Electrical Characteristics of a-IGZO TFTs With ${\hbox{SiO}}_{2}$ Gate Insulator Prepared by RF Sputtering

This study examined the electrical properties of a-IGZO thin-film transistors (TFTs) with a gate insulator of SiO
₂
, in which a more TFT-industry-compatible sputtering technique was used for all processing steps. Instead of plasma enhanced chemical vapor deposition, a room-temperature sputtered SiO
₂
gate insulator was used, which is more preferable for the simple and low cost process for oxide TFTs. The dielectric strength of the sputtered SiO
₂
film with an oxygen ratio of 6.25% was 6.3 MV/cm, which is sufficient for a gate insulator. The a-IGZO TFTs with the sputtered SiO
₂
gate insulators showed the optimal device parameters after post-annealing at 400°C for 1 hour in air: saturation field-effect mobility of 3.80 cm
²
/V·s, V
_th
of -2.84 V, on/off ratio of 1.43×10
⁵
, and S.S of 0.88 V/dec.