Application of HfO2 high-k gate insulator for excimer laser annealed poly-Si TFT

Abstract

The electrical characteristics of polycrystalline silicon (poly-Si) thin film transistor (TFT) crystallized by excimer laser annealing (ELA) method with high-k gate dielectrics were evaluated. Because a high thermal budget is inevitable for conventional fabricating process of poly-Si TFTs, an amorphous silicon film on a buried oxide was crystallized by annealing with a KrF excimer laser (248) to fabricate a poly-Si film at low temperature. Furthermore, the high permittivity HfO2 film with a thickness of 20 nm as the gate-insulator was deposited by atomic layer deposition (ALD) to low temperature process. In addition, the solid phase crystallization (SPC) was compared to the ELA method as a crystallization technique of amorphous-silicon film. As a result, the crystallinity and surface roughness of poly-Si crystallized by ELA method was superior to the SPC method. Also, we obtained excellent device characteristics from the poly-Si TFT fabricated by the ELA crystallization method.