臺灣博碩士論文加值系統

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

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