The Study of LTPS-TFTs with CF4 plasma pre-treated poly-silicon and N2 plasma post-treated HfO2 Gate Dielectric Layer

• Main Authors: Huang, Bo-Wen, 黃柏文
• Other Authors: Chang, Kow-Ming
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/65163895817711614308

碩士 === 國立交通大學 === 電子研究所 === 100 === In recent years, high performance low-temperature polycrystalline-silicon thin-film transistors (LTPS-TFTs) have been attracted much attention due to the increasing applications in active matrix display (AMLCDs). However, the scaling to Moore’s law are limited to the lithography, the more minimum feature size as we need to pattern, the shorter wavelengths of light we must to achieve, so it is impossible to scale down forever. It is terrible that gate oxide is so thin (1.4 nm) which caused an intolerable gate leakage due to direct tunneling current. Therefore, high-k gate dielectric material has been extensively studied in recent year, which could effectively reduce leakage current and improve device performance. There are many high-k dielectric materials had been used before, hafnium oxide (HfO2) is considered one of the promising high-k gate material due to its high permittivity (25-30), wide energy bandgap and thermal stability with poly-Si. The HfO2 LTPS-TFTs were used as without treatment sample and combined with dual plasma treatment because of the combination of pre-deposition plasma fluorination and post-deposition plasma nitridation. We discussed not only the basic electrical characteristics but also reliability properties such as positive-bias stress instability (PBI), positive-bias temperature instability (PBTI), negative-bias stress instability (NBI) and hot carrier stress (HCS). No matter how the stress mechanism applies, the dual plasma treatment LTPS-TFTs exhibits a superior performance than without treatment. It might be that fluorine incorporation can improve the interface quality and nitrogen also can repair defects at bulk dielectric to decrease the leakage current.