Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/6127
標題: 氫化非晶氮化矽及非晶矽薄膜電晶體之研究
The Study of Hydrogenated Amorphous Silicon Nitride and Amorphous Thin Film Transistors
作者: 巫文豪
Hou, Wu Wen
關鍵字: amorphous
非晶矽
Thin Film Transistoer
amorphous silicon nitride
薄膜電晶體
氫化非晶氮化矽
出版社: 電機工程學系
摘要: 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.
URI: http://hdl.handle.net/11455/6127
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