近幾年來，降低溫度沈積介電質，以沒有損害到介電質的方式，已成為薄膜領域的主流。低溫沈積方式是相當重要的，如完成一薄膜電晶體於超薄、塑膠性基板上，只能予許溫度上升到100℃左右。在未來的顯示器裡，這樣的可撓曲基板可以取代玻璃基板，如此便可具有較低的成本、較低的耗電量、輕薄、可撓曲、可攜帶…等等優點。
現今標準的閘極介電質應用於非晶矽薄膜電晶體係以射頻電漿增強式化學氣相沈積法(rf-PECVD)沈積的氮化矽。然而，以rf-PECVD的製程溫度為300℃，對於可撓曲顯示器的製程溫度太高。另一方面，rf-PECVD所沈積之薄膜具有高達20 atom %的氫濃度，以及太低的介電強度。而低溫製程中，以電子迴旋共振式電漿輔助化學氣相沈積(ECR-PECVD)的氮化矽具有良好的材料特性及電性。ECR-CVD使用於低壓，具備一低電子和離子能，以及極高的游離能。因為ECR產生之電漿有非常的密集性，在離子撞擊時，有效率的減少非理想的氫鍵結濃度，使得沈積的溫度可以更低。
我們所得到的氮化矽薄膜在室溫沈積，並沒有作任何退火製程，其氫的鍵結很小。文獻中指出，氦氣在rf-PECVD製程中具有減小氫含量的作用。因此，在我們的ECR-CVD系統中，所用的氦氣當作silane的載入氣體。文獻中亦指出，rf-PECVD以氮氣取代氨作為製程氣體所沈積之氮化矽，其電性上具有較好的表現(高崩潰電場)。
在我們的研究中，改變silane的流量、針對不同的氮氣流量、以及對兩種不同的微波功率(microwave power)，研討其對沈積速率、薄膜組成、鍵結結構、以及電性(C-V, I-V measurement)方面的影響，找出最佳化的製程條件。其中以其電性作為我們研究的要點。

Decreasing the temperature at which dielectrics are deposited without causing any deterioration of the dielectrics properties has become a priority in the thin film research area. Low-temperature deposition is needed, for example, for producing thin film transistors (TFTs) on ultra-thin, plastic substrates that can withstand temperatures of up to 100℃. Such flexible substrates may replace the glass screens in future displays due to several advantages, e.q., lower cost, lower power consumption, lower weight, and better flexibility.

The standard gate dielectric nowadays for amorphous TFTs is silicon nitride deposited by radio-frequency plasma enhanced chemical vapor deposition (rf-PECVD). However, the processing temperature of rf-PECVD is 300℃, which is too high for flexible displays. Furthermore, these layers exhibit high hydrogen contents of up to 20 atom % and low dielectric strength. In contrast, electron cyclotron resonance (ECR) PECVD Si3N4 layers with good material and electrical properties have been successfully deposited in recent years, at much lower temperatures. ECR plasma operates at a low pressure, has a low electron and ion energy, and a high degree of ionization. Because of the dense characteristics of the ECR plasma, the deposition temperature can be lowered, while reducing the concentration of unwanted hydrogen bonds through ion bombardment.

Our aim is to obtain layers with low hydrogen bonds at room temperature, without any annealing process. Helium is known to efficiently eliminate hydrogen in rf-PECVD layers. Hence silane diluted in helium was employed as a gas precursor in our deposition system.

In this thesis, the influences of the silane flow, the nitrogen flow, and two different microwave power on deposition rate, film composition, and capacitance-voltage (C-V) and I-V measurements were investigated in order to find the optimal deposition conditions. We focused on the electrical characteristic.

Contents
Chinese AbstractⅠ

English AbstractⅡ

AcknowledgementⅢ

ContentsⅣ

Chapter 1. Introduction 1
1.1 Introduction of Dielectric : Silicon Nitride 1
1.2 Essential Material Considerations and Requirements for Silicon Nitride film 2
Reference 4
Chapter 2. Theory 5
2.1 The Plasma Characteristics and Film Formation Generated by the Electron Cyclotron Resonance Mechanism 5
2.1.1 Plasma Characterization 5
2.1.2 Formation of Silicon Nitride Film by ECR-CVD 8
2.2 The Growth of Amorphous Silicon Nitride Film 10
2.2.1 Deposition mechanism 10
2.2.2 Low temperature Silicon Nitride films deposition 11
2.3 Material Characteristic Analysis of Silicon Nitride 13
2.4 Capacitance –Voltage Characteristic of MIS Structure 21
2.4.1 Capacitance-Voltage Curves 21
2.4.2 Nitride Trapped Charge 26
2.5 Current –Voltage Characteristic of MIS Structure 27
2.5.1 Introduction 27
2.5.2 Fowler-Nordheim Tunneling 28
2-5-3 Direct Tunneling 30
Reference 31
Chapter 3. Experiments 35
3.1 Growth of Hydrogenated Silicon Nitride in ECR-PECVD System 35
3.2 Material Analysis of the SiNx:H Film 40
3.2.1 Deposition kinetics 40
3.2.2 Film composition 41
3.3 Electrical Measurement of the MIS Structure 42
Chapter 4. Results 43
4.1 Deposition Rate & Compositions of Silicon Nitride 43
4.2 Bonding Configuration 48
4.3 The C-V Characteristics of silicon nitride 50
4.4 The I-V Characteristics of silicon nitride 53
Reference 55
Chapter 5. Discussion and Conclusion 56

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