Post hydrogenation effect by hot wire method on poly-crystalline silicon based devices

Abstract

The effect of post hydrogenation by the hot-wire method on both bulk properties and TFT performance is studied and is compared with the effect of thermal annealing. In device applications, the passivation of defects is a key process for attaining high device performance. One of the most effective hydrogenation methods for poly-crystalline silicon and silicon based materials is the hot-wire technique. While the hydrogen concentration in the as-deposited poly-Si film fabricated by reactive thermal CVD is near 0.01%, it is found to increase to 0.6–0.7% by hydrogenation (at a temperature 200 °C) regardless of the crystalline fraction. The dangling bond density is observed to decrease from ∼3.5 × 10 18 to ∼9.0 × 10 17 cm −1. It also decreases by annealing in helium gas at temperatures exceeding 350 °C. The results suggest that hydrogenation by hot-wire method besides the passivation effect also creates dangling bonds, due to breaking of Si–Si bonds by highly reactive hydrogen.