Stability of a-Si:H TFTs Employing APCVD SiO 2 with N 2 Plasma Treatment as a Gate Dielectric

We have investigated the stability of the hydogenated amorphous silicon thin film transistors (a-Si:H TFTs) employing silicon dioxide (SiO2) with N2 plasma treatment as a gate dielectric, where SiO2 was deposited by atmospheric pressure chemical vapor deposition (APCVD). Their stability was compared with those of a-Si:H TFTs whose gate dielectric was silicon nitride (SiNx) deposited by plasma enhanced chemical vapor deposition (PECVD). Two kinds of stresses, gate bias and light illumination, were applied. The threshold voltage shin (AVu,) and the inverse subthreshold slope shift (ΔVfac) were measured as a function of the bias voltage and the light stress time. For the positive bias stress, the ΔVth, of the a-Si:H TFTs with the N2 plasma treated SiO2 dielectric is smaller than that with the PECVD SiNx gate dielectric. For the negative bias stress and light stress, however, the ΔVth of TFT with N2 plasma treated SiO2 dielectric is larger than that with the SiNx dielectric