Ion bombardment and temperature effects on the microstructure of RF plasma chemical vapor-deposited SiC:H

A tetramethylsilane [Si(CH3)4]/argon mixture was used for the deposition of silicon carbide-based films under various degrees of ion bombardment while the substrate was heated to between 453 and 853 K. The electrical parameters of the discharge, RF current and voltage, and DC bias permit the determination of the action of the energy and flux of ions impinging the growing film surface. In the power range investigated (0–55 W), the maximum ion energy can rise 300 eV at 853 K while the discharge current does not depend on the biased electrode temperature. At high temperature and RF power, high ion energy and flux lead to a competition between growth and etching. Furthermore, we observe that ion energy and substrate temperature (Tsubstrate) act in an opposite way on the Si/C ratio in the deposit: an increase in Tsubstrate leads to an increase in Si/C, whereas, on the contrary, the ion energy limits this ratio. An energy threshold (Eion max≅140 eV) leading to the decrease in this ratio is evidenced. The film contains CSi, CC sp2, CC sp3 and hydrogen bonds, whose respective contributions are dependent on the ion energy and are related to the hardness values, ranging from 16 to 29 GPa. The growth of hard SiC-based coatings (≅20 GPa) below 200°C is highlighted.