本計劃探討以脈波調變電漿在氫氣稀釋下改變SiH4/NH3比例、總流量、及RF峰值功率等不同的製程條件對沈積a-SiNx:H薄膜特性的影響，藉以找出最佳條件的a-SiNx:H薄膜以製作氫化非晶矽薄膜電晶體。
SiH4/NH3比例、總流量、脈波開關比、RF峰值功率、氫氣稀釋比、反應壓力及基底溫度的設定範圍分別為1/3.75至1/15、220 sccm至266 sccm、25ms/500ms、400 W、50%、0.25 torr、以及275℃。
A-SiNx:H薄膜的特性分別以傅立葉轉換紅外線光譜儀(FTIR) 、N&K analyzer測量薄膜鍵結結構、厚度、折射率及光學能隙並製作Al/a-SiNx:H/N-type Si wafer/Al的MIS結構進行I-V及C-V的量測。
不同的SiH4/NH3比例，對a-SiNx:H薄膜中N/Si的比例有很大的影響，富氮態a-SiNx:H薄膜的電性如電阻值、崩潰電場（breakdown field）和接面狀態密度（interface state density Dit）都比富矽態a-SiNx:H來的優異。NH3/SiH4的比例增加時，使得薄膜成為富氮態（N-rich），折射率會下降，缺陷密度減少[1]，在接面處會減少電荷被捕捉（charge trapping）。
影響a-SiNx:H薄膜特性比的主要製程參數有三個，第一是SiH4/NH3流量比例，其次是射頻峰值功率，第三是氫稀釋比。不同的SiH4/NH3流量比會使a-SiNx:H薄膜產生不同的折射率，折射率影響薄膜的N-H鍵跟Si-H鍵的比例，當折射率越小，N-H鍵比Si-H鍵的比例會越大，代表薄膜的含N量較多，a-SiNx:H薄膜內的N/Si比大於1.33時，薄膜是屬於富氮態(Nitrogen Rich)，此時薄膜在電性方面會最好，漏電流最小。經過多次的實驗，得到下列對沉積a-SiNx:H薄膜最佳的製程參數，高的SiH4/NH3比例(1/15)，較長的Pulse-off time (23.33ms)，較低的功率(100W)，及50％氫稀釋下，所沈積的H2稀釋a-SiNx:H薄膜，折射率為1.46，具有最小的漏電流1.97×10-9 A/cm2(電場強度 1MV/cm條件下)、最大的介電值7.93、崩潰電場為6.96 MV/cm(電流密度J = 1μA/cm2條件下)、以及光學能隙為5.46eV。
以條件為NH3 105sccm，SiH4 7sccm，H2 112sccm，pulse-on time 10ms，pulse-off time 23.33ms，射頻峰值功率100W以及基板溫度275℃的氫化非晶氮化矽閘極介電層，利用CHP結構製作出TFT的元件特性為Ion/Ioff的比值達3.48×106，VT=3.01V，遷移率為0.86cm2/V-s。

The major application of hydrogenated amorphous silicon nitride (a-SiNx:H) film is gate dielectric material and passivation layer for thin film transistors (TFTs). A good quality a-SiNx:H film has those characteristics including low leakage current, low hydrogen content, high breakdown voltage, high dielectric constant and lower interface trapping density. Because the properties of a-SiNx:H film effects the performances of TFT.
Pulse-wave modulation RF plasma with changing frequency and duty cycle can alternate the radicals generated in the plasma. It is excepted that the N/Si ratio in a-SiNx:H can be adjusted precisely and the bonding quality of the a-SiNx:H can be modified by this unique technology.
The range of SiH4/NH3 ratio, total flow, pulse-on time/pulse-off time, RF peak power, and hydrogen dilution was set as 1/3.75 to 1/15, 220cssm to 266sccm, 25ms/500ms, 100W to 400W, 50%.
A-SiNx:H can be characterized with FTIR and N&K analyzer to analysis its characteristics, such as bonding structure, hydrogen content, thickness, refractive index, and optical energy gap. The C-V and I-V measurements were made with MIS Al/a-SiNx:H /N-type Si wafer/Al structure. The electrical, optical, and material properties of the a-SiNx:H films was discussed to find out influence of the different deposition conditions and the relation of those properties. The modification of the quality of the a-SiNx:H films using pulse-wave modulation RF plasma will be improved.
The major deposition conditions to influence the characteristics of a-SiNx:H films are NH3/SiH4 ratio, RF power, and hydrogen dilution ratio. The a-SiNx:H films deposited using higher NH3/SiH4 ratio (1/15), higher pulse-on time (23.33ms), lower RF peak power (100 W), and 50％ hydrogen dilution has the smallest leakage current density of 1.97×10-9 A/cm2(at 1 MV/cm)、the largest dielectric constant of 7.93, refractive index of 1.460, breakdown filed of 6.96 MV/cm (at J = 1μA/cm2), and energy bandgap of 5.46 eV。
A-Si:H TFT devices are fabricated using Channel-Passivated(CHP) structures. In CHP structure, the increasing of leakage current in the a-Si:H activation layer can be reduced due to the a-Si:H film passivated by the upper a-SiNx:H layer. The best a-Si:H TFT device in this study has the characteristics of Ion/Ioff = 2.48×106, threshold voltage VT = 3.01V, and field-effect mobility μ = 0.86 cm2/V-s.

第一章 簡介 1
1.1 應用於氫化非晶矽薄膜電晶體的氫化非晶氮化矽 1
1.2 脈波式調變電漿對薄膜特性的影響 2
1.3 氫氣稀釋對氫化非晶氮化矽薄膜特性的影響 3
1.4 折射率對a-SiNx:H薄膜特性的影響 4
1.5 氫化非晶矽薄膜電晶體的製程 4
1.6 研究方法 5
1.7 論文架構 6
第二章 脈波調變電漿製作氫化非晶氮化矽薄膜及其分析 7
2-1 氫化非晶氮化矽薄膜的成長 7
2-1-1 基材的選擇與清洗 8
2-1-1-1基材的選擇 8
2-1-1-2 試片清洗 8
2-1-2 實驗設計 9
2-1-3 氫化非晶氮化矽電容製作 11
2-2儀器測量原理與分析方法 11
2-2-1 N&K analyzer 11
2-2-2 FTIR 12
2-2-3 C-V量測 14
2-2-4 I-V量測 14
2-3 氫化非晶氮化矽薄膜特性分析 14
第三章 氫化非晶矽薄膜電晶體元件製作 20
3-1 氫化非晶矽薄膜電晶體的電流電壓特性 20
3-2 氫化非晶矽薄膜電晶體的電性量測 20
3-3 氫化非晶矽薄膜電晶體的製作 22
3-3-1微影 22
3-3-2蝕刻 25
3-3-3元件製程 26
第四章 結論 29
參考資料 32

[1] M.J. Powell, “Amorphous silicon-nitride thin-film transistors”, Appl. Phys. Letter, Vol 38, p794, 1981
[2] W.M. Armoldbik, “Dynamic behavior of hydrogen in silicon nitride and oxynitride films made by low-pressure chemical vapor deposition”, Phys. Rev. B Vol.48, p5444, 1993
[3] Yue Kuo, “Plasma enhanced chemical vapor deposited silicon nitride as a gate dielectric film for amorphous silicon thin film transistors — a critical review,” Vacuum vol.51 No.4 pp.741-745, 1998
[4] Stanley Wolf Ph.D., Silicon Processing for VLSI, 1986.
[5] M.C. Hugon, “Electrical properties of metal- insulator-semiconductor structures with silicon nitride dielectric deposited by low temperature plasma enhanced chemical vapor deposition distributed electron cyclotron deposition distributed electron resonance” J. Vac. Sci. Technol. A15(6), p3143, 1997
[6] Yue Kuo, “Etch mechanism in the low refractive index silicon nitride plasma-enhanced chemical vapor deposition process”, Appl. Phys. Lett. Vol. 63, no. 2, p144, 1993
[7] Takahiro Makino and Masahiko Maeda, “Bonds and Defects in Plasma-Deposited Silicon Nitride Using SiH4-NH3-Ar Mixture,” Japanese Journal of Applied Physics, Vol. 25, No. 9, September, 1986, pp. 1300-1306.
[8] Yue Kuo ,”PECVD Silicon Nitride as a Gate dielectric for Amorphous Silicon Thin Film Transistor Process and Device Performance,” J. Electrochemical Society, Vol.142, No. 1,p186-190, 1995
[9] Naftali Lustig and Jerzy Kanicki, “Gate dielectric and contact effects in hydrogenated amorphous silicon-nitride thin film transistors”, J. Appl. Phys. Vol.65, no.10, p.3951, 1989.
[10] W.L. Warren, “Energy level of the nitrigen dangling bond in amorphous silicon nitride”, Appl. Phys. Lett. Vol59, p1699, 1991
[11] G. N. Parsons, J. H. Souk, and J. Batey, “Low hydrogen content stoichiometric silicon nitride films deposited by plasma-enhanced chemical vapor deposition”, J. Appl. Phys. 70(3), p1553-1560, 1991
[12] H. Dun, “Mechanisms of Plasma-Enhanced Silicon Nitride Deposited Using SiH4/N2 Mixture”, J. Electrochem. Soc. Vol 128, p1555, 1981
[13] C. H. Ling, C. Y. Kwok and K. Prasad, “Silicon Nitride Films Prepared by Plasma-Enhanced Chemical Vapor Deposition (PECVD) of SiH4/NH3/N2 Mixture: Some Physical Properties,” Japanese Journal of Applied Physics, Vol. 25, No. 10, October, 1986, pp. 1490-1494.
[14] Yutaka Misawa and Hideyuki Yagi, “Electrical Conduction of Silicon Nitride Films Deposited by SiH4-NH3 Reaction,” Japanese Journal of Applied Physics, Vol. 15, No. 6, June, 1976.
[15] Shin Yokoyama, Masataka Hirose and Yukio Osaka, “Optical Emission Spectroscopy of the SiH4-NH3-H2 Plasma During the Growth of Silicon Nitride,” Japanese Journal of Applied Physics, Vol.20, N0. 2, February, 1981 pp. L117-L120.
[16] C.I. Ukah, R. Meh, and S. Zukotynski, “ Deposition of silicon nitride by glow-discharge decomposition of silane-nitrogen mixtures in a saddle-filed plasma”, Can. J. Phys. Vol. 69, p185-191, 1991
[17] 鄭本誠，”PECVD系統建立及測試研究”，中興大學物理系碩士論文，1995
[18] Darren Murley et al., ”The effect of hydrogen dilution on the aminosilane plasma regime used to deposit nitrogen-rich amorphous silicon nitride”, J. non-cryst. Solids., Vol.198-200, p.1058, 1996.
[19] R.E. Rocheleau and Z. Zhang, “Densification of plasma deposited silicon nitride films by hydrogen dilution”, Thin Solid Films, Vol.220, p73, 1992
[20] F. Giorgis, “Optical, structure and electrical properties of device-quality hydrogenated amorphous silicon-nitrogen films deposited by plasma-enhanced chemical vapor deposition”, Philosopical Magazine B, Vol.77, No.4, p925-944, 1998
[21] S. Haseagawa, “Effect of active hydrogen on the stress relaxation of amorphous SiNx:H films ”, J. Appl. Phys. Vol 75(3), p1493, 1994
[22] A. Matsuda and K. Tanaka “Investigation of the growth kinetics of glow-discharge hydrogenated amorphous silicon using a radical separation technique” J. Appl. Phys. Vol. 60, pp. 2351, 1986.
[23] Y. Watanabe, M. Shiratani, Y. Kubo, I. Ogawa, and S. Ogi “Effects of low-frequency modulation on rf discharge chemical vapor deposition” Appl. Phys. Lett. Vol. 53, No.14, pp. 1263-1265, 1988
[24] Y. L. Jiang, “The property of PECVD SiNx:H films influenced by helium dilution and pulse RF power”, IEDMS, 1998.
[25] P. G. LeComber, W.E. Spear, and A. Ghaith, “Amorphous Silicon Field-Effect Device and Possible Application,” Electronics. Lett., Vol.15, P.179-181,1979
[26] Martin J. Powell, “The Physics of Amorphous-Silicon Thin Film Transistors,” IEEE Transactions on Electron Devices, Vol. 36, No. 12, pp. 2753-2763, December 1989.
[27] R. A. Street and M.J. Thompson, ”Electronic States at the Hydrogenated Amorphous Silicon / Silicon Nitride Interface,“ Appl. Phys. Lett., Vol. 45, 1984, p.769.
[28] K. Hiranaka, T. Yoshimura and T. Yamaguchi, “Effects of Deposition Sequence on Amorphous Silicon Thin Film Transistors,” Jpn. J. appl. Phys. 28, 2197(1989).
[29] H. Uchida, K. Takechi, S. Nishida and S. Kaneko, “High-Mobility and High-Stability a-Si:H Thin Film Transistors with Smooth SiNx/a-Si Interface”, Jpn. J. Appl. Phys. 30, 3691(1991)
[30] Tina J. Cotler and Jonathan Chapple-Sokol, “High Quality Plasma-Enhanced Vapor Deposition Silicon Nitride,” J. Electrochemcial Society, Vol.140, No.7, p207 1-2075, 1993
[31] 陳慧穎，”氫化非晶氮化矽及氫化非晶矽薄膜電晶體之研究”，中興大學碩士論文，2000
[32] W. A. Lanford and M. J. Rand, “The hydrogen content of plasma-deposited silicon nitride”, J. Appl. Phys. 49(4), p2473-2477, 1978