臺灣博碩士論文加值系統

論文摘要

本研究是將Ti/Si及TiN/Ti/Si系統的試片進行升溫速率為每分鐘5℃的真空退火處理，在退火的同時，藉由臨場(In situ)曲率量測系統的量測，將可分析出試片在升溫過程應力變化的情形。此外，退火後的試片亦會進行X-光繞射儀(XRD)、四點探針(Four-Point Probe)、歐傑電子能譜儀(AES)及穿透式電子顯微鏡(TEM)的量測分析。因此，不同退火溫度所對應到的薄膜應力狀態、生成的相、電性、及微觀結構等將被解析出來，進而研究TiN覆蓋層對於Ti/Si系統的影響。

實驗結果發現，在退火溫度300~500℃之間，氧原子隨退火溫度升高而明顯的擴散進入Ti/Si系統中的Ti層，進而使得Ti晶格擴張，其對應於XRD的結果，可以看見Ti的峰值隨退火溫度的升高而往低角度偏移。而氧擴散進入Ti層的行為，使得薄膜受到一個往壓力方向的應力，片電阻亦因Ti層中氧的涵量提高而增加。然而，當覆蓋一層TiN後，氧的擴散受到了阻礙，Ti層中氧的涵量減少，因此片電阻隨退火溫度升高而增加的情形不再如Ti/Si系統明顯，而應力往壓應力方向的趨勢也不復見。

不同厚度的TiN覆蓋層對系統的影響亦受到研究，結果顯示相的轉變溫度不因改變TiN的厚度而有明顯的差異。然而，在低溫時(~300℃)可以發現矽原子在TiN較厚的試片中有較明顯的擴散行為發生，分析其原因，可能是不同厚度的TiN覆蓋層，使得試片內的應力狀態及涵氧程度有所不同，進而影響了矽原子的擴散。

Abstract

Ti/Si and TiN/Ti/Si structures were annealed in vacuum to observe the reaction sequence. The stress of the film was determined in situ by measuring the curvature of the sample during the isochronal annealing process. The phases of the film after annealing process were identified using XRD, sheet resistance measurements, AES, and TEM. A clear correlation was found between the evolution of stress and the phase formation sequence.

From the XRD data, we can find that the (002) peak of Ti shifts to low angle at 300~500℃ in the Ti/Si system. It is due to the oxygen-induced lattice expansion. The content of oxygen increases as the annealing temperatures increase, and this process let the sheet resistance increase and the stress become more compressive. For the TiN/Ti/Si systems, the TiN capped layer prevents the compressive stress developed at 300~500oC by retarding the oxygen incorporation into the Ti film.

Samples with different TiN thickness were also compared after annealed to the same temperature. At low temperature, the diffusion of Si at the Ti-Si interface is easier in the system with thicker TiN capped layer. It might relate to the situation of oxygen incorporation into the Ti film or the stress state at the Ti/Si interface. However, the temperatures at which phases start to transform are affected slightly by the thickness of TiN capped layer.

Contents

Abstract…………………………………………………………………I
Acknowledgement………………………………………………………IV
Contents…………………………………………………………………V
List of Figures……………………………………………………VIII
List of Tables…………………………………………………………XI

Chapter 1 Introduction………………………………………………1
1-1 Overview …………………………………………………………1
1-2 Silicide Applications……………………………………………1
1-3 Ti-Si system………………………………………………………3
1-4 TiN Thin Film Applications……………………………………5
1-5 Stress in Thin Film and Theory of Curvature Measurement…………………………………………………………6
1-5-1 Origin of Stress in Thin Film……………………………6
1-5-2 Effects of Stress in Thin Film……………………………8
1-5-3 Stress Measurement……………………………………………8
1-5-4 Laser Scanning Technique……………………………………9
1-5-5 Stoney’s Equation…………………………………………10
1-5-6 In Situ Curvature Measurement……………………………11
1-6 The Motivation of study………………………………………12

Chapter 2 Experimental and Analysis Technique……………14
2-1 Experimental Flowing Chart……………………………………14
2-2 Sample Preparation………………………………………………15
2-2-1 Wafer Cleaning………………………………………………15
2-2-2 Thin Metal Film Deposition…………………………………16
2-2-3 Sample Preparation for In Situ Curvature Measurement……………………………………………………17
2-2-4 Sample Preparation for Transmission Electron Microscope Observation………………………………………………18
2-3 Analysis Instrument……………………………………………19
2-3-1 In Situ Curvature Measurement System…………………19
2-3-1-1 Optics System……………………………………………20
2-3-1-2 Calibration Procedure…………………………………21
2-3-1-3 Vacuum Annealing System………………………………22
2-3-2 X-Ray Diffraction……………………………………………23
2-3-3 Four-Point Probe………………………………………………24
2-3-4 Auger Electron Spectrometer………………………………25
2-3-5 Transmission Electron Microscopy…………………………27

Chapter 3 Results and Discussion…………………………………29
3-1 As-deposited Samples……………………………………………29
3-2 Ti/Si System………………………………………………………32
3-2-1 In Situ Curvature Measurement of Ti/Si…………………33
3-2-2 XRD of Ti/Si…………………………………………………36
3-2-3 Four-Point Probe of Ti/Si…………………………………40
3-2-4 Stress Evolution of Ti/Si with AES and TEM Results………………………………………………………41
3-2-5 Effect of Oxygen………………………………………………46
3-3 TiN/Ti/Si System…………………………………………………47
3-3-1 Comparison Between TiN/Ti/Si and Ti/Si…………………47
3-3-1-1 In Situ Curvature………………………………………47
3-3-1-2 XRD and Four-Point Probe………………………………51
3-3-1-3 Stress Evolution…………………………………………54
3-3-2 Comparison Between Different Thickness of Capped TiN
Layers………………………………………………………55
3-3-2-1 Stress Evolution (In Situ Curvature Measurement)………………………………………………………………………56
3-3-2-2 Phase Transformation (XRD and Four-Point Probe)…………………………………………………………………57
3-3-2-3 Diffusion Behavior (Auger and TEM)…………………59
3-3-2-4 Morphology (TEM)………………………………………61

Chapter 4 Summary…………………………………………………63

References………………………………………………………………64

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