非晶銦鎵鋅氧薄膜電晶體之製程效應及偏壓應力穩定度研究

Study of Process Effects and Bias Stress Stability on Amorphous Indium-Gallium-Zinc-Oxide Thin Film Transistor

羅世益(Shih-yi Lo)

指導教授 ： 冉曉雯 ； 蔡娟娟

國立交通大學/電機學院/光電工程系所/碩士(2010年)

https://doi.org/10.6842/NCTU.2010.00556

摘要

在本論文中呈現一個完整的實驗流程來驗證非晶銦-鎵-鋅-氧薄膜電晶體(a-IGZO TFT)的不穩定特性的原因，以及如何利用製程的處理來達到一個穩定的 a-IGZO TFT 元件，三個製程處理包括：成膜、後段退火以及保護層處理皆已完成開發及分析，在成膜方面，影響成膜的參數包括基板溫度、射頻功率、工作壓力和製程氣體比例調整的研究中，我們也証明了 a-IGZO 薄膜由導體至絕緣體之間的特性可經由製程參數來進而調整，在後段退火處理方面，我們發現元件特性可以經由退火處理使元件達到最佳的狀態，特性包括：電子遷移率~10cm2/(V-s)，次臨界擺幅~0.1V/dec. 以及開關比~108，元件在保護層處理後，我們驗證了元件的正向穩定度可經由保護層獲得改善，且在上保護層的元件，元件特性依然能保持且沒有任何劣化的情形發生。
我們也對元件在每次處理之後其正向及反向電壓下的穩定度進行分析，我 們也提供了這兩種電壓方向下不穩定機制的解釋，a-IGZO TFT 元件特性及穩定度在於每個處理下的演變也用來作為分析及比較，最終完成的高元件特性及高穩定度的電晶體是依序經由這三種處理所完成的，此元件在正向及反向的穩定度測試中，其時間常數各別為 860000 秒及 2140000 秒，總篇論文在 a-IGZO TFT穩定度提升的研究中提供了一個可行性的改善方向。

關鍵字

電晶體 ； 薄膜 ； 銦鎵鋅氧 ； 非晶

並列摘要

In this study, a complete experiment is performed to verify the origin of bias stress induced instability and a fabrication procedure is recommended to attain a stable amorphous In-Ga-Zn-O TFT (a-IGZO TFT). Three treatment phases, including as-deposited, post-annealing, passivated on amorphous Indium-Gallium-Zinc-Oxide thin film transistors (a-IGZO TFTs) were developed and investigated. In as-deposition phase, the influence of deposition parameters on a-IGZO TFTs like substrate temperature, RF-power, working pressure, and gases ratio, are investigated. We demonstrated the phases change from conductor to insulator of the a-IGZO film is tunable by modulating these parameters. In post-annealing phase, the optimized electric characteristic of a-IGZO TFT was attained with mobility ~10cm2/(V-s), sub-threshold swing ~0.1V/dec. , and on/off ratio ~108. In passivation phase, we demonstrated the positive stability of the device enhanced obviously with no degradation of electric performance.
The investment of stability in positive and negative bias stress was implemented for each treatment phase. We provided mechanisms of instability in a-IGZO TFT in each bias stress direction. The evolution of electric characteristics and stability of each treatment phase on device was also investigated. The final device, finished three phase treatments in order exhibited a high-performance and high-stability characteristic. The time constants of threshold voltage shift fitting model under positive and negative bias stress are 860000-sec. and 2140000-sec., respectively.
This thesis provided a usable direction to develop a feasible a-IGZO TFT device with acceptable stability.

並列關鍵字

transistor ； thin film ； igzo ； amorphous

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