氮電漿處理高介電係數介電質二氧化鋯應用於大氣壓電漿輔助化學氣相沉積製備銦鎵鋅氧薄膜電晶體之研究

Abstract

非晶銦鎵鋅氧薄膜電晶體相對傳統非晶矽薄膜電晶體（a-Si:H TFTs）有較佳的電子遷移率(>10 cm2/V•S)，較大的開關電流比(>106)，較小的次臨界擺幅，且不需像低溫多晶矽薄膜電晶體(LTPS)得經過再結晶，活化摻雜等高溫的製程步驟，因此在近幾年得到了相當大的注目。而低製程溫度及高穿透率使得非晶銦鎵鋅氧薄膜電晶體可以用來製造透明且具可隢性的顯示器。 在這次的研究論文裡，我們採用了大氣壓電漿輔助化學氣相沉積(AP-PECVD)來沉積我們的銦鎵鋅氧主動層。藉由大氣壓電漿輔助化學氣相沉積的幫助，我們可以不需要真空腔體或真空系統便可以沉積我們的銦鎵鋅氧主動層，因此可以降低我們的成本,提高產率,並且利用再大面積的製造上。 隨著莫爾定律的演進，氧化層的厚度也越來越薄，當傳統二氧化矽厚氧化層度薄到1.4奈米時會導致不可避免得漏電流飆高，造成電性上的影響。因此我們採用高介電係數材料二氧化鋯來當我們的氧化層，藉此我們可以獲得較薄的等效氧化層厚度(4.05奈米)，以及較高的驅動電流，卻又不會造成漏電的上升。氮電漿處理可以調變二氧化鋯薄膜的物理及電特性。較好的二氧化鋯薄膜應用在我們的非晶銦鎵鋅氧薄膜電晶體上可以得到更好的電性。 我們成功的藉由大氣壓電漿輔助化學氣相沉積製作出以二氧化鋯當氧化層的非晶銦鎵鋅氧薄膜電晶體，它的電子遷移率有11.4 cm2/(V•S)，臨界電壓 0.05 伏特，次臨界擺幅 182 mV/decade，開關電流比 2.6×106。而採用經氮電漿處理過的二氧化鋯當氧化層的非晶銦鎵鋅氧薄膜電晶體表現出更佳的電性，它擁有更高的電子遷移率18.2 cm2/V•S，臨界電壓 0.1伏特，更小的次臨界擺幅 155 mV/decade，更高的開關電流比 1.49×107。

In the past three years, amorphous In-Ga-Zn-O (IGZO) thin film transistors have attracted attention that compared with the conventional a-Si:H TFTs, due to its better field-effect mobility (>10 cm2/V．S), larger Ion/Ioff ratio (>106), smaller subthreshold swing (SS) and better stability against electrical stress. Besides, compare with low temperature ploy-Si (LTPS) TFTs, the a-IGZO TFT do not need high temperature process to recrystallize and activate the dopant. Furthermore, the a-IGZO TFTs have low process temperature, high transmittance that can be applied to fabricate the full transparent TFT on flexible substrate. In this investigation, we used atmospheric-pressure PECVD (AP-PECVD) to deposit our IGZO active layer. With AP-PECVD, we could deposit IGZO thin film without vacuum system, thus, it could lower our cost, improved the throughput, and applied to large area manufacturing. As the scaling to Moore’s law, it is terrible that gate oxide is so thin (1.4nm) which caused an intolerable gate leakage due to direct tunneling current. We use the high- material ZrO2 as our oxide to achieve the thinner EOT (4.05nm) and high on current but not degrade the leakage current. Furthermore, the post N2 plasma treatment on ZrO2 oxide can modify the physical and electrical properties, such as RMS, leakage current, the formation of interfacial layer, et al. We could use the modified ZrO2 thin film which shows better electrical properties as the a-IGZO TFT oxide. Thus, the a-IGZO TFT will exhibits better electrical characteristics. Successfully, we fabricated a-IGZO TFT with AP-PECVD using ZrO2 high-k dielectric. It exhibits comparable mobility of 11.4 cm2/V•S, VT of 0.05 V, subthreshold swing of 182 mV/decade, Ion/Ioff is 2.6×106. With the post N2 plasma treatment on ZrO2 oxide, the a-IGZO TFT exhibits higher mobility of 18.2 cm2/V•S, VT of 0.1 V, lower subthreshold swing of 155 mV/decade, higher Ion/Ioff of 1.49×107.