Abstract
低製程溫度及低熱預算加上使用電子迴旋共振式化學氣相沉積的氮 化矽做閘極絕緣層,無攙雜多晶矽做通道層,攙雜多晶矽做接觸層之多 晶 矽薄膜電晶體已被研製.在這次實驗過程中,不需要對無攙雜多晶矽及 攙 雜多晶矽做高溫和長時間的再結晶. 本文主要在探討多晶矽薄膜的特 性 以及成長多晶矽薄膜之後再加上快速退火熱處理, 對低溫研製之多晶 矽 薄膜電晶體特性的影響.經由電流--電壓的電性曲線取得了載子移動 率, 臨界電壓及開關電流比等參數, 我們發現由成長本質多晶矽薄膜的參 數 中,提高氫稀釋的比率可以改善多晶矽薄膜電晶體的特性,得到載子移 動 率為5.5E-2 cm2/Vxsec,關/閉電流比為1E3,次臨界擺動為1 V/dec,和 臨 界電壓為2 V.另外,藉著快速退火熱處理的方法,亦可以改善多晶矽薄 膜 電晶體的特性,得到載子移動率為0.66 cm2/Vxsec,關/閉電流比約為 1E3, 次 臨界擺動為5.7 V/dec,和臨界電壓為10 V. 總之,在低製程溫度及低熱預算之下,用較高氫稀釋比率的多晶矽 薄 膜以及成長多晶矽薄膜後的快速退火熱處理, 皆可得到特性較佳的多 晶 矽薄膜以及成長多晶矽薄膜後的快速退火熱處理, 皆可得到較佳的多 晶 矽薄膜電晶體,因此在這次研究工作中,我們已經研發出一新方法來研 製 低製程溫度及低熱預算的多晶矽薄膜電晶體. Polycrystalline-silicon（poly-Si）thin film transistor（TFTs）at low processing temperature and low thermal budget have been fabricated using the silicon nitride film as the gate insulator ，undoped polycrystalline silicon film as the channel layer ， and in-situ doped n-type polycrystalline silicon film as the contact layer as-deposited by electron cyclotron resonance chemical vapor deposition（ECR-CVD）．In this process，long-term recrystallization in undoped poly-Si and n+ poly-Si films is not needed．Effects of active poly-Si properties，and RTA treatment for poly-Si TFTs on the electrical properties of low processing temperature and low thermal budget poly-Si TFTs have been investigated．By the current-voltage measurements，field-effect mobility，threshold voltage，subthreshold swing，and ON/OFF current ratio were extracted．The performance of poly-Si TFTs are improved as the hydrogen dilution ratio of undoped poly-Si films is increased．A field effect mobility of 0.52 ㎝2/V×se， ON/OFF current ratio of 1×103，subthreshold swing of 1.4 V/dec ，and threshold voltage of 5.5 V were obtained．In addition，We fabricated poly-Si TFTs with RTA treatment，poly-Si TFTs have better electrical characteristics than those without RTA treatment．A field effect mobility of 0.66 ㎝2/V×sec，ON/OFF current ratio ~1×103，subthreshold swing of 5.7 V/dec，and threshold voltage of 11 V were obtained． Under the low processing temperature and low thermal budget，using higher hydrogen dilution ratio in the undoped poly-Si films and RTA treatment for poly-Si TFTs can get the poly-Si TFTs with better electrical properties．In this work，therefore，we have demonstrated a new method to fabricate poly-Si TFTs．