Sic Thin Film Characterization and Stress Measurements for High Temperature Sensors Applications

Abstract

AbstractIn this work related to high temperature pressure sensors, a study was undertaken on the characterisation of β-SiC thin films through X-Ray Diffraction, AFM and stress measurements. 3C-SiC films were grown on (100) Si substrate in a vertical reactor by atmospheric-pressure chemical vapour deposition (APCVD). Silane and propane were used as precursor gas and hydrogen as carrier gas. Prior to the growth, Si surfaces were annealed at 1000°C for 5 minutes and carbonized with C3H8 at 1150°C during 10 minutes. At 1350°C, SiH4, C3H8 and H2 were introduced for the SiC deposition. The atomic ratio of Si/C in the gas phase was 0.3 and the growth rate was 3 μm/h. Only the process time was varying to obtain different SiC layer thicknesses varying from 3 to 9 μm as measured by FT-IR spectrometry. Stress measurements of thin β-SiC layers deposited on thick Si substrates were performed at room temperature using the bending plate method and the Stoney's equation. The stress for a 3 μm thick SiC layer is evaluated to be in the range of 400 MPa in tension. When increasing the SiC film thickness, this stress decreases due to the relaxation of the structure with bending. SiC/Si membranes were obtained by KOH etching and studied as a function of pressure in the [0-50 mbar] range. A residual stress in the membrane was deduced from the load-deflection measurement technique reaching 105 MPa in tension.