of nitrogen doped 3C–SiC thin films deposited using methyltrichlorosilane

Abstract

The growth, microstructure and electrical properties of in-situ nitrogen doped 3C–SiC (111) thin films for sensor applications are presented in this paper. These thin films are deposited at a pressure of 2.5mbar and temperature of 1040°C on thermally oxidized Si (100) substrates from methyltrichlorosilane (MTS) precursor using a hot wall vertical low pressure chemical vapor deposition (LPCVD) reactor. Ammonia (NH3) is used as the nitrogen doping gas. The sensor response depends on chemical composition, structure, morphology and operating temperature. The above properties are investigated for all in situ nitrogen doped (0, 9, 17 and 30at% of nitrogen) 3C–SiC thin films using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and four probe method. The XRD patterns of the 3C–SiC thin films show a decrease in the crystallinity and intensity of the peak with increase in dopant concentration from 0 to 17at%. AFM investigations show an improvement in the grain size of the nitrogen doped 3C–SiC thin films with increase in nitrogen concentration from 0 to 17at%. The sheet resistance of nitrogen doped 3C–SiC thin films is measured by the four probe technique and it is found to decrease with increase in temperature in the range of 40–550°C. The resistivity and average temperature coefficient of resistance (TCR) of doped 3C–SiC thin film deposited with 17at% of nitrogen concentration are found to be 0.14Ωcm and −103ppm/°C, respectively and this can be used as a sensing material for high temperature applications.