Hydrogen incorporation in the early stages of hydrogenated amorphous silicon deposition evaluated by real time infrared reflectance spectroscopy

We use real time, high sensitivity infrared reflectance spectroscopy to quantitatively study hydrogen incorporation during the growth of hydrogenated amorphous silicon by magnetron sputtering. For the range of deposition conditions studied (substrate temperature between 120 and 270°C and H ₂ partial pressure between 0.1 and 1.0 mTorr, which result in film hydrogen content between 10 and 30 at. %), hydrogen incorporation reaches steady state for film thickness, d≳25 Å. Deviations from uniform growth for d<25 Å are attributed to plasma-substrate interactions due to energetic hydrogen implantation tens of angstroms beneath the growing surface and changes in the surface area during nucleation and coalescence.