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研究生：	劉純宇 Liu, Chung-Yu
論文名稱：	BiFeO3鐵電薄膜之製備與特性研究 Fabrication and Characterization of BiFeO3 Ferroelectric Thin Films
指導教授：	陳貞夙 Chen, Jen-Sue
學位類別：	碩士 Master
系所名稱：	工學院 - 材料科學及工程學系 Department of Materials Science and Engineering
論文出版年：	2006
畢業學年度：	94
語文別：	中文
論文頁數：	88
中文關鍵詞：	電子陶瓷、磁性、鐵電材料、鐵電記憶體
外文關鍵詞：	magnetoelectric, ferroelectric material, ferroelectric, BiFeO3, thin film
相關次數：	點閱：93 下載：14
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　　本研究利用反應性磁控濺鍍法沉積BiFeO3做為FeRAM中鐵電薄膜之材料；由於BiFeO3有極高的漏電流，故本實驗探討在BiFeO3中加入兩種不同量的BaTiO3分別製作成BiFeO3、(BiFeO3)0.7 -(BaTiO3)0.3、 (BiFeO3)0.5-(BaTiO3)0.5固溶體靶材，並探討三種不同靶材所製備出薄膜之特性。
　　本研究使用低掠角X光繞射儀(GIAXRD)對薄膜的結構及結晶性進行分析，使用拉塞福背向散射分析儀(RBS)做薄膜組成成份與密度之分析，使用X光光電子能譜儀進行化學鍵結狀態分析，利用振動樣品量測儀(VSM)量測薄膜之磁化率。在電性量測方面，吾人將其製作成Pt/(BiFeO3)x-(BaTiO3)1-x /Pt/Ti/SiO2/Si結構，使用鐵電量測儀量測薄膜的鐵電性；並利用Picoampere meter量測I-V曲線，以瞭解其漏電性質。
　　由實驗結果發現，Bi2O3 + Fe2O3粉末經過兩次煆燒再以硝酸清洗的步驟後，可以消除不必要之雜相，較容易製作出具純BiFeO3相的靶材。由GIAXRD的結果發現，初鍍的 (BiFeO3)x-(BaTiO3)1-x薄膜仍是非晶狀態，但經過700 oC熱處理後將有明顯的繞射峰出現。由RBS的結果可以發現，薄膜的理論密度會隨著BaTiO3量的增多而增加，這和(BiFeO3)x-(BaTiO3)1-x塊材之理論密度會隨BaTiO3的含量增加而減少的趨勢相反。另外，由VSM量測結果發現，利用(BiFeO3)0.7-(BaTiO3)0.3靶材所沉積而得的薄膜，經700 oC、十分鐘的熱處理後，具有殘留磁化率，同時發現如果將熱處理時間拉長將有更大的殘留化率。在電性量測方面，經過熱處理後的試片，其PE曲線皆無法形成一個完整的電滯曲線，且漏電流都有隨熱處理溫度上升而明顯增加的趨勢。

　In this study, BiFeO3 thin films were deposited by reactive magnetron sputtering system as the ferroelectric films in FeRAM. Because of the significant leakage of BiFeO3, three (BiFeO3)x-(BaTiO3)1-x solid solution targets of various compositions were prepared for film deposition and the material properties of the (BiFeO3)x-(BaTiO3)1-x films were characterized.
　The crystalline structure of thin films was characterized by glancing incident angle X-ray diffraction(GIAXRD). The composition and the mass density were determined by Rutherford backscattering spectrometry (RBS). The chemical bonding structure of films was determined by X-ray photoelectron spectroscopy (XPS). Magnetization of the sample was measured by using the vibrating sample magnetometer (VSM). In addition, the sample was made to the Pt /(BiFeO3)x -(BaTiO3)1-x /Pt/Ti/SiO2/Si structure for electrical measurements. Ferro- electric analyzer was used to measure the ferroelectric property of thin films, and picoampere meter was used to determine the leakage current.
　After calcining powders of Bi2O3 and Fe2O3, nitric acid was used to wash away the secondary phases. By this way, we can obtain the pure BiFeO3 target. According to GIAXRD result, the as deposited films are amorphous, but diffraction peaks are observed in the samples after annealing at 700oC for 10 min. from the result of RBS, analysis reveals that the mass density of (BiFeO3)0.7-(BaTiO3)0.3 thin films increases when the BaTiO3 content increases. The VSM result indicates that (BiFeO3)0.7-(BaTiO3)0.3 thin film possesses remenant magnetization after annealing at 700 oC. As heat treatment time increases, the degree of remenant magnetization increases, too. In PE curves of all annealed thin films do not present any hystersis loop. Finally, IV measurement shows that the leakage current of (BiFeO3)x-(BaTiO3)1-x films increases as the annealing temperature increases.

目錄
第1 章 緒論...........................................................................................1
1-1 前言...........................................................................................1
1-1-1 電子記憶體[1][2][3] ............................................................1
1-1-2 鐵電薄膜.........................................................................1
1-2 研究目的...................................................................................3
第2 章 理論基礎...................................................................................9
2-1 介電性與極化[19][20][21] ..............................................................9
2-1-1 極化現象與介電常數.....................................................9
2-1-2 極化機制以及頻率特性[23].............................................9
2-2 鐵電滯迴曲線.........................................................................12
2-3 磁性原理簡介[24] .....................................................................17
2-4 BiFeO3 基本性質.....................................................................23
2-4-1 晶體結構[9][25][26][27] .......................................................23
2-5 BiFeO3 相關文獻回顧.............................................................29
第3 章 實驗方法與步驟.....................................................................30
3-1 實驗材料.................................................................................30
3-1-1 製作(BiFeO3)x-(BaTiO3)1-x 靶材所需粉末...................30
3-1-2 金屬靶材.......................................................................30
3-1-3 基材...............................................................................31
3-1-4 製備薄膜所需氣體.......................................................31
3-2 實驗設備.................................................................................32

3-2-1 陶瓷靶材製程設備.......................................................32
3-2-2 磁控濺鍍系統(Magnetron sputtering system) .............33
3-2-3 乾式熱氧化系統(Dry oxidation system)......................34
3-2-4 氣氛退火系統(Atmospheric Annealing System) .........35
3-2-5 電子槍蒸鍍系統(E-beam evaporation)........................36
3-3 實驗流程.................................................................................37
3-3-1 靶材製備.......................................................................37
3-3-2 基材清洗.......................................................................40
3-3-3 退火製程.......................................................................41
3-3-4 (BiFeO3)x-(BaTiO3)1-x 薄膜製備及分析.......................42
3-4 電性基板製備與上電極之製作及分析.................................44
3-5 分析儀器.................................................................................46
3-5-1 膜厚量測.......................................................................46
3-5-2 X 光繞射儀...................................................................47
3-5-3 低掠角X-ray 薄膜晶體結構分析(Glancing incident
angle XRD,GIAXRD) ..............................................................47
3-5-4 掃瞄式電子顯微鏡(SEM)—薄膜表面型態分析........48
3-5-5 拉塞福背向散射分析儀[43][44][45] (Rutherford
backscattering spectrometry, RBS)...........................................49
3-5-6 X-ray 光電子能譜分析儀(X-ray Photo-electron
Spectroscopy, XPS)[43] ..............................................................50
3-5-7 磁化率量測儀器(Vibrating sample
magnetometer ,VSM) ...............................................................51
3-5-8 IV 及電性量測..............................................................52
3-5-9 TF2000 鐵電薄膜量測儀.............................................52
第4 章 結果與討論.............................................................................53
4-1 靶材製備.................................................................................53

4-2 薄膜材料晶體結構分析.........................................................56
4-3 (BiFeO3)x-(BaTiO3)1-x 薄膜成分比例分析............................59
4-4 (BiFeO3)x-(BaTiO3)1-x 薄膜化學鍵結分析.............................68
4-5 (BiFeO3)x-(BaTiO3)1-x 薄膜磁化率分析................................71
4-6 (BiFeO3)x-(BaTiO3)1-x 薄膜電性分析....................................74
4-6-1 P-E measurement...........................................................74
4-6-2 I-V 量測........................................................................76
4-7 SEM 表面型態分析...............................................................78
第5 章 結論.........................................................................................81
第6 章 參考資料.................................................................................83

圖目錄
Fig. 1-1FeRAM 示意圖[5]...........................................................................6
Fig. 1-2 電子陶瓷屬性關係圖..................................................................7
Fig. 1-3 原始鐵電記憶模型[6]....................................................................8
Fig. 1-4 鐵電薄膜與薄膜與矽晶片結合之記憶體結構[6] .......................8
Fig. 1-51T-1C type 鐵電記憶體電路圖[6] ................................................8
Fig. 2-1 四種不同的極化示意圖[22] ........................................................10
Fig. 2-2 介電常數隨頻率變化之示意圖[23] .........................................11
Fig. 2-3 理想鐵電材料電滯曲線圖[20] ....................................................14
Fig. 2-4 BaTiO3 鐵電晶體結構隨溫度改變示意圖(a)居禮溫度之上(b)
居禮溫度之下。[22] ..................................................................................15
Fig. 2-5 BaTiO3 隨溫度改變其晶體結構和自發性極化之值變化。[4].16
Fig. 2-6 各種磁性樹狀關係圖[24] ............................................................20
Fig. 2-7 各種磁性之磁矩排列和溫度關係圖[22] (a) 順磁現象(b)鐵磁
現象(c)反鐵磁現象 (d)亞鐵磁現象.......................................................21
Fig. 2-8 常見過渡元素與能帶關係圖[4].................................................22
Fig. 2-9 Rhombohedral and hexagonal 單位晶格互換於rhombohedral
晶格[28] ......................................................................................................24
Fig. 2-10 BiFeO3 晶體結構圖[29] ..............................................................25
Fig. 2-11 各種不同扭曲的鈣鈦礦結構於溫度高於居温度時轉換為理
想鈣鈦礦結構之示意圖[29] ......................................................................26
Fig. 2-12 標準BiFeO3 XRD 繞射圖譜(ICDD PDF 20-0169)...............27

Fig. 2-13 標準BaTiO3 XRD 繞射圖譜(ICDD PDF 05-0626)...............27
Fig. 2-14 BiFeO3 塊材和薄膜結構比較圖[11]..........................................28
Fig. 3-1 磁控濺鍍裝置圖.........................................................................33
Fig. 3-2 乾式氧化爐裝置圖.....................................................................34
Fig. 3-3 氣氛爐管裝置圖.........................................................................35
Fig. 3-4 電子槍蒸鍍系統圖[40] ...............................................................36
Fig. 3-5 靶材製備流程圖........................................................................39
Fig. 3-6 基板清洗步驟圖.........................................................................40
Fig. 3-7 退火製程流程圖.........................................................................41
Fig. 3-8 薄膜製備及其分析圖................................................................43
Fig. 3-9 電性量測示意圖.........................................................................44
Fig. 3-10 電性量測流程示意圖..............................................................45
Fig. 3-11α-step 量測示意圖.....................................................................46
Fig. 3-12 拉塞福背向散射儀示意圖[43] .................................................49
Fig. 3-13 VSM 裝置示意圖.....................................................................51
Fig. 4-1 使用不同的Bi2O3 及Fe2O3 混合比例，所製備出之靶材的X 光
繞射圖譜純相BiFeO3 靶材製作比較圖................................................54
Fig. 4-2 (BiFeO3)x-(BaTiO3)1-x 靶材比較圖...........................................55
Fig. 4-3 BFO-BTO 薄膜於Si 基板之上之GIAXRD 比較圖...............57
Fig. 4-4 BFO-BTO 薄膜於Pt 基板之上之GIAXRD 比較圖...............58
Fig. 4-5 Ti、Fe 面積取法示意圖............................................................63
Fig. 4-6 利用三種不同靶材鍍製之薄膜，在熱處理前後之Bi 4f 束縛能
變化...........................................................................................................69
Fig. 4-7 各試片鐵元素之XPS 能譜圖(a)BiFeO3
(b)(BiFeO3)0.7-(BaTiO3)0.3 (c) (BiFeO3)05-(BaTiO3)0.5 ..............................70
Fig. 4-8 (BiFeO3)x-(BaTiO3)1-x 薄膜磁化率比較圖...............................72
Fig. 4-9(BiFeO3)0.7-(BaTiO3)0.3 薄膜以700oC 熱處理不同時間比較圖73

Fig. 4-10 各初鍍膜試片之PE................................................................75
Fig. 4-11 (BiFeO3)x-(BaTiO3)1-x 漏電流比較圖.......................................77
Fig. 4-12 薄膜濺渡於Si 基板表面形態圖.............................................79
Fig. 4-13 薄膜濺鍍於Pt 基板表面型態圖.............................................80
Fig. 4-14 Pt/Ti/SiO2/Si 基板表面形態圖.................................................80

表目錄
Table. 1-1DRAM 技術演進圖[7] ................................................................5
Table. 1-2 常見高介電常數薄膜[7] ............................................................7
Table. 3-1 靶材製備所需之藥品列表.....................................................38
Table. 3-2 靶材燒結溫度和時間表.........................................................38
Table. 4-1RBS 各試片積分面積、散射截面和成分比例.....................62
Table. 4-2 各試片組成密度和厚度.........................................................64
Table. 4-3 (BiFeO3)0.7-(BaTiO3)0.3 薄膜以700oC 熱處理.......................73
                                    

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