Total-Ionizing-Dose Effects in IGZO Thin-Film Transistors With SiO2 Oxygen-Penetration Layers

Total-ionizing-dose (TID) effects are evaluated in top-gated IGZO thin-film transistors (TFTs) irradiated with different gate biases. Negative-bias irradiation leads to worst case degradation of TID response, primarily due to enhanced charge trapping in the SiO2 insulator that underlies the IGZO channel and serves as an oxygen-penetration layer during device processing. TID response comparisons with back-gated devices indicate that hydrogen also plays an important role in the observed degradation of top-gated devices. The source of this hydrogen is most likely SiN oxygen blocking layers. Comparisons with other display and alternative-channel MOS technologies illustrate that further optimization should enable the use of IGZO in future space applications.