Deposition mechanism of hydrogenated amorphous carbon film by C₃H₆/H₂ mixture gas plasma

Hydrogenated amorphous carbon (a-C:H) thin films as a hard mask for plasma etching were deposited by a plasma-enhanced chemical vapor deposition using C₃H₆/H₂. The residual compressive stress a-C:H films once decreased with increasing a hydrogen (H₂) flow rate ratio from 0.00 to 0.50, then it increased at the H₂ flow rate ratios above 0.50. As a result, the residual compressive stress showed the minimum value at a H₂ flow rate ratio of 0.5. According to Raman spectra, it was suggested that residual stress depends on the sp³ C-C contents in the a-C:H films. This is also consistent the maximum film density estimated using elastic recoil detection analysis (ERDA) and nuclear reaction analysis (NRA). On the other hand, the etching rates of a-C:H films deposited at H₂ flow rate ratios of 0.25 and 0.75 were similar, but their film densities were 2.03 and 1.85 g/cm³, respectively. This is suggested that not only the film density but also its structure contributes to the etching resistance.