Silicon carbide and amorphous carbon film formation by plasma immersion ion implantation: a comparison of methane and toluene as plasma forming gases

In the present study a comparison of two different hydrocarbon precursor gases, namely methane and toluene, on the formation of silicon carbide (SiC) and amorphous carbon (a-C:H) films by plasma immersion ion implantation (PIII) of silicon is made. The samples are analyzed by using Rutherford backscattering spectrometry (RBS) and X-ray photoelectron spectroscopy (XPS) for their element composition. XPS and Raman spectroscopy are applied to determine the bonding of silicon and carbon. Depending on the number of high voltage pulses the samples have been treated with, which corresponds to the ion fluence, it is possible to form stoichiometric SiC films without C layers on top of the wafers if methane is used as plasma forming species. For the same process conditions, CH4 PIII always results in thicker SiC and thinner a-C:H films compared with C7H8 PIII. SiC bond formation is proven by XPS. Raman spectroscopy shows the formation of a-C:H films for high pulse numbers for the case of a methane plasma, but already for small pulse numbers if toluene is used for plasma forming species.