Low-temperature pulsed-PECVD ZnO thin-film transistors

We report high-quality ZnO thin films deposited at low temperature (200°C) by pulsed plasma-enhanced chemical vapor deposition (pulsed PECVD). Process byproducts are purged by weak oxidants N ₂O or CO ₂ to minimize parasitic CVD deposition, resulting in high-refractive-index thin films. Pulsed-PECVD-deposited ZnO thin-film transistors were fabricated on plasma-enhanced atomic layer deposition (PEALD) Al ₂O ₃ dielectric and have a field-effect mobility of 15 cm ²/V s, subthreshold slope of 370 mV/dec, threshold voltage of 6.6 V, and current on/off ratio of 10 ⁸. Thin-film transistors (TFTs) on thermal SiO ₂ dielectric have a field-effect mobility of 7.5 cm ²/V s and threshold voltage of 14 V. For these devices, performance may be limited by the interface between the ZnO and the dielectric.