Plasma‐enhanced chemical vapor deposition of a‐SiC:H films from organosilicon precursors

A study of the growth of a‐SiC:H films by plasma‐enhanced chemical vapor deposition (PECVD) from two organosilicon precursors, silacyclobutane (H₂CH₂SiCH₂CH₂ or SCB) and methylsilane (CH₃SiH₃), is described. A capacitively coupled, parallel plate PECVD system was used to grow films at 250 °C and deposition pressure of 2.0 Torr. Standard (13.56 MHz) and low frequency (0.125 MHz) rf sources were used to generate the deposition plasma. Depositions were performed with and without argon dilution (neat) of the precursor. We report some of the first process/property relationships for organosilicon based a‐SiC:H films grown using a fixed, controlled set of deposition conditions. Included are data on film composition, structure, dielectric constant and stress. Films deposited from silacyclobutane had much higher carbon concentrations than those deposited from methylsilane, but in both cases the carbon fraction in the film was lower than that in the precursor. It is found that the plasma drive frequency has a stronger influence on film composition than argon dilution of the precursor during deposition. The low frequency plasma significantly increases the film growth rate for the neat precursor process. Depending on the growth process, the relative dielectric constants of the a‐SiC:H films ranged from 3.6 to 8.7. The variation of the dielectric constant over the frequency range 0.1–1000 kHz was negligible. All measured film stress was compressive and ranged from 0.1 to 1.0 GPa depending on precursor and plasma frequency. Films deposited from a 10% organosilicon/90% argon mixture showed higher dielectric constants, higher refractive indices and less bound hydrogen when compared to neat organosilicon precursor depositions. The films exhibited excellent oxidation resistance and could not be etched in 6:1 buffered HF solutions. The properties of the a‐SiC:H films are compared to PECVD hydrogenated silicon nitride and discussed in the context of applications requiring low temperature deposited protective dielectric coatings.