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標題: | 非晶相銦鎵鋅氧化物薄膜電晶體電特性及可靠度分析 Electrical Characterization and Reliability Analysis of Amorphous IGZO TFTs |
作者: | Chung-Sung Liao 廖重淞 |
指導教授: | 劉致為(Chee-Wee Liu) |
關鍵字: | 薄膜晶體電晶體,非晶相氧化銦鎵鋅,氧流量效應,三層通道結構,庫侖散射,表面粗糙度散射,量子侷限,能隙, Thin Film Transistor,Amorphous InGaZnO,Oxygen Flow Rate Effect,Triple Channel Structure,Coulomb Scattering,Surface Roughness Scattering,Quantum Confinement,Bandgap, |
出版年 : | 2018 |
學位: | 碩士 |
摘要: | 可靠度是背通道蝕刻單層通道結構非晶相氧化銦鎵鋅薄膜電晶體
的重要問題。以模擬作為基礎,臨界電壓總偏移值可以被分解為兩部分:(i)底部閘極絕緣體和(ii)頂部柵極絕緣體中被俘獲的電子所引起的臨界電壓偏移。對於背通道蝕刻單層通道結構非晶相氧化銦鎵鋅薄膜電晶體來說,背通道/頂部閘極絕緣體界面的品質非常差,但此介面卻是可靠度的關鍵。背通道中的載流子濃度也是一個重要問題,因為當背通道中有更多的電子,更多的電子陷入缺陷態以及閘極絕緣體,然後使臨界偏壓偏移更加嚴重。 沉積非晶相氧化銦鎵鋅通道層期間的高氧氣流量使得通道中的缺陷態更多,因此劣化了電晶體的電特性。沉積非晶相氧化銦鎵鋅通道層期間的高氧流量也使得閘極正偏壓測試的可靠度降低,但提高了閘極負偏壓照光應力測試的可靠度。因此無法同時兼得使用高氧流量沉積通道層的優點以及使用低氧流量沉積通道層的優點。 我們提出了三層通道結構的非晶相氧化銦鎵鋅薄膜電晶體。使用較高氧流量所成長的非晶相氧化銦鎵有較大的能隙。利用這個結果,使在電晶體通道裡製造一個量子阱,使電子被侷限於中間通道,因此使電子不會遭受太多的表面粗糙度散射和庫侖散射。此外,更薄的前通道厚度(10nm)能使場效電子遷移率更高(16cm2/V-s)。三層通道結構的非晶相氧化銦鎵鋅薄膜電晶體不僅具有更好的電特性,例如較小的次臨界擺幅(238mV/dec)和較小的遲滯效應(230mV),而且也具有比單層通道結構非晶相氧化銦鎵鋅薄膜電晶體更好的可靠度(包含正閘極偏壓測試以及負閘極偏壓照光測試)。量子阱侷電子於中間通道,以此較少電子可以到達通道/絕緣體界面,因此提高其可靠度。三通層道結構也可以改善上述的折衷現象。 Reliability is a significant issue of back-channel-etch single structure a-IGZO TFT. Base on simulation, value of VT total shift can be decoupled in two parts which are VT shift caused by trapped electrons in (i) bottom gate insulator and (ii) top gate insulator. For a back-channel-etch single structure a-IGZO TFT, quality of back channel/top gate insulator interface is very bad but and it is the key point of reliability. Carrier concentration at back channel is also an important issue, because more electrons at back channel, more electrons are trapped in to the defect states and gate insulator, and then make VT shift more severe. High oxygen flow rate during depositing a-IGZO channel makes more defect states in a-IGZO channel, and degrades the electrical characteristics of a-IGZO TFT. High oxygen flow rate during depositing a-IGZO also makes reliability of positive bias stress (PBS) test degrade, but improves reliability of negative bias illumination stress (NBIS) test. There is a trade-off between using high and low oxygen flow rate for depositing the channel layer. Triple channel structure a-IGZO TFT is proposed. High oxygen flow rate makes bandgap of a-IGZO enlarge. By using the result, making a quantum well in a-IGZO channel makes electron carriers mainly occupy in middle and let the carriers not suffer too much surface roughness scattering and coulomb scattering. Thinner the front channel thickness (10nm) makes higher field effect mobility (16cm2/V-s). Triple channel structure a-IGZO TFT can not only has better electrical characteristics such as smaller subthreshold slope (238mV/dec) and small hysteresis (230mV) but also has the better reliability (PBS&NBIS) than single channel structure a-IGZO TFT. Quantum well confines the electron carriers in middle channel, so electrons cannot go to the channel/insulator interface and improve the reliability. Triple channel structure can improve the trade-off as the mention above as well. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/77508 |
DOI: | 10.6342/NTU201801852 |
全文授權: | 未授權 |
顯示於系所單位: | 電子工程學研究所 |
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