Growth evolution of Si:H prepared with SiH4 + Si2H6 as studied by real time spectroscopic ellipsometry

The effect of silane + disilane gas mixtures on the growth evolution of hydrogenated silicon (Si:H) thin films have been studied using in situ, real time spectroscopic ellipsometry during plasma enhanced chemical vapor deposition. Growth evolution diagrams were generated for fixed values of S (disilane-to-silane gas ratio) with variable R (hydrogen-to-reactive-gas ratio). Amorphous Si:H (a-Si:H) quality was found to degrade with increasing S, however R could be increased to maintain film quality. The growth rate of optimized a-Si:H material was stable with S, but a wider process parameter range for improved, but not fully-optimized, material was available at lower R with higher rates. Crystallinity was suppressed at higher values of S and lower values of R, but promoted with higher R at increased rates by potentially increasing the initial crystallite nucleation density.