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標題: | 可撓性P型氧化亞錫薄膜電晶體之電性與穩定性研究 Electrical Performance and Bias-Stress Stability of Flexible P-Type Tin Monoxide Thin-Film Transistors |
作者: | Jyun-Ci He 何鈞棋 |
指導教授: | 陳奕君(I-Chun Cheng) |
關鍵字: | 氧化亞錫,p型氧化亞錫薄膜電晶體,軟性電子元件,偏壓穩定性, tin monoxide,p-type SnO TFT,flexible electronics,gate-bias stress stability, |
出版年 : | 2015 |
學位: | 碩士 |
摘要: | 本實驗成功開發出製作於可撓性基板上之下閘極p型氧化亞錫薄膜電晶體,並且為首次探討機械應變對可撓性p型氧化亞錫薄膜電晶體之研究。首先,我們探討不同氧氣流量比例下,氧化亞錫之薄膜性質與電晶體特性。接著,我們對電晶體進行背通道層的封裝,並且研究其在彎曲情況下,包含受到張應力以及壓應力時,電晶體特性的改變。另外,也對電晶體進行彎曲疲勞測試,觀察經過多次的彎曲後,對於整體的電性上是否有任何變化。最後,我們研究電晶體在偏壓下的穩定性,分析在施加正負閘極偏壓後,試片在彎曲情況下,其穩定性的變化。
本研究採用金屬錫作為靶材,利用射頻磁控濺鍍系統在室溫下沉積氧化亞錫薄膜,接著對薄膜在空氣環境中進行225^。C、持溫30分鐘的退火,在濺鍍過程中通入不同比例的氧氣流量(3.6%~4.8%)以調變薄膜性質。以低掠角X光繞射分析薄膜的晶格結構,所沉積之氧化亞錫薄膜晶格方向以SnO(1 0 1)為主,隨著氧量的增加其結晶強度將逐漸增強。此外,在相同濺鍍條件下,觀察在玻璃基板上與軟性基板上之氧化亞錫薄膜的結晶優選方位並無明顯差異。 在電晶體電性的部分,場效載子遷移率隨著製程時氧氣流量比例,呈現先增後降的趨勢。經過封裝的電晶體可達到場效載子遷移率0.45 cm^2/V-s、臨界電壓1.93 V、次臨界擺幅2.79 V/dec、電流開關比1.5×10^4。在彎曲測試中,當氧化亞錫薄膜電晶體承受張應變(tensile strain)時,場效載子遷移率會下降,臨界電壓及次臨界擺幅則隨應力而增加;受到壓應變(compressive strain)時,各項特徵參數則無明顯變化。在疲勞測試中,隨著彎曲次數增加,場效載子遷移率逐漸降低,而臨界電壓則明顯提升,但在次臨界區無明顯變化。而在閘極偏壓穩定性測試中,臨界電壓偏移符合延展式指數關係式,由此推測電晶體不穩定性主要來自介電層與通道層界面或介電層本身電荷捕捉的影響,且在承受張應變下,此不穩定性更加顯著。 In this research, flexible p-type tin monoxide (SnO) thin-film transistors (TFTs) with an inverted-staggered bottom-gate structure were demonstrated on polyimide foil substrates. First, we investigated the effect of oxygen flow ratio (OFR) on the property of SnO thin films and the electrical performance of SnO TFTs. Next, we developed the back channel encapsulation of the SnO TFTs. The influence of mechanical strain, including tensile and compressive strains, on the performance of encapsulated flexible SnO TFTs and their bending fatigue performance were then investigated for the first time. Finally, the gate-bias stability of the flexible SnO TFTs under mechanical deformation was studied. P-type tin monoxide (SnO) thin films were deposited by reactive rf-sputtering using a metal tin target at room temperature, followed by a furnace annealing at 225^。C in air ambient. The thin film properties were modulated by varying the oxygen flow ratio (3.6%~4.8%) during the sputtering process. The grazing incidence X-ray diffraction analysis reveals that the preferred orientation of SnO thin films is (1 0 1). When the oxygen flow ratio increases, the crystallinity of the SnO thin film increases. Furthermore, there is no significant difference in the preferred orientation when the SnO thin film is deposited on a rigid glass or flexible polyimide foil substrate. For the SnO TFTs, the linear mobility increases first and then decreases as the oxygen flow ratio increases. The encapsulated SnO TFT exhibits a field-effect mobility of 0.45 cm^2V^-1s^-1, threshold voltage of 1.93 V, subthreshold swing of 2.79 V/dec, and on/off current ratio of 1.5×10^4. By applying a mechanical tensile strain (outward bending) to the TFT, a decrease in the field-effect mobility is observed. The threshold voltage and subthreshold swing also increase as the applied tensile strain increases. When a compressive strain is applied, no obvious change is observed in the TFT performance. In the bending fatigue test, the field-effect mobility decreases and the threshold voltage increases without significant change in the subthreshold swing as the number of bending cycle increases. In the gate-bias stress stability experiment, the evolution of the threshold voltage shift follows a stretch-exponential relation, suggesting the charge trapping at the interface or the gate dielectric is the dominant factor for the instability. The instability becomes more severe when a mechanical tensile strain is applied. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/52162 |
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顯示於系所單位: | 光電工程學研究所 |
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