Effects of carbon additions on crystallinity and resistivity in Si–C–H thin films deposited by CVDs

The Si–C–H thin films were deposited at 300 °C by plasma enhanced chemical vapor deposition (PECVD) and around 600 °C by pyrolysis CVD, in which C2H4 and SiH4 were used as the resource gases and hydrogen as the carrying vehicle. The formation of micro-crystals in the Si–C–H films was investigated by TEM, IR spectroscopy and electrical resistivity measurements. The results show that many silicon nano-crystalline particles are embedded and distributed uniformly in the amorphous matrix of the Si–C–H thin film. A higher content of C2H4 results in a lower crystallinity of the film deposited both by PECVD and pyrolysis CVD. The crystal grows more easily in the film deposited with C2H4–SiH4 at high temperature around 600 °C by pyrolysis CVD than that deposited at 300 °C by PECVD. The resistivity of the film by pyrolysis CVD at high deposition temperature is about five orders of magnitude lower than that by PECVD at low deposition temperature. The SiC crystalline phase trends to form quite possibly in the Si–C–H thin film deposited at 630 °C by pyrolysis CVD. The expressions of the crystallinity and resistivity as functions of the content of C2H4 are theoretically deduced. The theoretical curves are showed to be very coincident with the experimental results in the Si–C–H thin film. The crystallinity of the film rests mainly with the nucleation rate of silicon phase that is dependent on the content of C2H4 in deposition source gases. The resistivity behavior of Si–C–H thin film matches with the parallel model of the two phase events, where the contribution of crystalline phase is appropriate to the contact probability among the silicon crystals and compatible with homogeneous distribution of the particles embedded in matrix. [Copyright &y& Elsevier]