Thermal Analysis of Degradation in Ga₂O₃–In₂O₃–ZnO Thin-Film Transistors

Abstract

Degradation of Ga2O3–In2O3–ZnO (GIZO) thin-film transistors (TFTs), which are promising for driving circuits of next-generation displays, was studied. We found a degradation mode that was not observed in silicon TFTs. A parallel shift without any change of the transfer curve was observed under gate voltage stress. Judging from the bias voltage dependences we confirmed that the mode was mainly dominated by a vertical electric field. Thermal distribution was measured to analysis the degradation mechanism. Joule heating caused by drain current was observed; however, a marked acceleration of degradation by drain bias was not found. Therefore, we concluded that Joule heating did not accelerate degradation. Recovery of electrical properties independent of stress voltage were observed.

Low-temperature processable amorphous In-W-O thin-film transistors with high mobility and stability

“…26 Although our IWO device was not covered with a passivation layer, excellent electrical stability was obtained. According to the previous reports, the negative V th shift under bias stress is possibly caused by the applied voltages 27,28 and/or ambient water molecules, 29 the electrical stability of the present IWO films, however, became less sensitive with increasing W concentration. This is attributed to the high oxygen bond-dissociation energy of W (720 kJ/mol).…”

Thermal analysis of amorphous oxide thin-film transistor degraded by combination of joule heating and hot carrier effect

“…[7][8][9][10] Fujii et al have reported the self-heating effect of IGZO TFTs induced by Joule heating under voltage operation. 11 However, the result indicated in their paper has not been sufficient for explaining the degradation phenomenon of the oxide TFTs under electrical stress. Therefore, we have carefully investigated the relationship between the electrical degradation and thermal distribution of the ITZO TFTs by applying severe electrical stresses.…”

Influence of an anomalous dimension effect on thermal instability in amorphous-InGaZnO thin-film transistors

“…56 It is well known that the self-heating effect arises in silicon-oninsulator (SOI) MOSFETs and low-temperature-polycrystalline silicon (LTPS) TFTs because the surrounding oxide or other thermal insulating materials make it difficult to dissipate the heat generated in the active layer when high current flows through the channel, a situation quite similar to that found in the IGZO channel layer. 57 In addition, the thermal conductivity of IGZO is much lower than Si and is comparable to SiO 2 . Therefore, heat dissipation in IGZO TFTs is relatively more difficult than in Si-based TFTs.…”

“…Furthermore, because the temperature is highest at the center of the channel region and the heat dissipate to the surrounding materials along the channel width direction, larger channel widths make heat dissipation in the channel more difficult, again resulting in a more pronounced self-heating effect. 57,60 Moreover, the shorter the channel length, the higher drain current flowing through the channel, resulting in more heat generated in the channel. As a result, either a larger channel width or a shorter channel length combined with a higher operated drain bias will induce a more severe self-heating effect, resulting in more pronounce threshold voltage shift.…”