熱退火條件之於IGZO金屬氧化物薄膜電晶體特性影響之研究

Abstract

在本文中,我們對低溫下沉積的a-IGZO薄膜電晶體的不穩定性進行了研究。在連續量測七次IDVG的電性後，發現此不穩定元件的Von會有很嚴重的偏移現象。這暗示了在低溫濺射的沉積過程中，主動層薄膜裡面原子之間的鍵結是不夠的完整的。因此，在通道與絕緣層的介面上產生了缺陷態。 另外，本文也討論了環境對於熱退火的影響。藉由改變熱退火時的氛圍，觀察a-IGZO 薄膜電晶體的電性分析。在量測時，觀察到a-IGZO 薄膜電晶體在真空環境熱退火與在大氣環境熱退火會有截然不同的現象。在真空環境底下熱退火後的元件會隨著退火溫度的升高呈現導通的現象。想反地，在大氣環境底下熱退火後的元件會隨著退火溫度的升高呈現絕緣的現象。本實驗藉由熱脫附質譜術(TDS)與X光光電子能譜(XPS)來探討此現象的機制。經過分析與討論後，確認氧原子會因為不同環境下熱退火的處理會有進入與跑出薄膜裡面的兩種行為。另外，此篇論文之研究，是與周政偉學長與陳蔚宗學長所共同進行開發的。

The stability of as-deposited a-IGZO TFTs was studied. The serious turn-on voltage shift under seven times sequent IDVG measurement of unstable as-deposited device was observed. It suggests that the atomic bonding of film was loose due to low temperature during sputter process. Hence, the defects were formed in the interface between channel and dielectric layer. By varying the post-annealing ambiance, it was observed that the transfer characteristic of a-IGZO TFTs annealed in vacuum based furnace and atmosphere based furnace were totally opposite. The device annealed in vacuum based went toward to conductive with increasing temperature. In the contrary, the device annealed in atmosphere based went toward to insulate with increasing. The mechanism was investigated by the thermal desorption spectrometry (TDS) and X-ray photoelectron spectroscopy (XPS). It was confirmed that the post-annealing could introduce oxygen into IGZO film or extract oxygen from IGZO film depending on the annealing ambiance. Besides, this work was studied with my senior classmates, Cheng-Wei Chou and Wei-Tsung Chen.