提升薄膜電晶體開關特性的技術是主動式矩陣顯示器技術發展的一重要趨勢，尤其在光致漏電方面，更是需要迫切解決的課題。在本研究中我們利用兩種方式來達成低光致漏電的非晶矽薄膜電晶體製作。我們首先提出一個新穎結構的非晶矽(a-Si:H)薄膜電晶體，可以抑制背光模組照射薄膜晶體所導致的漏電。我們在底匣極(bottom gate)及光屏蔽(light-shield)的結構中，沈積一層高含量磷摻雜的非晶矽薄膜覆蓋非晶矽主動層(a-Si island)的側壁。因此，可以有效地消除在非晶矽主動層側壁中，金屬源極/汲極電極與未摻雜非晶矽間形成之蕭特基接觸(Schottky contact)所造成的漏電路徑。此外，在背光源照射下，本研究所提出的新穎結構可以使光致漏電(photo leakage current)低於傳統結構達兩個級數之多。我們提出的結構所擁有的穩定特性，可以使顯示品質更好。另外在電性表現方面，新穎非晶矽薄膜電晶體表達出優越的有效電子遷移率。這樣的高性能表現，有極大的潛力應用於主動式矩陣液晶顯示器(AMLCD)及主動式矩陣有機發光二極體顯示器(AMOLED)技術中。
其次，我們提出另外一個方法來降低薄膜電晶體在關閉狀態(off-state)的光致漏電。我們選擇一種在矽半導體材料中具有深層缺陷能態(deep traps)特性的元素—銅，來當作傳導載子的復合中心(recombination center)。將做為比較組的電晶體元件浸泡在硫酸銅溶液中，使銅擴散進背通道(back channel)後，研究的結果顯示光致漏電流的值比浸泡前降低。雖然此方法造成電子有效遷移率些微的下降，但是降低的程度是在可以容忍的範圍之內。光-場效應(photo-field effect)可以初步解釋這個結果，因為在照光之下，較多的復合中心可以使得能帶彎曲減小(reduction of band bending)幅度較少。

There has been a tendency to improve the characteristics of switches in AMLCD (active matrix liquid-crystal display) technology. Particularly, the large photo-induce leakage current is an issue that need to be imminently solved. In this thesis, the amorphous silicon thin film transistors (a-Si:H TFTs) with low photo-induced leakage current will be proposed and studied.
A novel a-Si:H TFT structure has been demonstrated to suppress the leakage current under back-light illumination. The proposed TFT has an extra layer of heavily phosphorous-doped a-Si:H film capping on the side wall of a-Si:H island in the BCE light-shield structure. Thus, by excluding the effect of Schottky contacts between source/drain electrodes and undoped a-Si:H at the side edge of a-Si island, the leakage path can be effectively eliminated. Also, under the gate-side illumination, the proposed TFT structure shows a photo-induced leakage current as low as two orders of magnitudes, compared to the conventional a-Si:H TFT device. The superior characteristics of the proposed structure can potentially provide better visual quality for AMLCD products. Moreover, the novel a-Si TFT device exhibits higher effective carrier mobility than that of conventional one. For that reason, the high performance provides the potential of the proposed a-Si:H TFT to apply for AMLCD and AMOLED technology.
In addition, an alternative method has been proposed to suppress photo leakage current of a-Si TFT operated at off-state. We introduce a deep level trap center, copper, into Si film to act as recombination centers. After dipping conventional BCE TFTs into CuSO4 solution, copper will diffuse in back channel. Experimental results have shown the photo leakage current of devices is lower than that of a-Si TFT without the introduction of Cu. Although the mobility is decreased slightly, the degradation of mobility is still tolerable. The mechanism is mainly based on the photo-field effect that more recombination centers induce less reduction of band bending under illumination.

Chapter 1
[1.1] H. Yamamoto, H. Matsumaru, K. Shirahashi, M. Nakatani, A. Sasano, N. Konishi, K. Tsutsui, and T. Tsukada, IEDM Tech. Dig.,851 (1990)
[1.2] G. Kawachi, E. Kimura, Y. Wakui, N. Konishi, H. Yamamoto, Y. Matsukawa, and A. Sasano, IEEE Trans. Elec. Devices., 41, 1120(1994).
[1.3] D. B. Thomason, T. N. Jackson, IEEE ELECTRON DEVICE LETTERS, 18,8(1997).
[1.4] D. B. Thomason, T. N. Jackson, IEEE ELECTRON DEVICE LETTERS, 19, 4(1998).
[1.5] G. Kawachi, E. Kimura, Y. Wakui, N. Konishi, H. Yamamoto, Y. Matsukawa, A. Sasano, Electron Devices, IEEE Transactions on ., 41, 7(1994)
[1.6] R. M. A. Dawson, M. G. Kane, SID Tech. Dig., 372(2001)
[1.7] T. Tsujimura, Y. Kobayashi, K. Murayama, A. Tanaka, M. Morooka, E. Fukumoto, H. Fujimoto, J. Sekine, K. Kanoh, K. Takeda, K. Miwa, M. Asano, N. Ikeda, S. Kohara, and S. Ono, SID Tech. Dig.,6(2003)
[1.8] Y. He, R. Hattori, J. Kanicki, IEEE TRANSACTIONS ON ELECTRON DEVICE, 48, 7(2001).
[1.9] A. Nathan, D. Striakhilev, .Pervati, .K. akariya,.A.Kumar, K. S. Karim, A. Sazonov, Materials and Devices Technology as held at the 2003 MRS Spring Meeting.; 29(2003)
[1.10] M. Katayama, K. Nakazawa, Y. Kanemori, M. Katagami, Y. Kanatani, K. Yano, M. Hijikigawa, in Display Research Conference., 243(1991)
[1.11] I. Balberg, Y. Lubianiker, Phys. Rev. B , 8709(1993)
[1.12] T. Sunata et al., Proc. Soc. Inform. Display, vol. 27, pp. 229-234(1986)
[1.13] T. Sakai, M. Shimbo, M. Suzuki, T. Yamazaki, and R. Sakami, in Conf.
Rec. Int. Display Research Conf, 1985, pp. 30-31.
[1.14] N. Hirano, N. Ikeda, H. Yamaguchi, S. Nishida, Y. Hirai, and S. Kaneko,
IDRC ’94, International Display Research Conference, CA, p. 369(1994).
[1.15] M. Akiyama, H. Toeda, H. Ohtaguro, K. Suzuki, and H. Ito, in IEDM Tech. Dig., 268(1988)
[1.16] S. M. Sze, Physics of Semiconductor Devices, p. 402, Wiley, New York (1981).
[1.17] S. M. Sze, SEMICONDUCTOR DEVICES Physics and Technology 2nd EDITION, Ch.2, section.1, Wiley, New York, 2001
Chapter 2
[2.1] M. J. Powell, IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 36. NO. 12. DECEMBER 1989
[2.2] M. J. Powell. B. C. Easton, and D. H. Nicholls., J. Appl. Phys., vol. 53, pp. 5068-5078, 1982.
[2.3] M. Shur and M. Hack, J. Appl. Phys., vol. 53, pp. 3831-3842., 1984.
[2.4] M. Grunewald. P. Thomas, and D. Wurtz, Phys. Status Solidi (b), vol. 100, pp.139- 143, 1980.
[2.5] R. L. Weisfield and D. A. Anderson, Phil. Mug. B, vol. 44, pp. 83-93, 1981.
[2.6] T. Noda. Y. Ogawa, and T. Kurobe, Trans. IECE (Japan) E, vol. 64. pp. 134-140, 1981.
[2.7] F. Djamdji and P. G. LeComber. Phil. Mag. B, vol. 56, pp. 31-50, 1987.
[2.8] www.auo.com
[2.9] Y. Kuo, THIN FILM TRANSISTORS Material and Process, Vol.1, pp.7(2004)
[2.10] J. K. Yoon, Y. H. Jang, B. K. Kim, H. S. Choi, B. C. Ahn, and C. Lee, J. Non-Cryst. Solids 164-166, 747(1993)
[2.10] C. van Berkel and M. J. Powell, J. Appl. Phps., vol. 60, pp. 1521-1527(1986)
[2.11] S. M. Sze, SEMICONDUCTOR DEVICES Physics and Technology 2nd EDITION, Ch.7, section.1, Wiley, New York, 2001
[2.12] H. C. Lin, K. L. Yeh, R. G. Huang, C. Y. Lin, T. Y. Huang, IEEE Electron Device Letters, 2001
[2.13] K. L. Yeh, H. C. Lin, R. G. Huang, R. W. Tsai, T. Y. Huang, Jpn. J. Appl. Phys, 2002
[2.14] H. C. Lin, K. L. Yeh, T. Y. Huang, R. G. Huang, S. M. Sze, IEEE Transactions on Electron Devices, 2002
Chapter 4
[4.1] Y. E. Chen, J. H. Chen, and Y. H, Tai, ASID(1999)
[4.2] M. Katayama, K. Nakazawa, Y. Kanemori, M. Katagami, Y. Kanatani, K. Yano, M. Hijikigawa, Display Research Conference(1991), Conference Record of the 1991 International
[4.3] J. K. Yoon, Y. H. Jang, B. K. Kim, H. S. Choi, B. C. Ahn, and C. Lee, J. Non-Cryst. Solids, vol. 164–166, pp. 747–750(1993)
[4.4] S. Luana, G.W. Neudeck, Journal of Applied Physics., 72, 766(1992).
[4.5] C. Y. Chen, J. Kanicki, Solid-State Electronics., 42, 705(1998)
[4.6] B. Popescu, M. Hundhausen, and L. Ley, Journal of Non-Crystalline Solids., 283,155(2001)
[4.7] J. Kanicki, F. R. Libsch, J. Griffith, and R. Polastre, Journal of Applied Physics., 69, 2339(1991)
[4.8] S. M. GadelRab, S. G. Chamberlain, IEEE Trans. Electron Devices, Vol.41, No.3, March(1994)
[4.9] S. M. GadelRab, S. G. Chamberlain, IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 45, NO. 2, FEBRUARY(1998)
[4.10] R. A. Street and M. J. Thompson, Appl. Phys. Lett.. vol. 45, pp. 769-771(1984)
[4.11] W. E. Spear, J. Non-Cryst. Solids 59/60, 1(1983)
[4.12] K. S. Lee, J. H. Choi, S. K. Kim, H. B. Jeon, J. Jang, Applied Physics Letters, Volume 69, Issue 16, October 14, pp.2403-2405(1996)