Effects of activated reactive evaporation process parameters on the microhardness of polycrystalline silicon carbide thin films

Abstract

Polycrystalline ß-SiC is expected to be an excellent material for thin film temperature sensors for the measurement of the surface temperature of gas turbine engine components operated at high temperatures (up to 1500°C). In this paper, Vickers and Knoop indentation microhardness tests were carried out on the silicon carbide films grown on Si(100) substrates by the activated reactive evaporation (ARE) process to measure one of the important mechanical properties, i.e. hardness of the films. The results of these tests are presented as a function of the ARE process parameters, such as C2H2 pressure PC2H2, substrate temperature Tsub, ARE electrode voltage VARE for the generation of d.c. glow discharge and substrate bias Vsub. It was found that the hardness of the films is very much dependent on these process parameters. A Vickers hardness value of 3680 kgf mm−2 (36.1 GPa) at 25 gf load (0.25 N) and a Knoop hardness value of 2060 kgf mm−2 (20.2 GPa) at 100 gf load (0.98 N) are obtained for polycrystalline ß-SiC films (C-to-Si ratio, 1.17) prepared under the following deposition conditions: C2H2 pressure, 3 mTorr (0.4 Pa); substrate temperature, 700°C; ARE electrode voltage, +150 V; substrate bias, −50 V.Microhardness variation of the ß-SiC films with applied load on the indenter was also studied. It was found that the hardness of the films decreases with increasing load, which is believed to be due to indentation size and substrate hardness effects.