Impact of N2O Plasma Reactant on PEALD-SiO2 Insulator for Remarkably Reliable ALD-Oxide Semiconductor TFTs

We studied nitrogen (N) incorporation effects on the electrical characteristics of SiO
₂
fabricated by plasma-enhanced atomic layer deposition (PEALD). To determine whether N could be incorporated into the SiO
₂
, nitrous oxide (N
₂
O) plasma with different plasma powers (100, 150, and 200 W) was used during the SiO
₂
deposition, and the film properties were compared with SiO
₂
fabricated using a conventional oxygen (O
₂
) plasma reactant. Compared to the O
₂
plasma reactant, the hard breakdown is improved by 27.5% as N
₂
O plasma power increases up to 150 W, whereas it is degraded at a N
₂
O plasma power of 200 W. These results are found to describe the relationship between the N content and film properties. The N content in the SiO
₂
films fabricated using increasing N
₂
O plasma power of 100, 150, and 200 W gradually increased by 0.2%, 0.4%, and 0.5%, respectively. However, the N
₂
O plasma power of 200 W results in increased O deficient Si bonding. To investigate the effects of continuous plasma exposure at the bottom layer during the SiO
₂
deposition, we fabricated indium–zinc oxide (IZO) top-gate bottom-contact (TG-BC) thin-film transistors (TFTs) using the SiO
₂
as a gate insulator (G.I). Compared to the O
₂
plasma, the IZO TFTs using N
₂
O plasma reactant during the G.I deposition show stable transfer characteristics. The IZO TFT using N
₂
O plasma with 150-W power during the G.I deposition shows the optimal positive/negative bias temperature stress (P/NBTS) results, with the threshold voltage (
$V_{\mathbf {TH}}$
) variations of 0.0 and −0.3 V, respectively.