Scanning Electron Microscopy (FEI Versa 3D Dual Beam)

Transcription

1 Scanning Electron Microscopy (FEI Versa 3D Dual Beam) This operating procedure intends to provide guidance for basic measurements on a standard sample with FEI Versa 3D SEM. For more advanced techniques or imaging in environmental SEM mode, please contact NCC staff members. Log On to the System 1. Please use your RCS ID to logon to the computer. 2. You will see a counter on the screen, minimize this screen. Do not forget to logout when your session ends. Starting the System 1. Type the username and password on the xtm Log On screen. The application status window will appear, click on hide. 2. The screen now shows the previous imaging parameters. Each of the quadrants corresponds to: E-beam, I-beam, Nav-Cam, CCD camera. Note: Operations are made on the active quad highlighted in blue. (Example: First quadrant, e-beam in Figure 1) Figure 1: Main screen, each of the quadrants corresponds to: Quadrant 1 (E-beam), Quadrant 2 (Ibeam), Quadrant 3 (Navigation Camera (Nav-Cam)), Quadrant 4 (CCD camera), Top panel and <Tabs> in the Right panel is to adjust parameters 1

2 Sample Loading 1. To load the sample, vent the chamber first. VENT button is located on the first tab on the right of the screen,, on the <Beam Control> tab,, on the right panel. Once hit, the button will turn into yellow and the venting will take 3min. In addition, the diagram on the bottom right turns into orange,, indicating that it is being vented. Wait until the venting process is completed. 2. Open the chamber door, (i) place the stub, (ii) using the hexagonal screw driver, finger tight the stub to the base, (iii) Then click on PUMP on the <Beam Control> tab,, on the right panel. (Figure 2) Figure 2. Loading the sample (i) place the stub, (ii) tighten to the base (iii) support the chamber door and click on PUMP 3. The button will turn into yellow, and the chamber on the diagram will turn orange,, wait until the chamber pressure is stabilized and diagram turns green,. Figure 3. Setting up the high-vacuum in the chamber Moving the stage 1. Hide the Application Status bar. Live sample movements can be observed in the fourth quadrant (CCD camera). To move the stage: 2

3 a. Either type in on the <Navigation> tab,, second from the left, the red arrow right next to Z indicates that the stage is not linked, the reference distance is the base of the sample chamber. Start typing 30mm, which raises the stage, then type in 40mm, then raise the stage gradually until you reach 5 mm below 10mm working distance line (yellow line on the CCD camera) (Figure 4A) b. Other option is to use the mouse, click and hold on the wheel, and slowly drag the mouse. Yellow bar and an arrow will appear on the fourth quadrant. (Figure 4B) Figure 4. (A) Raising the stage by typing on the <Navigation> tab, (B) Raising the stage by mouse click 2. Go to <Stage> menu at the top of the window and click on <take a nav-cam photo>. (Figure 5) This will bring the sample under the navigation camera, take a photo (appears on the third quadrant (Nav-Cam)) and bring the sample to original position. Figure 5. (A) Click on the take a nav-cam photo on the top menu (B) The sample appears on the third quadrant (Nav-Cam) (C) The stage comes back to original position 3

4 3. Navigate on the sample on the third quad, to record a specific position, doubleclick on a point on a point of interest and add this position using the ADD button on the <Navigation> tab,. Starting the Beams 1. To start the beams, activate the corresponding window and on the <Beam Control> tab, click on BEAM ON button. Yellow BEAM ON button means, it is activated. (Do not forget the click on BEAM ON button before leaving) <Beam Control> tab BEAM ON button 2. If you are planning to make Pt deposition, it should be heated up. To heat up Pt, <Patterning> tab,,on the right panel, and double click on Cold. It will turn into yellow as it heats up, be advised that you should wait for 10 min to stabilize. Linking the Stage 1. Turn on the e-beam. Click on the unpause button on the first quadrant (e-beam),. 2. Raise the stage to working distance to 10mm by mouse (click and hold the wheel and drag on the fourth quad until the sample surface reached WD = 10mm, yellow bar). 3. Adjust the focus (coarse and fine knobs), brightness and contrast (B/C) using the knobs on the control bar. (Figure 6) 4

5 Figure 6. Manual Control Bar 4. Adjust the magnification to 2000X and re-focus. (Figure 7) 5. Link the stage, using the fourth button at the top bar,. The red arrow on the <Navigation> tab should turn into gray, once the stage is linked. (Figure 7) 6. Once the stage is linked, re-link the stage as much as you wish, especially after making large stage movements. If you have multiple samples with different heights, relink the stage as you move. Figure 7. Linking the stage (i) Raise the stage to WD = 10mm, (ii) Focus on a feature at 2000X, adjust brightness and contrast using the knobs on the control bar, (iii) Link the stage (iv) Make sure the red arrow on the <Navigation> tab turns into gray. 5

6 High Resolution E-beam Imaging 1. Make sure first quadrant (e-beam) is active window, then check the detector from the <Detectors> tab, the right panel as ETD Secondary Electrons., on 2. On the point of interest in the first quadrant, increase the magnification by the knobs on the control bar. Navigation on the sample surface is made by double clicking on a point, or click and hold mouse wheel and drag. 3. Starting parameters (Figure 8) a. Select an appropriate voltage (10kV or 20kV) and adjust the spot size to 5. b. Every time you change the spot size, the B/C will change, you may re-adjust them by the knobs, if you get lost, try using the auto brightness/contrast button,. c. If you prefer to work on a reduced area,, (the top third button from the left), or you may change the dwell time to 300 ns and the resolution. Figure 8. Parameters Setting buttons in the top panel 4. Adjust focus, brightness/contrast, stigmation and lens modulator iteratively. (Figure 9) a. Focus: Using the knobs (coarse and fine) on the control bar, or use the mouse: hold the right click and drag left and right. b. Brightness and contrast (B/C): Using the knobs on the control bar, or use the bar on the <Beam Control> tab,, on the right panel. c. Stigmatism: Using the knobs (X and Y stigmator) on the control bar, or use the mouse: hold (shift+right click) and drag to left-right (X stigmator) and up-down (Ystigmator) or use the panel on the <Beam Control> tab,, on the right panel. d. Lens alignment: Using the Direct Adjustment button at the top panel,, click on lens modulator. Working on a reduced area, amplitude if needed., is easier; change the 6

7 Figure 9. (i) Working in a reduced area, (ii) Adjusting B/C and stigmators on the right panel, (ii) Lens Modulator adjustment via Direct Adjustments Saving Image 1. Click on the arrow on Image Acquisition button at the top of the window, and take a photo. This will save the image on the pre-set quality and scanning parameters, (dwell time:10 us, Resolution: 3072x2048) 2. You may measure the features by clicking the Direct measurements button at the top of the window, delete them by keyboard. 3. Save the image with the measurement on the save as window: a. Save image with Databar, saves the information on the screen as a databar b. Save image with overlaid graphics saves the image with the measurement and text. Please save your results to Network>SPC-VE52>Shared Data to a folder by your full name and surname. 7

8 Back-Scattered Electron Imaging 1. On the second (I-beam) quad, left click on the i-beam icon on the bottom left corner and change it to e-beam icon. 2. Highlight the first (e-beam) quad and select your point of interest and focus on the image and link the stage (this is very important!) 3. Highlight the second quad, then go to <Detectors> tab,, and select Detector as CBS (Concentric Back Scattered Electron Detector) and then click on INSERT button. 4. The incoming CBS detector interferes with the CCD camera, the live image will be paused, unpause the fourth quadrant (CCD camera). 5. Once the CBS detector is in, you may see it coming from left. The CBS detector will change the B/C of your image on e-beam quad. While working with both ETD and CBS detectors, adjusting focus will affect both images, only brightness and contrast adjustments can be made separately. Auto-brightness button adjusts both quads. 6. To combine secondary and back-scattered imaging, change the third quadrant (Nav-Cam) to e-beam, by clicking the icon on the bottom left, this will combine the secondary and back-scattered images in a single window (third quadrant). The detector is now MIX, where you may adjust the colors of the ETD and CBS by sliding the bar. 7. You may separately collect images from the ETD and CBS detectors by Image Acquisition button. 8. Once finished, highlight the second quad, go to <Detectors> tab and retract the CBS detector. Then, go to fourth quadrant (CCD cam) and unpause it and receive live image from your sample. 8

9 Setting Eucentric Position At the eucentric position, the stage tilt and the beam axes intersect. When the stage is tilted or rotated in any direction, this point remains focused and almost does not shift. 1. To check the eucentric point, make sure you performed all the steps in moving and linking the stage and high resolution e-beam imaging. Follow the instructions below (Figure 10): i. Set the working distance to 10mm by typing in the Z on the <Navigation> tab, ii. pick and center a feature at 10kX focus on the image in the first quad and iii. link the stage. iv. Then type the tilt angle as 5. Check the mark and the feature: if it moves up then use the slider on the right to bring it down or vice versa. Figure 10. Setting the eucentric position: (i) set the working distance as 10mm (ii) increase the magnification to 10kX, focus on an identifiable feature, (iii) link the stage, (iv) change the tilt angle gradually, center the feature using the slider 2. Iterate this procedure for 10, 20, 30 and 52 (Figure 11). Then tilt the stage back to 0, the feature should come back to its original position. 9

10 Figure 11. Stage tilt and presentation of a feature High Resolution I-Beam Imaging 1. Check the eucentric height (working distance = 10mm), tilt the stage to On the first (e-beam) quadrant, focus on the center of interest at 5kX magnification. 3. On the second (i-beam) quadrant, set the voltage to 30kV and current to 30pA. 4. Ion beam is damaging to your sample, you may follow these steps to focus on your sample: i. Instead of continuous imaging, highlight the second (i-beam) quad and use take snapshot option under Image Acquisition button at the top panel. Adjust the brightness/contrast and focus and take snapshot between iterations. ii. Or start with an area nearby of the point of interest and use the reduced area for adjustments. Set the reduced area on a feature, unpause the i-beam and adjust focus, brightness and contrast in the reduced area. Act fast! iii. Or change the direction of the beam, using beam shift panel, on the <Beam Control> tab, shift the beam, do the adjustments and bring to original beam position by right clicking on the panel and zero. 5. When you take a snapshot, if the magnifications are different in e-beam and i- beam screens, you may couple magnifications on the Beam Control tab, this will take the active screen magnification as the basis. 10

11 Pt-Deposition with e-beam 1. Before deposition Pt on a feature, make sure the GIS is on. 2. Pick the feature, set magnification (example: 3500X) and focus 3. Change the standard mode to analytical mode. Wait until it settles and link the stage (in first (e-beam ) quadrant). Analytical mode: In this mode the largest (1000 µm) aperture is automatically selected and the beam current is limited to a range. It is used for, imaging and mapping at currents above 4.0 na, and precise beam current control and high beam current stability. 4. Insert the Pt needle by clicking the green square on <Patterning> tab,. This will insert the Pt-needle, avoid making z-movements when the needle is in, and small movements on x and y directions. Inserting the needle will change the B/C. 5. On the Patterning tab (Figure 12): i. select the pattern as rectangular and ii. draw the rectangle (yellow at first), iii. from the applications menu, select Pt e-dep structures make sure the pattern turns into green. iv. Adjust the size of the area by typing, set the z to 100nm, the time required to complete the process is listed on this tab. 11

12 Figure 12. Pt-deposition in the Analytical Mode: (i) On the patterning tab, select the rectangular pattern, (ii) draw the area to be deposited, (iii) select the appropriate application and adjust the size. 6. Click on the start patterning button at the top panel. During the process, the active quad (e-beam) turns into green. 7. When the deposition is completed, first take the needle out by clicking the green square on the Gas Injection. 8. Delete the pattern and switch to Standard Mode. 9. Unpause the beam, you may see the Pt-deposited surface. Pt-Deposition with i-beam The Pt-deposition with e-beam Analytical mode is to protect the feature even during the Pt-deposition with i-beam. The i-beam is very damaging to surface, hence Pt-deposition with e-beam adds a protective cover. Follow the instructions below: 12

13 1. Focus on the point of interest, adjust magnification and link the stage on the first quad (e-beam), activate the second quad (i-beam) and adjust the accelerating voltage and current to 30 kv and 30 pa, respectively. 2. Check the eucentric point (on the point of interest), and tilt the stage to Insert the Pt needle by clicking the green square on <Patterning> tab,. This will insert the Pt-needle, avoid making z-movements when the needle is in, and small movements on x and y directions. Inserting the needle will change the B/C. 4. Activate the i-beam quad and take a snapshot by Image Acquisition button, you may even see the Pt-needle inserted. Select rectangular pattern and draw. Then select the Pt-dep from the applications menu, adjust the size of the pattern. (Figure 13) Figure 13. Pt-deposition: (i) On the patterning tab, select the rectangular pattern, (ii) draw the area to be deposited, (iii) select the appropriate application and adjust the size. 5. The time given is calculated based on the accelerating voltage and current settings (30 kv and 30pA), although these setting might be good for imaging purposes, 13

14 not sufficient for Pt-deposition. Increasing the current will yield faster deposition, however mills/damages the surface as well. Rule of thumb: The trade off between the milling and deposition: Calculate the area (x = 20 µm, y = 10 µm) as 200 µm2, multiply this by 6, 1200 µm2, this corresponds to the maximum current that should be used in terms of pa. In this case, the maximum current should be 1200 pa = 1.2 na. 6. Change the current to 1 na, control the time required. This will shift the image, so take a snapshot, if necessary correctly place your pattern. 7. Simultaneously, you may watch and record the deposition process via e-beam imaging. This feature ispi- is available at the <Patterning> tab,. Depending on the time interval, the e-beam quad will be refreshed. (Figure 14) Figure 14. Pt-deposition and simultaneous imaging with e-beam 8. When the deposition is completed, first take the needle out by clicking the green square on the Gas Injection and delete the pattern. 9. Switch to e-beam quad for imaging. Cross-Sectioning Cross sections are cut in a stair step fashion to allow the exposed layers to be seen with the electron beam when the stage is tilted to 52. To section a sample, you may protect the feature by Pt-deposition, or you may directly cross section the sample. 1. Focus on the point of interest, adjust magnification and link the stage on the first quad (e-beam), adjust the accelerating voltage and spot size to 30 kv and 5, respectively. 14

15 2. Check the eucentricity of the feature. The working distance = 10mm is the eucentric point. 3. Activate the second quadrant (i-beam), adjust the accelerating voltage and current to 30 kv and 30 pa, respectively. 4. If needed, deposit Pt on the surface, refer to previous sections for instructions. (F2 F3 F4) Figure 15. The progress of Pt-deposition on the surface 5. Focus on the point of interest in the second quadrant (i-beam) and go to <Patterning> tab,. From the drop-down list, select the regular cross section. And draw the pattern on the point of interest. Select the application as Si-multipass New, (or choose the application close to your sample from the list). Adjust the size of the area to be sectioned. Make sure the y-size is at least 2 times higher than the x-size. Set the z to 5 um. 6. Notice the total time, which is based on the current, 30 pa. Adjust the current to 15 na and check the time. Take a snapshot to check the final position of the pattern. 7. Set the imaging parameters in the first quadrant (e-beam), set ispi parameters on the <Patterning> tab. 8. Start the process with the Start Pattern button,. 15

16 Figure 16. Cross-sectioning process (i) ispi allows to view the progress, (ii) The sectioning on the second quadrant starts from the bottom and moves to top, its size is adjusted 9. Once the process in finished, change the current back to imaging current, 10 pa. Delete the pattern. 10. You may now activate the first quadrant (e-beam) and save images. 11. To image the cross-section with the i-beam, tilt the stage back to Rotate the stage 180 (compucentric rotation): a. Use the short cut key F12 b. Type in the rotation on the <Navigation> tab. 13. Change the scan rotation by 180, using the short cut key Shift-F12. Cleaning Cross-section 1. To minimize the damage and expose the cross-section, one fine-tuning is to clean the cross-section. 2. On the same spot, increase the magnification. On the <Patterning> tab, select the Cleaning Cross Section pattern and place the pattern, just to cover the wall of the cross-section. 3. Select Si-ccs New as application, adjust the size of the pattern and set the depth as the same you used in cross-sectioning. 4. The purpose is to clean the wall while minimizing the damage on the surface, therefore set the current to 1/5 (or less) of the current you used for cross-sectioning. (1nA) 5. You may iterate the procedure for lower currents for multiple times and increase the tilt angle to 53. (0.5 na, and 100 pa in this example) 6. After the process is completed, change the current to imaging current. 7. You may now activate the first quad (e-beam) and save images. 8. To image the cross-section with the i-beam, tilt the stage back to Rotate the stage 180 : a. Use the short cut key F12 16

17 b. Type in the rotation on the <Navigation> tab. 10. Change the scan rotation by 180, using the short cut key Shift-F12. System Shut-Down 1. Retract any inserted detectors. 2. Turn off the beams, on the Beam Control tab, either click on SLEEP button (or click on BEAM ON button for the beams you have used). 3. Return the stage to home position. The home stage option is under Stage > Home stage on the top menu. 4. Click on VENT button to remove your sample, wait until the chamber is completely vented (the pump will stop). 5. After removing the sample, hit PUMP again and leave the chamber in vacuum. 6. Log Off the system after the chamber vacuum is reached and the icon is fully green. 7. Log out from the user tracker.. 8. Record your time and experiment specifications in the logbook. 17