發(fā)布時間：2018-01-23 22:07

  本文關(guān)鍵詞： 銦錫鋅氧化物 薄膜晶體管 射頻磁控濺射 工藝參數(shù) 有源層厚度　出處：《山東大學(xué)》2016年碩士論文　論文類型：學(xué)位論文

【摘要】：薄膜晶體管作為像素開關(guān)被廣泛應(yīng)用于液晶顯示器、有機發(fā)光二極管及電子紙等平板顯示和柔性顯示中。由于顯示器在視角、響應(yīng)速度、屏幕尺寸、對比度及功耗等方面的要求逐漸提高,對薄膜晶體管的要求也更高了。近7年來,ITZOTFT憑借遷移率高、亞閾值擺幅小等優(yōu)點成為研究的熱點,并被期待在顯示領(lǐng)域成為核心元件,但目前國內(nèi)對ITZO TFT的研究報道較少,制備工藝及工藝參數(shù)還在探索中。射頻磁控濺射技術(shù)制備的薄膜均勻、重復(fù)性好,還沒有發(fā)現(xiàn)用該技術(shù)系統(tǒng)研究ITZO TFT'性能的相關(guān)報道。本文采用此技術(shù)在室溫下硅襯底上制備以ITZO為有源層的TFT,研究了工藝參數(shù)及有源層厚度對器件電學(xué)性能和穩(wěn)定性的影響,其中,ITZO靶的靶材比例為IN2O3:SnO2:ZnO=88:10:2 wt%。(1)研究了濺射功率對ITZO TFT電學(xué)性能的影響,功率變化范圍為50-80W。實驗結(jié)果表明：功率太低時,不利于ITZO TFT電流開關(guān)比的提高；而功率太高則會造成TFT的關(guān)電流太大,器件失效。當(dāng)濺射功率為60 W時,ITZO TFT的關(guān)電流值最小為10-10A、電流開關(guān)比為105。(2)在壓強分別為0.4、0.6、0.8、1.0 Pa時制備了ITZO TFT,研究濺射氣壓對器件性能的影響。隨著氣壓的增大,ITZO TFT的遷移率逐漸降低、負(fù)向閾值電壓先減小后增大,這是由載流子濃度和界面缺陷密度兩方面因素共同決定的。0.6 Pa是制備ITZO TFT較為理想的沉積氣壓。(3)采用氧分壓分別為12%、17%、19%制備了ITZO TFT。隨著氧分壓的增大,TFT的閾值電壓由負(fù)值變?yōu)檎�、遷移率先增大后減小。當(dāng)氧分壓為17%時,器件的綜合電學(xué)特性最好：遷移率大小為6.28 cm2／Vs、電流開關(guān)比高于105、亞閾值擺幅僅為0.60 V/decade.(4)研究了ITZO TFT的電學(xué)性能在不同厚度有源層影響下的變化規(guī)律。采用最優(yōu)的工藝參數(shù)：濺射功率60 W、濺射氣壓0.6 Pa、氧分壓17%,ITZO厚度分別為16、25、36、45、55 nm。隨著厚度的增加,TFT的遷移率先上升后下降,而閾值電壓呈現(xiàn)出相反的變化趨勢；除有源層厚度為16 nm的TFT外,其它厚度對應(yīng)TFT的電流開關(guān)比均高于105、亞閾值擺幅都在0.8 V/decade以下。(5)對器件的穩(wěn)定性做了初步研究,研究對象是不同有源層厚度的ITZOTFT,條件是在大氣氛圍中靜置20天。通過測試電學(xué)特性發(fā)現(xiàn)：有源層為16 nm的器件輸出特性最差；36 nm對應(yīng)的器件閾值電壓漂移達(dá)到12.51 V；而55 nm的ITZO TFT閾值電壓漂移只有1.07 V,穩(wěn)定性較好。將ITZO TFT在60℃空氣氛圍中加熱360 s后發(fā)現(xiàn)：有源層厚度為45、55 nm的ITZO TFT的遷移率提高了3倍多,幾乎達(dá)到初始水平；閾值電壓略有增大；亞閾值擺幅變化不大,均在0.8 V/decade以下。由此得出：增加有源層厚度可以削弱空氣和水分對TFT造成的侵蝕、提高器件在空氣中的穩(wěn)定性；加熱可以有效地抑制空氣對器件造成的不良影響同時提升TFT在閾值電壓方面的性能。
[Abstract]:Thin film transistors are widely used as pixel switches in liquid crystal displays, organic light-emitting diodes, electronic paper and other flat panel display and flexible display, because of the display in the angle of view, response speed, screen size. The requirement of contrast and power consumption is increasing gradually, and the requirement of thin film transistor is also higher. In the last seven years, ITZOTFT has become a hot topic because of its high mobility and small sub-threshold swing. It is expected to become the core component in the field of display, but there are few reports on the research of ITZO TFT in China at present, and the preparation process and technological parameters are still under exploration. The thin films prepared by RF magnetron sputtering are uniform. Good reproducibility has not been found in the study of the performance of ITZO TFT'by using this technique. In this paper, TFT with ITZO as active layer was prepared on silicon substrate at room temperature. The effects of process parameters and active layer thickness on the electrical properties and stability of the devices are studied. The effect of sputtering power on the electrical properties of ITZO TFT was studied. The experimental results show that when the power is too low, the current switching ratio of ITZO TFT is unfavorable. If the power is too high, the switching current of TFT will be too large and the device will fail. When the sputtering power is 60W, the minimum off current value of ITZO TFT is 10-10A. ITZO TFT was prepared when the current switching ratio was 105. 2) and the voltage was 0. 4 ~ 0. 6 ~ 0. 8 ~ 0. 0 Pa, respectively. The effect of sputtering pressure on the device performance is studied. With the increase of pressure, the mobility of ITZO TFT decreases gradually, and the negative threshold voltage decreases first and then increases. It is determined by carrier concentration and interface defect density that 0.6Pa is the ideal deposition pressure for preparing ITZO TFT.) the oxygen partial pressure is 12%, respectively. With the increase of oxygen partial pressure, the threshold voltage of ITZO is changed from negative to positive, and the migration increases first and then decreases. When the oxygen partial pressure is 17, the threshold voltage of TFT is increased. The overall electrical properties of the device are the best: the mobility is 6.28 cm ~ 2 / V _ s and the current-switching ratio is higher than 105. The sub-threshold swing is only 0.60 V / decade. 4). The variation of electrical properties of ITZO TFT under the influence of different thickness active layers was studied. The optimal process parameter: sputtering power 60W was adopted. The thickness of ITZO in the sputtering pressure is 0.6 Pa, and the thickness of ITZO is 162525, 36, 4555 nm, respectively. With the increase of the thickness, the TFT increases first and then decreases. The threshold voltage showed the opposite trend. With the exception of TFT with active layer thickness of 16 nm, the current switching ratio of other thickness corresponding to TFT is higher than 105. The subthreshold swing is below 0.8 V / decade. The stability of the device is studied preliminarily. The object of study is ITZOTFT with different active layer thickness. The experimental results show that the output characteristics of the device with active layer of 16 nm are the worst. The threshold voltage drift of the device corresponding to 36 nm is 12.51 V. The threshold voltage shift of 55 nm ITZO TFT is only 1.07 V. When ITZO TFT was heated in air at60 鈩，

本文編號：1458351