Ion bombardment and temperature effects on the microstructure of RF plasmachemical 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 whi le the substrate was heated to between 453 and 853 K. The electrical parame ters of the discharge, RF current and voltage, and DC bias permit the deter mination 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 en ergy can rise 300 eV at 853 K while the discharge current does not depend o n the biased electrode temperature. At high temperature and RF power, high ion energy and flux lead to a competition between growth and etching. Furth ermore, we observe that ion energy and substrate temperature (T-substrate) act in an opposite way on the Si/C ratio in the deposit: an increase in T-s ubstrate leads to an increase in Si/C, whereas, on the contrary, the ion en ergy limits this ratio. An energy threshold (E-ion max congruent to 140 eV) leading to the decrease in this ratio is evidenced. The film contains C-Si , C-C Sp(2), C-C Sp(3) and hydrogen bonds, whose respective contributions a re dependent on the ion energy and are related to the hardness values, rang ing from 16 to 29 GPa. The growth of hard SiC-based coatings (congruent to 20 GPa) below 200 degreesC is highlighted. (C) 2001 Elsevier Science B.V. A ll rights reserved.