Investigation of Electrical Characteristic Degradation Mechanisms Caused by the Hot-Carrier and Self-Heating Effects in InGaZnO Thin Film Transistors

• Main Authors: Yu-te Chen, 陳聿德
• Other Authors: An-Kuo Chu
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/03898664940098275039

碩士 === 國立中山大學 === 光電工程學系研究所 === 101 === It is found that the metal-oxide semiconductor such as indium-gallium-zinc-oxide thin film transistor under the high current, high bias, and light illumination operation can cause electrical characteristic degradation. Especially, self-heating and hot-carrier effects are very important issues in practical TFT operation. In the study of self-heating effect, both the asymmetric degradation behavior and more positive Vt shift than that of PGBS are dominated by high gate- and drain-bias operation. Further, Vt shift decreases as the channel width decreases but increases as the channel length decreases. Besides, the channel current under dc-measurement is larger than that under ac-measurement. To investigate these abnormal phenomena, a series of experiments are carried out, such as dc SHS, ac SHS, varied-temperature tress, and varied-power stress, etc. Moreover, the degradation behavior of hot-carrier effect in via-contact type dual gate IGZO TFT with an etching stop layer is investigated in this study. The characteristic I-V and C-V curves under top/bottom gate bias are discussed. It is found that the hot-carrier effect in TFT with an etching stop layer is different from which without an ESL, and therefore it is inferred that the characteristics are strongly related to device structure, where the TFT with an ESL leads to top gate bias screening by the redundant source/drain electrodes. Accordingly, the various top gate capping lengths, various channel lengths, and varied drain electrode lengths experiment are performed to verify that the redundant source/drain electrodes in the device can affect device characteristics as well as the degradation behavior after HCS. Finally, in the investigation of illuminated dc and ac bias-stress in InGaZnO thin-film transistors, the effects of illuminated bias stress on characteristics are discussed. There is a hump at the off-state in Cgd curve, and Vt shifts in negative direction after illuminated stress. Moreover, ac/dc-bias stress under light illumination are performed to verify the proposed mechanism.