本研究以封閉式磁控濺射系統鍍著氮化鋁(AlN)薄膜於矽晶片上，利用X光繞射分析儀(XRD)、掃瞄式電子顯微鏡(SEM)、穿透式電子顯微鏡(TEM)、原子力顯微鏡(AFM)、光電子能譜儀(XPS)和電子能量耗失能譜儀(EELS)，探討鍍膜在脈衝功率為900W、1000W與沈積時間為120min、360min條件下以及試片經過不同溫度氧化後，其微結構與化學成分變化情況。
在改變製程條件方面，由XRD結果得知，在較高的脈衝功率和較長的沈積時間下，鍍膜具有較佳的(002)優選方向，由SEM與TEM橫截面試片的觀察發現鍍膜呈現柱狀晶結構(columnar structure), 其晶粒尺寸隨著遠離基材的距離、鍍著功率與沈積時間增加而增加。AFM分析指出鍍膜的表面粗糙度隨沈積時間而增加, 其粗糙度平均值Ra介於1.0與6.0 nm之間，適合作為表面聲波元件(Surface acoustic device)材料之用。XPS與能量散佈光譜儀(EDS)分析提供鍍膜的化學組成與鍵結狀態。
另外在鍍膜氧化方面，由SEM的二次電子影像中發現, 氧化溫度低於900℃的試片, 其表面顏色與形貌與剛鍍著的試片相似, 鍍膜表面在1000℃氧化後，鍍膜表面出現大量角狀顆粒的形貌，粗糙度也隨氧化溫度昇高而增加。由氮化鋁膜橫截面TEM試片影像中得知，鍍膜試片經高溫氧化後於鍍膜表面生成一層等軸晶結構之氧化鋁層，隨氧化溫度昇高，等軸晶晶粒尺寸隨之成長。此外，由XRD與TEM繞射結果得知，氧化物開始出現於700℃氧化的試片中，經1000℃高溫氧化後，部分的AlN相轉換變成過渡相δ-Al2O3 與熱力學穩定相α-Al2O3的混合物，在氧化溫度為1100℃以上的試片中，AlN已完全相轉換成α-Al2O3。Aluminum nitride (AlN) coatings were produced by a closed field unbalanced magnetron (CFUBM) sputtering system on a type (001) Si wafer. Processing parameters of the deposition system were manipulated to study the evolution of the microstructure and properties of the AlN coatings. Characterization of the microstructure, chemistry, and thermal stability of the AlN-coated silicons and those oxidized at elevated temperatures in the range of 300~800℃ was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), plan-view and cross-section transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), electron energy loss spectroscopy (EELS), and EELS mapping.
X-ray diffraction results show that the thin films exhibit enhanced (002) preferred orientation at higher pulse power and longer deposition time. It is also obtained that the AlN films have a columnar structure and that the size of the columns increases with the distance from the substrate pulse power, and the deposition time, as revealed by SEM and TEM. AFM analysis indicates that the surface roughness of the coatings increases with the deposition time. The surface of the thin films is smooth with an average roughness Ra = 1.0~6.0 nm, which is suitable for application in surface acoustic wave devices. XPS analysis gives the chemical composition of the coatings as well as the bonding states of the elements. Moreover, Energy dispersive spectroscopy (EDS) analysis gives the chemical composition of the coatings as well as the percentage content of the elements.
For the oxidized AlN coatings, it was observed that the surface morphology and the color of the nitride specimens oxidized below 900℃ remains similar to the as-deposited specimen. A great amount of granular particles are present in the 1000℃ oxidized specimens and the roughness of the coating surfaces increases with the oxidation temperature. Cross-section TEM reveals that oxidation of the nitride-coated silicon at elevated temperatures produces an Al2O3 with an equiaxed grain structure on the coating surface, and the average grain size of the layer increases with the oxidation temperature. From XRD and TEM results, it is obtained that oxidation of the nitrides to form an Al2O3 oxide layer was initially observed in the specimen oxidized at 700℃. Phase transformation from partially AlN into the mixed oxides of δ-Al2O3 andα-Al2O3 in the coatings occurred at 1000℃ and the transformation into α-Al2O3 was completed at 1100℃.摘要…..…………………………….……………………….……………….. Ⅰ
Abstract…………………………….……………………….……………….. Ⅱ
Contents…………………………………...………………….……………... Ⅳ
List of Tables………………………………..……………….………………. Ⅶ
Figure Captions………………..……………………………..……………... Ⅷ
Chapter 1. Introduction………………..…………………………………… 1
References…………………………………………………………………… 8
Chapter 2. Theoretical basis………………………………………….……. 10
2.1 Magnetron sputtering……...……………………………………….. 10
2.1.1 Conventional magnetron sputtering………...………………... 10
2.1.2 Unbalanced magnetron sputtering……………………………. 12
2.1.3 Closed-field unbalanced magnetron sputtering……..……….. 13
2.2 Structure zone model……………………………………………….. 17
2.3 Properties of Aluminum nitride…………………………………….. 22
2.4 Oxidation mechanism of AlN coatings…………………………..…. 27
2.4.1 Wagner''s parabolic oxidation theory………………………….. 28
2.4.2 Oxidation Behavior of AlN Coatings……………………….…
29
2.4.3 Phase evolution in the AlN coatings during tempering………..
31
2.5 Electron energy loss spectroscopy in transmission electron microscope………………………………………………………….. 32
2.5.1 Interactions of electron with specimen……………………….. 32
2.5.2 Electron energy loss spectrum………………………………... 34
2.5.3 The energy loss near-edge structure (ELNES) and the extended energy loss fine structure (EXELFS)………………. 38
References…………………………………………………………................ 41
Chapter 3. Experimental procedure………..……………………………… 47
3.1 Deposition of AlN coatings…………………………………………. 48
3.1.1 Substrate preparation………………………………….……… 48
3.1.2 Deposition using a closed-field unbalanced magnetron sputtering system……………………………………...…….... 48
3.2 Oxidation of AlN coatings……….………………………………… 49
3.3 Characterization of AlN coatings……….………………………..… 49
3.3.1 X-ray diffraction (XRD) analysis………………………….…. 49
3.3.2 Surface analysis by scanning electron microscopy (SEM) and atomic force microscopy (AFM)……………………………... 49
3.3.3 Microstructure and chemistry analysis by transmission electron microscope (TEM)………………………………….. 50
3.3.4 Chemical shift analysis of the coatings by X-ray photoelectron spectroscopy (XPS)………………….……….. 51
Chapter 4. Results and discussion…...…..……….………………………... 53
4.1 Microstructure and chemistry of the AlN coatings………………..... 53
4.1.1 Effect of pulse power…………………………………………... 53
4.1.1.1 X-ray diffraction analysis.………..………………….…. 53
4.1.1.2 SEM morphology………………………………….….... 55
4.1.1.3 Plan-view TEM………………………………………… 57
4.1.1.4 Cross-section TEM……………………………………... 60
4.1.1.5 AFM analysis….……………………………………...... 63
4.1.2 Effect of deposition time……..………………………….……... 65
4.1.2.1 X-ray diffraction analysis.……….…..……………....…. 65
4.1.2.2 SEM morphology…………………………………..…... 66
4.1.2.3 Plan-view TEM……………………………………....… 68
4.1.2.4 Cross-section TEM………………………….………..... 71
4.1.2.5 AFM analysis……………………………..…………...... 71
4.1.2.6 X-ray photoelectron spectroscopy…………...………..... 74
4.1.2.7 EDS analysis…………...……………………...…..…..... 77
4.1.2.8 EELS analysis…………...………………………...…..... 78
4.2 Oxidation behavior of the AlN coatings……………………………. 81
4.2.1 X-ray diffraction analysis.………..……………………..….…. 81
4.2.2 SEM morphology……………………….…………..…….….... 83
4.2.2.1 Surface morphology…………………………………….
83
4.2.2.2 Cross-sectional morphology……………………………
96
4.2.3 Plan-view TEM……………………………………………….. 98
4.2.4 Cross-section TEM…………………………………………..... 110
4.2.5 AFM analysis….……………………………………................. 126
4.2.6 Elemental analysis by EELS…………………………………... 129
4.2.7 Composition depth profiling analysis by EELS mapping…….. 131
References……………………………………………………..…................. 134
Chapter 5. Conclusions………………………………………………...…... 138
Appendix……………………………………………………….….……….... 140
Publication list……………………………………………………………..... 14
