Effect of Ar+ ion assist on the properties of a-C:H films deposited on a trench

In this study, a precursor gas mixture of toluene and Ar was used for the deposition of a-C:H films on a trench (20-mm pitch and 10-mm depth), and the effect of the Ar flow ratio on the film properties was investigated. The a-C:H films were deposited using a bipolar-type plasma based ion implantation and deposition technique under a negative pulse voltage of − 2 kV. The mechanical properties of the prepared a-C:H films, including internal stress, hardness and adhesion strength, were measured by means of surface profilometry, nanoindentation and a microscratch test, respectively. Furthermore, the microstructure of a-C:H films was evaluated by Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). The results showed that the thickness uniformity across the trench surface is improved by the addition of Ar, in particular, at an Ar flow ratio of 80%. The film on the top and bottom surfaces of the trench tends to change from a PLC to DLC structure with increasing Ar flow ratio, resulting in a significant improvement of mechanical properties. In the case of the sidewall, the film tends to change to a more GLC structure with increasing Ar flow ratio due to the Ar+ ion bombardment and sputtering effect.