Study on Improving the Stability of Amorphous Indium Zinc Tin Oxide Semiconductor Thin Film Transistor with Gallium Doped

• Main Authors: Chang, Chu-Chung, 張駒中
• Other Authors: Shieh, Han-Ping
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/52469514939997171580

碩士 === 國立交通大學 === 光電工程研究所 === 104 === In this thesis, a promising material, called amorphous InZnSnO (a-IZTO), is investigated for achieving the high mobility oxide thin-film transistors (TFTs) for next generation display. Many researches have reported that a-IZTO with high carrier concentration and high etching resistance suffers from the issue of stability under gate-bias stress. Compared to a-IGZO, a-IZTO is very suitable for back channel etching (BCE) process due to its high etching selectivity to electrodes in acid solution. There are some widely known methods for improving the stability of TFTs, such as post-annealing treatment and the post passivation deposition. We proposed the improvement of TFT stability by doping a small amount of Ga into a-IZTO. Ga3+ ions can suppress the carrier generation and the reduction of electron density is attributed to the stronger Ga-O (353.5 KJ/mol) bond strength compared with In-O (320.1 KJ/mol) and Zn-O (348.0 KJ/mol) bonds. Hence, the stability can be improved by doping Ga into the channel layer of a-IZTO TFTs. The oxide TFT with BCE structure is hopeful to be realized by using a-IZTO with and without Ga doping in the channel layer. We investigated the characteristics of a-IZTO and a-G:IZTO and the degradation of a-IZTO and a-G:IZTO fabricated by BCE process. Finally, we optimized the deposition condition of a-IZTO and a-G:IZTO. The value of the mobility, threshold voltage (Vth) and subthreshold swing (S.S.) were 31.29 cm2/V．s, -4.8 V and 0.4 for a-IZTO and 24.34 cm2/V．s, -1.8 V and 0.4 for a-G:IZTO, respectively. Furthermore, for BCE type devices, the value of the mobility, Vth and S.S. were 34.42 cm2/V．s, -5.8 V and 0.5 for a-IZTO and 26.08 cm2/V．s, -2.8 V and 0.5 for a-G:IZTO, respectively.