This procedure will allow you to determine the electron beam diameter diameter on scanning auger electron spectrometers using the line scan feature of AugerMap software and the magnification standard (or, a straight edged sample). Although written for scanning auger electron spectrometer systems, the principle is the same for SEMs – scanning electron microscopes – measure the slope across an edge at a known magnification.
1. Insert the beam size standard into the system and perform an elastic peak alignment on the top surface of the sample to ensure that the sample is at the correct Z position with respect to the analyzer. Do not tilt the sample.
- Set elastic peak
2. Next, change the beam voltage to 10KV and adjust the electron gun parameters for a good image at 5000X or higher magnification.
3. if so equipped, adjust the Condenser and Objective steering plates for minimum movement. (If an SEM, rock the lenses).
4. Ensure that the image is in the best possible focus.
5. Lower the magnification to the lowest possible setting and move the beam size standard to the center hole to find the grid and adjust the Z position until the grid is in focus. The sample is now at the correct focal point on the analyzer. This is a good trick that you can use on any scanning auger system – if you first set the elastic peak and then the focus, as long as you mechanically bring the sample back into focus after moving to a different location on the sample (and do not change the focus knob or settings in the software), the sample to analyzer distance is still correct.
6. Set the magnification to 100KX and fine-tune the focus and stigmators as required. The sample can be moved on either the X or Y axis until you are able to line up on one grid line.
7. Obtain an SED video map and use the quantization feature if necessary.
8. Select the line scan feature in AugerMap and draw a line horizontally across the grid line.
9. For AugerMap1, Add region – SED line.
10. Select Video input; point one ms per step, number of sweeps one, and resolution 256 points per line. For AugerMap II, select SED video map.
11. Acquire the line scan.
12. After the line scan is completed it will show a display of signal intensity on the Y-axis vs. distance scanned on the X-axis. At 100KX magnification, this distance is 1uM, or, 10,000 angstroms. By determining the slope of the beam diameter as it crosses the edge of the sample, the beam diameter can be determined.
13. Print out the line scan and use a ruler to determine the top 20% and bottom 20% of the line scan. Draw a line across the top 20% and bottom 20% of the line scan.
14. Next, draw a line on the slope of the beam diameter as it drops down or up between the 20% lines.
15. Determine the distance between the slope of the line at the top of the scan and the bottom of the scan. This distance represents the beam diameter in relationship to the full scan (10,000 angstroms at 100KX).
16. The example below shows in detail how this measurement is calculated.
Perform this measurement anytime that you wish to know the size of the electron beam diameter for any given set of conditions. If the beam size is too large to see one grid line, you can reduce the magnification to 50KX, in which case full scale on the X-axis would be equal to 20,000 angstroms.