Scanning Electron Microscopy

From LPDwiki

Before Starting SEM

1. Two types of controllers

1a. SUPPORT PC → Access by pressing #2 on the control box → All image files are there + Badger

1b. CONTROL PC → Access by pressing #1 on the control box → Access XT Microscope Server

2. XT Microscope Server Login

2a. First, login to Badger and enable the machine → Username, Password (login info is different for different users)

2b. Then, press 1 and go to the Control PC.

3. Is the instrument ready to use?

3a. The following parameters need to be noted down and remembered before starting:

  • Chamber Pressure: 10-6 - 10-5 mbar
  • Gun Pressure: 10-9 mbar
  • Emission Pressure: 10% of whatever was recorded by previous user
  • Column bar has to be green, as it means that the source is ready (BEAM CONTROL).
  • Dwell time: 2 x 50 ns
  • Frames: 2 frames
  • Resolution: 1024 x 884
  • If vacuum icon is green it means the chamber is under high vacuum. If it is orange, it is not under high vacuum, but it doesn’t have to mean it is atmospheric pressure (not vented).
  • Note, tip-pole piece is the electron source and on the right is ETD detector.
  • Zero the stage after checking parameters → ctrl + 0.
* If the values above are off, call CNM2 support.
* If Application Status comes out, call CNM2 support.
* If SEM chamber is open, call CNM2 support.

Running SEM

ESC key is to abort any process.

1. Vent → YES → Load the samples

  • Aperture Strip is usually set to 5, but one can change it for different resolutions.
  • Venting is usually done when there is no more sound (this is for complete venting, but hissing sound is the signal that the instrument is ready).

2. Sample preparation

2a. Tighten the two screws on top of the sample (try to avoid scratching and breaking the sample while loading onto SEM sample holder).

3. Opening and closing the instrument

3a. Look at CCD camera when opening/closing the chamber to make sure the tip doesn’t get damaged.

3b. Load the sample and then close the door. Hold the door with a finger and press PUMP. Hold the finger until click sound. (Instrument will make a weird sound).

4. Make sure High Vacuum Mode is always on. It is under Detectors Icon.

5. Check that ETD camera (top left screen) has: Secondary Electrons selected and Grid Voltage of 250 W.

6. Check Measurement Annotation under the Processing Icon (need to get straight blue line).

6a. Contrast: 1.0

6b. Brightness: 0.0

6c. Gamma: 1.0

6d. Histogram: left is dark and right is bright (Histogram needs to a bell curve to avoid losing any data to too bright or too dark spots).

7. Click on CCD camera, hold the scroll on mouse and move the stage to and from 5 mm mark. Make sure to UNPAUSE the screen first (F6 or PAUSE button), otherwise you might break the tip!

8. Start with spot: 2.0 (This is size of the beam) under Beam Control.

9. High voltage: 10.0 kV (drop the voltage to 5.0 kV if there is too much charge, usually for insulating samples).

10. Turn on the beam

10a. Column → HV

11. Change the Magnification to see the sample (Big Knobs). It is better to image samples close to the clips, because that is more conductive area.

  • Make sure to get the aperture (circle around the sample) out of the imaging screen before doing any alignments and/or adjustments → Zoom In.
  • It is always good to start working with some scratch place.

12. Change the Brightness.

12a. Set Videoscope ON or F3.

12b. Change the Brightness (position) so that the signal under Processing is across the middle line.

12c. Change the Contrast for the Amplitude.

12d. Processing → Histogram should be a bell curve, but with no spikes on the side, because that means some data is being lost.

12e. Play with Contrast and Brightness to get rid of spikes. When done, press F3 to get rid of it.

13. To move the stage, you can double click on the point to be moved to. OR: Press and hold the mouse wheel to move around.

14. Now, find a spot with a lot contrast, the best are small dark circular spots. This is to do alignment properly. Then go to the Full Screen by pressing F5. Change the focus if it is blurry.

15. Set magnification to x1 000 and then adjust the focus. After that go to x2 000, x4 000 all the way up to x16 000 before doing any other alignments. Focus/Coarse at each step.

16. When the background starts moving, it means that the Stigmator needs to be adjusted.

  • Move X and Y knobs to stabilize it. The strikes go either left or right. Find the middle and play with focus to stabilize it all.

17. Make sure to stabilize Lens Modulator as well.

17a. Press Modulator. Play with Lens Align until it stabilizes.

17b. If it is very unstable, change to Coarse (right click on the Lens Align), stabilize and then go back to Fine.

17c. If you get lost when stabilizing and it seems like nothing is working, than just Zero by right clicking on Lens Align.

18. Once everything is aligned, Link Z to FWD to get aligned parameters to the stage parameters.

  • Make sure to exit the fullscreen (F5) and that you can see CCD camera not to damage the tip!
  • Make sure CCD camera z coordinate is 5 mm. Refocus to make image clear again if there are any changes here.

19. Use Immersion Mode for the features that are less than 1 µm. Change the focus if it is too bright. Go slowly with Focus to refocus it back.

  • Note: Switch to Mode 2, Immersion Mode, at magnifications > x40 000.
  • Play with Coarse again until reaching x100 000 magnification.

20. Align the sample at x3 Magnification of the magnification at which the image will be taken.

21. Before saving the image check Histogram. Adjust Contrast and Brightness to get the bell curve before saving the image. Go for lower Contrast and higher Brightness. Focus at the end.

22. Use F2 to take the image. The first image freezes, but it will unfreeze and the Save Box will pop up. Do the scan at 24 µs rate.

23. Save the image with Databar ON and Overlayed Graphics ON. Save everything is jpeg. High quality images are obtained by decreasing the speed the of scan, e.g. 45 µs.

24. Take more images at other points.

24a. Make sure to go to Field Free 1 mode before finding another spot.

24b. Zoom out, find the center.

24c. Zoom in, e.g. x100 000 and go back to Immersion mode. Live view is F6.

24d. Focus and Image with F2.

  • Note: To make less noise at higher magnifications, change Integrate to more frames.

Shutting Down

1. Switch back to mode 1 (Field-free instead of Immersion mode).

2. Switch the beam off by pressing HV.

3. After hissing noise stop, press Vent. Icon changes to orange; there is a pressure increase.

4. Take the sample out.

5. Pump the chamber while holding the door again.

6. Home the stage. (Stage → Home Stage)

7. Fill out the Booklet.

8. Log off and use Black button to go to Support PC. Make sure the pressure goes down, pressure chamber icon becomes green.

9. Badger → Equipment Actions → Disable the tool.

  • Note: If you ever press Degas by accident, that is fine. Degas gets rid of hysteresis and one might need to change Focus just a little bit later.