Using Fluorine-Ion Implanted a-Si Layer to Reduce Ni Contamination and Passivate the Defects in NILC Poly-Si

Abstract

Polycrystalline silicon thin-film transistors (poly-Si TFTs) have been widely used in active matrix organic liquid crystal displays (AMOLCDs) because their higher carrier mobility and lower threshold voltage than conventional amorphous thin-film transistors (a-Si TFTs). Ni-metal-induced lateral crystallization (NILC) is one of these effective methods that can reduce the crystallization temperature to fabricate poly-Si TFTs on inexpensive glass substrates. However, the poly-Si grain boundaries which included dangling bonds would trap Ni and NiSi2 precipitates. This phenomenon resulted in threshold voltage shifting and lower field-effect mobility. In order to reduce the Ni contamination and passivate the dangling bonds in the active layer, the a-Si layer with fluorine-ion implanted was used as gettering layer (F-G layer) to resolve the issue. In the gettering process, Ni precipitates would diffuse to the fluorine-ion implanted a-Si layer because of the concentration gradation difference. Concurrently, fluorine-ion also diffused into the active layer and passivated the dangling bonds which associated with trap states density.