Effects of Composition on Electrical Properties of Amorphous In-Ga-Zn-O Films Deposited Using Atmospheric Pressure Plasma Jet and Post Laser Annealing

• Main Authors: Chen, Chien-Yuan, 陳健源
• Other Authors: Chang, Kow-Ming
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/25393871774700912508

碩士 === 國立交通大學 === 電子工程學系 電子研究所 === 102 === Silicon dioxide (SiO2) has been gate dielectric because of its physical and electrical properties on silicon substrate. But gate leakage current becomes higher when shrinking of the gate length and gate dielectric thickness. Using high dielectric constant material for gate dielectric instead of SiO2 will solve the problem of the gate dielectric thickness. The oxide-based thin film transistors have good electrical properties and high transparency. Amorphous indium gallium zinc oxide (a-IGZO) has advantages of relatively high electron mobility and good chemical stability. In this thesis, new process technology is developed to deposit IGZO films. Atmospheric pressure plasma jet (APPJ) is proposed to fabricate IGZO thin film transistors. Also, water-based metal salt solution, which is an eco-friendly precursor, is adopted, and the thin film can be deposited in atmospheric environment. First, HfO2 and ZrO2 were deposited to fabricate capacitor and IGZO TFTs. According to the experience, we discover that the annealing temperature 500°C has the best condition because of higher capacitance and lower leakage current. Then we fabricated TFTs using IGZO as active channel layer. Many approaches have been studied to improve electrical performance. The channel composition of the IGZO has a large impact on device. The atomic mole ratio of In:Ga:Zn=1:1:1,1:1:2, and 3:1:2 were used as channel layer. The atomic mole ratio of In:Ga:Zn=1:1:2 exhibit a excellent electrical performance. The good electrical characteristics were achieved, including a VT of 0.628V, a subthreshold swing (SS) of 0.365 V/dec, a mobility of 19.8 cm2/V-s and a large Ion/Ioff ratio of 7.34x106. Finally, we investigate the effect of laser annealing on the IGZO TFTs. Because laser annealing can raise the temperature for a short period at a precise position, and can reduce the charge trapping in the gate insulator or the channel/insulator interface. The results show the leakage current of TFTs were all decreased. The molar ratio of In:Ga:Zn=1:1:2 has the best electrical performance with high mobility of 14.36 cm2/V-s, a threshold voltage of 0.16, subthreshold swing (SS) of 0.286 V/dec, and an on/off current ratio of 6.34×107.