Influence of target direct current bias voltage on the film structure of hydrogenated microcrystalline silicon prepared by direct current-radiofrequency coupled magnetron sputtering

Hydrogenated microcrystalline silicon (μc-Si:H) films were prepared by direct current-radiofrequency (DC-RF) coupled magnetron sputtering using an argon/hydrogen gas mixture. X-ray diffraction (XRD) and Raman scattering spectra were measured and used to investigate the influence of the film structure on target DC bias voltage (Vb) during deposition. The deposition rate increased with decreasing Vb from 0 V to −500 V and with increasing RF power. The (111) XRD peak intensity and (111) mean crystallite size increased with decreasing Vb. In contrast, the (220) peak intensity and (220) mean crystallite size showed a maximum at Vb∼−300 V. The crystalline volume fraction also showed a maximum at Vb∼−300 V. These findings suggest that the kinetic energy of a sputtered silicon atom is very important in influencing the crystallinity of μc-Si:H films, and that control of target DC bias is very effective in preparing μc-Si:H films with a high degree of crystallinity.