薄膜電晶體適用於液晶面板上做為儲存電容開關，為了提高驅動電流與閘極控制力，選用high-κ材料做為介電層是未來的一個趨勢。鋁閘極的熱穩定性不佳，會限制其後製程回火溫度，而傳統多晶矽閘與high-κ材料之接面，向來存有極大缺陷密度。氮基金屬閘極氮化鉭(TaN)，可與氮化鋁(AlN)有良好的接面，而氮化鉭的熱穩定性，將使其後製程溫度較不受限制。

本論文以氮化鉭及氮化鋁分別做為金屬閘極與閘極介電層材料，進行電容及薄膜電晶體製作與電特性量測分析。於物性分析方面，係利用X光繞射分析(XRD)、化學分析電子儀(XPS)與歐傑電子分析儀(AES)等儀器分析氮化鉭與氮化鋁薄膜之組成、結構及成分分布等。實驗結果顯示，所得氮與鉭之原子比例為4：1，射頻功率180 W所獲得的金屬鍵結較強，結構則以(1,1,0)的相位為主，具有較佳的熱穩定性，配合TEM與實驗C-V特性分析，所得氮化鋁之κ值約為10。

我們利用氮化鉭/氮化鋁/p-Si MOS結構進行C-V特性和漏電流之量測，分析探討氮化鉭與氮化鋁之接面特性。同時，我門亦進行以氮化鉭/氮化鋁為閘極結構TFT之ID-VD和ID-VG等特性量測，所得TFT之Ion/Ioff約達六個數量級；另由ID-VG萃取出臨界電壓約為0.77 V、次臨界擺幅為1.6 V/decade。由實驗結果顯示，以氮化鉭為金屬閘極搭配氮化鋁閘極介電層的結構，適用於N型薄膜電晶體，深具TFT-LCD方面之應用潛力◦

Thin Film Transistors (TFTs) have been widely used as a switch of LCD pixels. To increase driving current and enhance gate control capability, there is a tendency towards using high-κ materials as gate insulator in the near future. Conventional TFTs usually use aluminium (Al) or poly-silicon (p-Si) as the gate material. However, the poor thermal stability of aluminium gate electrode limits thermal processing of the device, while defects at the interface between traditional poly-Si gate and dielectric degrade device performances.

In this thesis, tantalum nitride (TaN) and Aluminium Nitride (AlN) were employed to serve as gate metal and gate insulator for future TFT-LCD technology, respectively. Both these two films were sputtering deposited and thermally annealed. The physical properties and compositions of TaN film were analyzed using XRD, XPS, and AES. Experimental results shows that TaN films with relatively stronger binding energy could be obtained from a RF sputtering with a power of 180 W and the main phase of the film is (110).

MIS capacitances with TaN/AlN/p-Si structure and n-TFTs based on the same MOS structure were fabricated and characterized. C-V and leakage current for the MIS capacitances as well as IDS-VDS and IDS-VGS characteristics of TFTs were also measured and analyzed. According to C-V curves and TEM images, the high-κ AlN films prepared in this work were with a κ-value of 10 and a minimum EOT around 7 nm has been realized. Typical values of Ion/Ioff ratio, threshold voltage, and subthreshold swing (SS) obtained form the fabricated TFTs with TaN(300 nm)/AlN(18 nm)/poly-Si(100 nm) MIS structure were 106, 0.77 V, and 1.6 V/decade, respectively.

Though further studies are still required, our preliminary experimental results suggest that the sputtering deposited TaN and AlN films might work well for future TFTs.

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