電鏡材料檢測方法ppt課件

1、掃描電子顯微術掃描電子顯微術Scanning Electron Microscopy電子顯微的一個粗略年表電子顯微的一個粗略年表1930年末：第一臺透射電子顯微鏡年末：第一臺透射電子顯微鏡1935年：德國的年：德國的Knoll提出了掃描電提出了掃描電鏡的概念鏡的概念(STEM的概念的概念, 100mm 分分辯率辯率)1938年：年：Von Ardenne開始進行實驗開始進行實驗室研究，室研究，SEM-50 mm分辨率分辨率1942：Zworykin. Hillier, 制成了第制成了第一臺實驗室用的掃描電鏡一臺實驗室用的掃描電鏡 - 今天掃描電鏡的全部基本原理今天掃描電鏡的全部基本原理 - 5

2、0 nm 分辨率分辨率 - 問題問題: 貴貴, 照相曝光時間長照相曝光時間長,電子干擾噪聲）電子干擾噪聲） 結論結論: SEM 不實用不實用!1948：C.W. Oatley, 劍橋大學劍橋大學SEM 的歷史的歷史19381938年年ArdenneArdenne用一個透射電鏡用一個透射電鏡(TEM)(TEM)的光柵電子束第一次推的光柵電子束第一次推斷了斷了 SEM SEM 19421942年年, Zworkin, Zworkin等人第一次為塊狀樣品發(fā)展了等人第一次為塊狀樣品發(fā)展了SEM .SEM .19651965年，第一臺商品年，第一臺商品SEM.SEM.SEMSEM的分辨率被不斷地提高從的

3、分辨率被不斷地提高從1942 1942 年的年的50nm50nm到今天的到今天的0.5nm.0.5nm.SEM SEM 檢測信號用于檢測信號用于 確定成分信息確定成分信息, , 如如 特征特征X-X-射線射線, , 背散射背散射電子電子, ,陰極發(fā)光陰極發(fā)光, , 俄歇電子和樣品電流等。俄歇電子和樣品電流等。第一個掃描電鏡裝置第一個掃描電鏡裝置劍橋大學，劍橋大學，1951年年第一臺商用掃描電鏡第一臺商用掃描電鏡 High Resolution Field Emission SEMSEM images have a natural 3D lookAnd now a look inside the

4、 SEM.SEM-Scanning Electron Microscope (or microscopy)TEM- Transmission Electron MicroscopeAEM- Analytical Electron MicroscopeSTEM- Scanning Transmission Electron MicroscopeEPMA-Electron Probe MicroAnalyzerSPM-Scanned Probe Microscope (STM, AFM)To see a VIRTUAL SEM, go to the following link:micro.mag

5、/primer/java/electronmicroscopy/magnify1/index.htmlSEM 的構造的構造氣動保險閥掃描線圈掃描線圈Signals available from SEMSignalsSEM的主要性能：的主要性能：1，分辨率，分辨率二次電子和俄歇電子的分辨二次電子和俄歇電子的分辨率高，特征率高，特征X射線調制成顯射線調制成顯微圖像的分辨率最低。微圖像的分辨率最低。電子束進入輕元素樣品電子束進入輕元素樣品 滴狀作用體積滴狀作用體積電子束進入重元素樣品電子束進入重元素樣品 半球狀作用體積半球狀作用體積SEM的分辨率即二次電子相的分辨率即二次電子相

6、的分辨率的分辨率電子束進入重元素樣品后，電子束進入重元素樣品后，立即向橫向擴展，因此在分立即向橫向擴展，因此在分析重元素時，即使電子束的析重元素時，即使電子束的束斑很細小，也不能達到較束斑很細小，也不能達到較高的分辨率，此時二次電子高的分辨率，此時二次電子和背散射電子之間的分辨率和背散射電子之間的分辨率的差距明顯變小。的差距明顯變小。影響影響SEM分辨率的三大因素：電子束的束斑大小，檢測信號的分辨率的三大因素：電子束的束斑大小，檢測信號的類型以及檢測部位的原子序數類型以及檢測部位的原子序數SEM分辨率的測定方法：分辨率的測定方法：在已知的放大倍數一在已知的放大倍數一般在般在10萬倍的條件下，萬

7、倍的條件下，把在圖像上測到的最小把在圖像上測到的最小間距除以放大倍數所得間距除以放大倍數所得數值就是分辨率。數值就是分辨率。When theoretically considering the electron probe diameter alone, the higher the accelerating voltage, the smaller is the electron probe. However, there are some unnegligible demerits in increasing the accelerating voltage. They are mainl

8、y as follows:1) Lack of detailed structures of specimen surfaces. 2) Remarkable edge effect. 3) Higher possibility of charge-up. 4) Higher possibility of specimen damage.In SEM, finer surface structure images can generally be obtained with lower accelerating voltages. At higher accelerating voltages

9、, the beam penetration and diffusion area become larger, resulting in unnecessary signals (e.g., backscattered electrons) being generated from within the specimen. And these signals reduce the image contrast and veils fine surface structures. It is especially desirable to use low accelerating voltag

10、e for observation of low-concentration substances.加速電壓對 SEM 像的影響 Always consider Interaction Volume掃描電子顯微術：例子The effect of Accelerating Voltage on SEM Images 30 kV10 kV 5 kV 3 kVSpecimen: Toner 墨粉When high accelerating voltage is used as at (a), itis hard to obtain the contrast of the specimen surfa

11、cestructure. Besides, the specimen surface is easilycharged up. The surface microstructures are easilyseen at (b).(a) 30 kV x 2,500(b) 5 kV x 2,500Specimen: Evaporated Au particles.The image sharpness and resolution are betterat the higher accelerating voltage, 25 kV.(a) 5 kV x 36,000(b) 25 kV x 36,

12、000Specimen: Filter paper.At 5 kV, the microstructures of the specimensurface are clearly seen as the penetration anddiffusion area of incident electrons is shallow.(a) 5 kV x 1,400(b) 25 kV x 1,400Fig. 6 Specimen: Sintered powder.At low accelerating voltage, while surface microstructurescan be obse

13、rved, it is difficult to obtain sharp micrographsat high magnifications. (a) 5 kV x7,200(b) 25 kV x7,200Specimen: Paint coat.When a high accelerating voltage is used, more scatteredelectrons are produced from the constituent substanceswithin the specimen. This not only eliminates the contrastof surf

14、ace microstructures, but produces a differentcontrast due to backscattered electrons from thesubstances within the specimen.(a) 5 kV x2,200(b) 25 kV x2,200SE (secondary electron) imagingHigh resolution (better than 5nm) is obtainable with most SEMsBetter than 2 nm resolution is possible in some case

15、s10 nm resolution is very routine (unless the sample limits the resolution, as is often the case)二次電子： 在入射電子作用下被轟擊出來并離開樣品表面的樣品原子 的核外電子。這也是一種真空自由電子 。 由于原子核和外層價電子間的結合能很小，因而，外層的電子較容易和原子脫離，使原子電離。用IS表示二次電子流。 一個能量很高的入射電子射入樣品時，可以產生許多自由電子。其中90%來自于外層價電子。 特 征： 1)二次電子能量較低。一般不超過50 ev，大部分幾ev；2)來自表層510nm深度范圍；3)對樣

16、品表面化狀態(tài)十分敏感，因此能有效地反映樣品表面的形貌；4)其產額與原子序數間沒有明顯的依賴關系。因而，不能進行成分分析。 成像原理二次電子產額對微區(qū)表面的幾何形狀十分敏感，如下圖，隨入射束與試樣表面法線夾角增大，二次電子產額增大。 因為電子束穿入樣品激發(fā)二次電子的有效深度增加了，使表面5-10 nm作用體積內逸出表面的二次電子數量增多。 根據上述原理畫出二次電子形貌襯度的示意圖 對于實際樣品，表面形貌要比上面襯度的情況復雜得多，但形成二次電子襯度的原理是相同的。 實際樣品中二次電子的激發(fā)過程示意圖 1)凸出的尖棱，小粒子以及比較陡的斜面處SE產額較多，在熒光屏上這部分的亮度較大 2)平面上的S

17、E產額較小，亮度較低。 3)在深的凹槽底部盡管能產生較多二次電子，使其不易被控制到，因此相應襯度也較暗。 Edge effect (secondary electron emission differing with surface condition).Influence of edge effect on image qualityAmong the contrast factors for secondary electrons, the tilt effect and edge effect are both due to the specimen surface morphology

18、. Secondary electron emission from the specimen surface depends largely on the probes incident angle on the specimen surface, and the higher the angle, the larger emission is caused. The objects of the SEM generally have uneven surfaces.There are many slants all over them, which contribute most to t

19、he contrast of secondary electron images. On the other hand, large quantities of secondary electrons are generated from the protrusions and the circumferences of objects on the specimen surface, causing them to appear brighter than even portions.Specimen IC chip.The higher the accelerating voltage,

20、the greater is theedge effect, making the edges brighter.Influence of edge effect on image qualityThe degree of the edge effect depends on the accelerating voltage. Namely, the lower the accelerating voltage, the smaller the penetration depth of incident electrons into the specimen. This reduces bri

21、ght edge portions, thus resulting in the microstructures present in them being seen more clearly.Normally, secondary electron images contain some backscattered electron signals. Therefore, if the tilt direction of the specimen surface and the position of the secondary electron detector are geometric

22、ally in agreement with each other, more backscattered electrons from the tilted portions are mixed, causing them to be seen more brightly due to synergism.(a) 5 kV x720 Tilt Angle: 50(b) 25 kV x720 Tilt Angle: 50Specimen: IC chip.5 kV x1,100The sides of patterns are viewed by tilting the specimen.Th

23、e amount of signals is increased.Use of specimen tilt：a) Dependence of image quality on tilt angle1) Improving the quality of secondary electron images; 2) Obtaining information different form that obtained when the specimen is not tilted, that is, observing topographic features and observing specim

24、en sides. 3) Obtaining stereo micrographs.Fig. 13 shows a photo taken at a tilt angle of 0 (a) and a photo taken at 45 (b). Their comparison shows that the latter is of smooth quality and stereoscopic as compared with the former. When the specimen is tilted, however lengths observed are different fr

25、om their actual values. When measuring pattern widths, etc., therefore, it is necessary to measure without specimen tilting or to correct values obtained form a tilted state.(a) Tilt angle: 0(b) Tilt angle: 45Specimen: Back sides of oleaster leaves. Moreinformation is obtained from stereo-pair photo

26、s.Use of specimen tilt：b) Stereo micrographsWith SEM images it is sometimes difficult to correctly judge their topographical features. In such a case observation of stereo SEM images makes it easy to understand the structure of the specimen. Besides, stereo observation allows unexpected information

27、to be obtained even from specimens of simple structure. In stereo observation, after a field of interest is photographed, the same field is photographed again with the specimen tilted from 5 to 15. Viewing these two photos using stereo glasses with the tilting axis held vertically provides a stereo

28、image.Use of specimen tilt：c) Detector position and specimen directionThe amount of secondary electrons produced when the specimen is illuminated with an electron beam, depends on the angle of incidence theoretically. However, there arises a difference in the image brightness depending on whether th

29、e tilted side of the specimen is directed to the secondary electron detector or the opposite side.With a long specimen, for example, the brightness differs between the side facing the detector and the opposite side.In such a case, directing the longitudinal axis of the specimen to the detector makes

30、 the brightness uniform.Fig. 16 Specimen: FiberDetector position and specimen direction.Specimen: Fiber7kV x2,200Directing the longitudinal axis of the specimen to the secondary electron detector makes the right and left sides equally bright.(An SRT unit is used to direct the image longitudinally.)U

31、se of specimen tilt：c) Detector position and specimen direction(a) Specimen directed as at 1(b) Specimen directed as at 2(c) Specimen directed as at 3Backscattered electrons vary in their amount and direction with the composition, surface topography, crystallinity and magnetism of the specimen. The

32、contrast of a backscattered electron image depends on (1) the backscattered electron generation rate that depends on the mean atomic number of the specimen, (2) angle dependence of backscattered electrons at the specimen surface, and (3) the change in the backscattered electron intensity when the el

33、ectron probes incident angle upon a crystalline specimen is changed.Use of backscattered electron signals背散射電子：背散射電子是指被固體樣品中的原子核或核外電子反彈回來的一部分入射電子。用Ib示背散射電子流。 彈性背散射電子：一般樣品表面原子核反彈回來可達數千至數萬ev。 非彈性背散射電子：電子在固體中經過一系列散射后最終由原子核反彈的或由核外電子產生的，不僅方向改變，能量也有不同程度的損失。其能量分布范圍很寬，數十ev至數千ev。 特征： 1)彈性背散射電子遠比非彈性背散射電子所占的份額

34、多 ；2)能量高，例如彈性背散射，能量達數千至數萬ev ；3)背散射電子束來自樣品表面幾百nm深度范圍 ；4)其產額隨原子序數增大而增多 ；5)用作形貌分析、成分分析原子序數襯度以及結構分析通道花樣）。Retractable BSE detector in chamberObjectivelensSecondary detector (ETD)BSE paths and detector locationsObjectivelensBSE from adjacent regions on flat sampleSEM Compositional imageBackscattered SEM i

35、mage of an PbSn alloy showing contrast based on the atomic number. The brighter areas are Pb-rich.1 背散射電子的襯度原理及應用 背散射電子用于：1形貌分析來自樣品表層幾百nm范圍2成分分析產額與原子序數有關3晶體結構分析基于通道花樣襯度1BE形貌襯度特點1用BE進行形貌分析時，其分辨率遠比SE像低。2圖象襯度很強，襯度太大會失去細節(jié)的層次。下圖是檢測器接收BE和SE的情況BE能量高，以直線軌跡逸出樣品表面，對于背向檢測器的樣品表面，因檢測器無法收集到BE而變成一片陰影，因而，其圖象襯度很強，襯度

36、太大會失去細節(jié)的層次，不利于分析。因而，BE形貌分析效果遠不及SE，故一般不用BE信號2BE原子序數襯度原理 原子序數Z與背散射電子產額的關系如圖。E40，對E十分敏感。進行分析時，樣品上原子序數較高的區(qū)域中由于收集到的背散射電子數量較多，故在熒光屏上的圖象較亮。因而，利用原子序數造成的襯度變化可以對各種金屬和合金進行定性的成分分析。需注意以下二點： 1用BE進行成分分析時，為避免形貌襯度對原子序數襯度的干擾，被分析的樣品只進行拋光，而不必腐蝕。2既進行成分分析又要進行形貌分析時，可采用對稱分布的檢測器收集信號同一部位的BE），然后計算機處理分別得到形貌信號和成分信號。如下圖。a成分有差別，形

37、貌無差別b形貌有差別，成分無差別c成分形貌都有差別 相加為成分像相減為形貌相The backscattered electron image contains two types of information:one on specimen composition and the other on specimentopography. To separate these two types of information, a paired semiconductor detector is provided symmetrically with respect to the optical

38、axis. Addition of them gives a composition image while subtraction gives a topography image. And with composition images of crystalline specimens, the difference in crystal orientation can be obtained as the so-called “channeling contrast,” by utilizing the advantage that the backscattered electron

39、intensity changes largely before and after Braggs condition.Use of backscattered electron signalsPrinciples of composition image and topography imageSE versu BSE images of alloyObjectivelensCu/Zn Alloy, SE (left), BSE (right).0.1 Atomic Number Difference.6.2 吸收電子成像的襯度原理及應用 如前所述，吸收電子產生的電流 當樣品很厚，It =

40、0，那么： 所以，吸收電子象的襯度是與背散射電子和二次電子像的襯度是互補的。 實際上，SE信號與原子序數沒有明顯關系，因而，可以認為，背散射電子像和吸收電子像襯度正好相反。The generation region of backscattered electrons is larger than that of secondary electrons, namely, several tens of nm. Therefore, backscattered electrons give poorer spatial resolution than secondary electrons. B

41、ut because they have a larger energy than secondary electrons, they are less influenced by charge-up and specimen contamination.Use of backscattered electron signalsTOPOX-ray (Si)X-ray (Al)BEISEICOMPOSpecimen: Slug20kV x1,100The backscattered electron image is important also as a supplementary means

42、 for x-ray analysis.Influence of charge-up on image quality Specimen: Resist.Charge-up can be prevented by properly selecting the accelerating voltage.(a) 1.0 kV x3,200(a) 4 kV(b) 10 kV(b) 1.3 kV x3,200Specimen: Foreleg of vinegar fly.Charge-up can be reduced by using low accelerating voltage.Specim

43、en damage by electron beamSpecimen: Compound eye of fly. 5 kV x1,00When a specimen area is irradiated with an electron probe for a long time at high magnification, it may be damaged as shown in (b).(b)(a)ContaminationWhen the electron probe is irradiated on a specimen portion fora long time, its ima

44、ge may lose sharpness and become dark. Thisis caused by the residual gas in the vicinity of the specimen beingstruck by the electron probe. This phenomenon is called specimencontamination.The conceivable residual gases in the specimen chamber, whichcause contamination are:1) Gas caused from the inst

45、rument itself.2) Gas that specimens bring into the instrument3) Gas that the specimen itself gives off.Specimen: ITO.A x18,000 photo taken after a long-time electron probe scanning at x36,000. As compared with the clear image of peripheral region, the middle region shows reduced contrast and lacks i

46、mage sharpness.5 kV x18,000電子探針顯微分析X-ray Microanalysis Comparison of Energy Dispersive Spectroscopy EDS能譜儀能譜儀 and Wavelength Dispersive Spectroscopy spectra WDS波譜儀波譜儀能譜儀成分分析的特點能譜儀成分分析的特點:優(yōu)點優(yōu)點:1, 探測探測X射線的效率高，射線的效率高，( 探頭與樣品近探頭與樣品近,不必不必通過分光晶體衍射通過分光晶體衍射)能譜儀的靈敏度比波譜儀能譜儀的靈敏度比波譜儀高一個數量級。高一個數量級。2, 可在同一時間內對分析點

47、內所有元素可在同一時間內對分析點內所有元素x射線射線光子的能量進行測定和計數，幾分鐘內可得光子的能量進行測定和計數，幾分鐘內可得到定性分析結果到定性分析結果,而波譜儀只能逐個逐個測量而波譜儀只能逐個逐個測量每種元素的特征波長。每種元素的特征波長。3, 結構簡單，沒有機械傳動部分，因此穩(wěn)定性結構簡單，沒有機械傳動部分，因此穩(wěn)定性和重復性都很好。和重復性都很好。4, 不必聚焦，對樣品表面沒有特殊要求，適合不必聚焦，對樣品表面沒有特殊要求，適合于粗糙表面的分析工作。于粗糙表面的分析工作。缺點缺點:1，分辨率低于波譜儀。，分辨率低于波譜儀。 EDS: 160eV WDS:510eV2，只能測試，只能測

48、試Z大于大于11的元素的元素,而波譜儀可測而波譜儀可測Z從從4到到92間的所有元素。間的所有元素。 EDS里里Si(Li)探測器的鈹窗口限制探測器的鈹窗口限制3， Si(Li)探測器必須要液氮冷卻。探測器必須要液氮冷卻。 電子探針的主要功能就是進行微區(qū)成分分析。它是在電子光學和X射線光譜學原理的基礎上發(fā)展起來的一種高效率分析儀器。 其原理是：用細聚焦電子束入射樣品表面，激發(fā)出樣品元素的特征X射線，分析特征X射線的波長或能量可知元素種類；分析特征X射線的強度可知元素的含量。其鏡筒部分構造和SEM相同，檢測部分使用X射線譜儀，用來檢測X射線的特征波長波譜儀和特征能量能譜儀），以此對微區(qū)進行化學成分

49、分析。 EPMA的結構和工作原理：的結構和工作原理：電子探針的信號檢測電子探針的信號檢測系統(tǒng)是系統(tǒng)是X射線譜儀射線譜儀6.2.2 能量分散譜儀能譜儀能量分散譜儀能譜儀EDS） 1. 工作原理工作原理 利用不同元素利用不同元素X射線光子特征能量不同特點進行成分分析射線光子特征能量不同特點進行成分分析 鋰漂移硅能譜儀鋰漂移硅能譜儀Si(Li)框圖框圖 X-ray Microanalysis Overview of EDS system 電子絕緣體場效應晶體管能譜儀成分分析的特點能譜儀成分分析的特點:優(yōu)點優(yōu)點:1, 探測探測X射線的效率高，射線的效率高，( 探頭與樣品近探頭與樣品近,不必不必通過分光晶體衍射通過分光晶體衍射)能譜儀的靈敏度比波譜儀能譜儀的靈敏度比波譜儀高一個數量級。高一個數量級。2, 可在同