A novel self-aligned offset-gated polysilicon TFT using high-κ dielectric spacers

Abstract

In this letter, a novel self-aligned offset-gated Poly-Si thin-film transistor (TFT) using high-κ dielectric Hafnium oxide (HfO2) spacers is proposed and demonstrated. The HfO2 film is deposited by magnetron sputter deposition, and the HfO2 spacers are formed by reactive ion etching. The permittivity of the deposited HfO2 is approximately 20. Experimental results show that with the high vertical field induced underneath the high-κ spacers, an inversion layer is formed, and it effectively increases the on-state current while still maintaining a low leakage current in the off-state, compared to the conventional lightly doped drain or oxide spacer TFTs. The on-state current in the offset-gated Poly-Si TFT using the HfO2 spacers is approximately two times higher than that of the conventional oxide spacer TFT.