Hot-wire produced atomic hydrogen: effects during and after amorphous-silicon deposition

The role of hot-wire atomic hydrogen during a-Si:H deposition is elucidated by investigating hydrogen diffusion into and within hot-wire deposited a-Si:H films. We exposed device-quality a-Si:H layers to atomic hydrogen in order to mimic the atomic hydrogen flux during deposition. Initially, exposure of as-deposited a-Si:H films leads to an enhancement of the hydrogen concentration by a factor of 2. A higher wire temperature or a longer duration of the atomic hydrogen exposure etches the silicon layer. The temperature of the films during these treatments was below the deposition temperature. Deposition of double layers which incorporate either H or D, shows considerable diffusion taking place at the substrate temperature which is usually applied for hot-wire a-Si:H layers in devices. The observation of these effects, the high atomic hydrogen flux and the high diffusion coefficient, indicate the important role of atomic hydrogen during hot-wire deposition.