The study of in-situ Hydrogen Plasma Treatment on IGZO active layer of TFTs with Atmospheric Pressure-PECVD

• Main Authors: Tan, Yu-Hsuan, 譚宇軒
• Other Authors: Chang, Kow-Ming
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/7w7w8f

碩士 === 國立交通大學 === 電子工程學系 電子研究所 === 104 === Conventional thin film transistor suffered from high threshold voltage, poor subthreshold swing, high operation voltage. These shortcomings make the traditional thin film transistor does not comply with the high-performance, high-resolution, low temperature and energy conservation nowadays. In the past few years, amorphous In-Ga-Zn-O (IGZO) thin film transistors had attracted attention that compared with the conventional a-Si:H TFTs, due to its better field-effect mobility (>10 cm2/V．S), larger Ion/Ioff ratio (>106), smaller subthreshold swing (SS) and better stability against electrical stress. On top of that, compared with low temperature ploy-Si (LTPS) TFTs, the a-IGZO TFT did not need high temperature process to recrystallize and activate the dopant. Furthermore, the a-IGZO TFTs had low process temperature, high transmittance that can be applied to fabricate the full transparent TFT on flexible substrate. To improve the performance of practical a-IGZO applications, most of the studies focused on adjusting process variables such as gas partial pressure, chemical components of target. In this investigation, we chose hydrogen plasma treatment which was a good way to improve Ion/off, subthreshold swing and field-effect mobility. As the scaling to Moore’s law, it is terrible that gate oxide is so thin (1.4nm) which caused an intolerable gate leakage due to direct tunneling current. We use the high-k material ZrO2 as our oxide to achieve the thinner EOT (4.05nm) and high on current but not degrade the leakage current. In this study, we used atmospheric-pressure PECVD (AP-PECVD) to deposit our IGZO active layer. With AP-PECVD, we could deposit IGZO thin film without vacuum system, thus, it could lower our cost, improved the throughput, and applied to large area manufacturing. Successfully, we fabricated a-IGZO TFT by plasma treatment with AP-PECVD. Without plasma treatment, it exhibited comparable mobility of 2.82 cm2/V•S, VT of 1.38 V, subthreshold swing of 116 mV/decade, Ion/Ioff is 3.4×106. With the post plasma treatment on IGZO active layer, the a-IGZO TFT exhibited higher mobility of 20.12 cm2/V•S, VT of 1.11 V, lower subthreshold swing of 93 mV/decade, higher Ion/Ioff of 5.34×107.