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PM sequence on XPS and AES systems

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Performing regular Preventive Maintenance on surface analysis systems such as X-ray Photo Electron spectrometers (XPS) and Auger Electron spectrometers (AES) is a very important step in keeping the systems functioning properly and reliably. But performing the necessary steps in the correct PM sequence will make sure that you maximize the use of your time.    Below are the PM sequences that I use when performing preventive maintenance on XPS and AES surface analysis systems.

 5400/5500/5600 System Maintenance Guide

 PM Procedure – OPTICS

  1. Discuss System performance and issues with system operator prior to service visit.
  2. Inspect system, note base vacuum. Test TSP filaments.
  3. Make sure that you have all necessary parts for the maintenance. If you are missing anything, order it before proceeding. For maximum efficiency, you will perform vacuum maintenance first as you can inspect and clean the electronics during the system bake out and cool down.
  4. Prepare to vent the system by shutting down all filaments and voltages to the ion guns, X-ray sources and neutralizer.
  5. Turn off the DIGIII and Boostivac. Let the system cool for 10 minutes.
  6. While the system is cooling, prepare a work area for optics maintenance.
  7. Vent the system (make sure that the turbo pump(s) are on to prevent oil vapors from back-filling during the vent process). After the system is up to air, turn off the turbo pump(s).
  8. Remove the X-ray source(s) from the chamber and inspect the filaments, window, football ceramic and anode. Replace parts as needed.
  9. Remove the ionizer from the Ion gun and inspect the ionizer. Replace if needed.
  10. Remove the Ion Gauge and inspect the filaments. Replace if needed.
  11. Replace TSP filaments as needed.
  12. If the 04-085/090 Neutralizer filament needs to be replaced, remove the neutralizer and replace the filament. It should be replaced every 4 years of normal usage.
  13. If channel plates or electron multiplier needs to be replaced, remove the 6″ flange on the SCA and replace the multiplier. This typically is replaced every 3 to 5 years depending on usage.
  14. Inspect the ion gun ionizer and replace if needed.
  15. Pump down the system.
  16. Start the ion pumps.
  17. Prepare the system for bake out – NOTE: Remove the microscope by unscrewing the locking screw. Do not remove the lower portion to make it easier to re-align the microscope after the bake out.
  18. Once the system reaches at least the mid 10-7 Torr range, then the system can be baked for 12 hours.

PM Procedure – ELECTRONICS

 

  1. Make sure the card rack power is off and visually inspect all electronic cards and units.
  2. Clean all edge connectors with alcohol and q tips (not an eraser).
  3. Replace as needed any marginal capacitors, resistors or transistors.
  4. Replace all neon bulbs.
  5. Replace CM85 bulbs in EMU unit as needed. Note that if the Vacuum Console bulb needs to be replaced that the entire system needs to be shut down first.
  6. Clean electronic card rack filters.
  7. Inspect 16-020 or 16-050 heat exchanger for dust on radiator, clean as needed.

 

System Outgas Procedure

  1. With the card rack power off and all electronic units off as well (except for the ion pumps, DIGIII and turbo pumps), re-connect all system cables.
  2. Reconnect the microscope.
  3. Load the slotted silver sample into the system.
  4. Turn on the card rack power and the power to the Ion gun control and X-ray source control.
  5. Load AugerScan software.
  6. Turn on the ion gun control and outgas the filament slowly to 25mA and 2 to 3kV. Do not sputter the slotted silver sample at this time.
  7. Out gas the X-ray source filaments and condition the anodes to 16.5kV slowly.
  8. Lightly sputter the slotted silver sample.
  9. Find the focal point of the SCA using the slotted silver sample and align the microscope to that point.
  10. Load a piece of Cu and AU side by side an calibrate the pass energy tracking and then the XPS energy linearity.

 Calibration

Calibration sequence:

  1. Calibrate Small Spot on Slotted Silver Sample
  2. Calibrate Au and Cu peak linearity:
    • * Pass Energy Tracking
    • * Au 84.0
    • * Cu 932.67
  3. Align ion gun to focal point. – Load a piece of TaO5 with an X scribed into it. Put the X at the focal point of the microscope and then burn a hole into the TaO5 with no raster. Adjust the ion source as needed to center the sputter crater in the middle of the X.

 Specifications
Refer to the counts/resolution Specifications for the specific system type that you are testing. In general, if the resolution spec (less than .8eV FWHM on clean silver) can be met then the system will be performing properly in all pass energies.

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595, 600 and 660 PM Sequence

Following the sequence listed below will maximize the use of your time when calibrating and documenting system performance during a PM or installation of a 595, 600 or 660 scanning Auger system.

Perform optics checks (CMA filament, SED and CMA electron multipliers, TSP filaments, Ion gun ionizer and ion gauge filaments) and replace parts as needed. Bake out system.

Perform electronics inspection. Clean air filters if applicable.

Calibration

  1. Load a sample with SiO2 and Cu side by side.
  2. Adjust the elastic peak on the SiO2 with the sample at 60 degrees with respect to the analyzer. That is 30 degrees on a 600 or 660 specimen stage.
  3. Align the ion gun to the center of the SiO2.
  4. Move to a fresh spot of SiO2 and lightly sputter the sample with a raster of 2 X 2.
  5. Change the sample angle to perpendicular to the analyzer. That is Zero degrees on a 600 or 660 specimen stage.
  6. Select point mode and acquire an elastic peak.
  7. Adjust the Z axis for maximum counts.
  8. Adjust the collector housing (600 or 660 only) for max counts and best peak shape. This will be slightly non-Gaussian.
  9. Readjust the Z axis for max counts. This does not need to be exactly 3kV.
  10. Check the analyzer resolution for 18 eV between the differentiated and balanced peaks of the elastic peak at 3kV (or 12eV at 2kV on a 595).
  11. Adjust the resolution knob if needed to obtain 18eV differentiated and set the resolution knob to indicate .6%.
  12. Recheck the Z position and collector housing adjustment to ensure that the sample is at maximum counts and 18ev differentiated.
  13. Move to the copper sample, set the tilt to 60 degrees with respect to the analyzer and adjust the elastic peak for max counts with the scanning set to 10kX magnification (to eliminate topography effects).
  14. Sputter clean the copper until there is no carbon present.
  15. Re-check the elastic peak to ensure it is at maximum counts and 18eV when differentiated.
  16. Check the AES energy position of the 914 Cu peak (917 differentiated). Note: The earlier handbooks indicate 920 differentiated, the newer handbooks indicate 922 eV differentiated, and the correct position is 917 differentiated for the 595, 600 and 660 analyzers due to the magnetic lenses. However, you can set it to whatever the system operator prefers. We recommend 917eV.
  17. If the Cu peak does not come in at 917eV, then adjust the AES scale factor until the peak comes it at 917eV differentiated (or what the system operator prefers).
  18. Acquire another elastic peak but DO NOT MOVE THE SAMPLE. If the peak does not come in at 3kV (2kV for a 595), then adjust R108 in the 20-610 HV supply until the elastic peak is at 3kV.
  19. Document result (3kV elastic peak at .6% resolution).
  20. Acquire a survey from 30 to 1030 Ev and Document result (AES energy calibration). Annotate the Scale Factor and Cu low and high energy positions.
  21. Verify that low energy copper peak and high energy copper peak are a ratio of approximately 1:1.
  22. Set beam voltage to 10kV and with the objective aperture set to the largest; adjust the COND and filament housing position for maximum target current.
  23. Adjust emission current for maximum target current. Document result (max beam current). Specification is greater than 10uA at 10kV.
  24. Set the aperture to the number 2 aperture and the COND to about 45. Set the beam current to 10nA. Refocus the image, set back to 10kX magnification.
  25. Acquire a survey from 900 to 960 eV, 1 eV per step, 50mS per point, and 5 sweeps.
  26. Calculate the signal to noise (P-B/ B). Document result (10nA S: N), specification is greater than 250:1, near 300 is typical.
  27. Set the beam current to 1nA (COND to about 50) and acquire the survey again.
  28. Calculate the signal to noise (P-B/ B). Document result (1nA S: N), specification is greater than 80:1, near 100 is typical.
  29. Move back to the SiO2 and reset the beam voltage to 3kv, COND to about 40.
  30. Acquire an elastic peak and recheck the alignment of the ion gun. Document result (ion gun aligned).
  31. Acquire a depth profile on the SiO2 and verify that the sputter rate is at least 300 angstroms per minute at 4kV with no raster. Note that due to the ion current density, the sputter rate will be about the same with the 11-065 COND set to 5.0 (smallest spot) or 3.4 (maximum ion beam current). Document result (ion sputter rate check).
  32. Remove the SiO2 and Cu sample and install the 1500 LPI magnification standard.
  33. Adjust the elastic peak on the edge of the holder.
  34. Increase the beam voltage to 10kV and the COND to about 50. Adjust the electron gun parameters for the best image possible at 5000X and then reduce the magnification to 500X.
  35. Move the sample until the grid is in the center of the image and bring the stage Z up until it is in focus. Note: Do not change the OBJ or fine focus on the electron gun. The idea is to bring the sample to the focal point of the CMA.
  36. Run up the magnification until there is only one grid visible and calibrate the magnification for 16.7 uM. Document result (magnification calibration).
  37. Set the beam current to .05nA (COND near 60) and increase the magnification to 20kX and move to where one grid is being scanned.   Adjust the COND and OBJ Steering for minimum image movement. Turn off turbo pump to reduce vibration.
  38. Set the magnification to 99,999X and acquire a video line scan. Document the results. (Beam size check). Specification is less than 350 angstroms at 10KV.

 

Summary of checks and calibrations

Elastic Peak

Collector Housing

Cu Energy Calibration

Maximum Beam Current

Cu signal to noise at 10nA and 1nA

Ion gun alignment

Ion gun sputter rate

Magnification

Beam Size

 

Filament Housing Cleaning Procedure

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25-120A Filament Housing Cleaning Procedure

Overview

The filament housing contains two micrometers which are used to position the filament for maximum beam current. The filament is mounted in a ceramic that is attached to a bellows which is supported by an aluminum ring that slides against a plate. The ring and the plate are lubricated and when the lubrication dries out from baking, the ring becomes scored and the filament housing “sticks”. This procedure explains how to disassemble the filament housing and repair this problem.

  1. Vent the system. This removes all tension from the filament bellows.
  2. Remove the two filament micrometers.
  3. Removed the two spring housings. CAUTION! The springs are very strong, remove the top and bottom screws first and then “walk” out the spring with the two side screws.
  4. Remove the top screws from the filament housing.
  5. Remove the top of the filament housing.
  6. Remove the micrometer levers. Note the positions for re-assembly.
  7. Remove the screws that connect the aluminum ring to the ceramic.
  8. Remove the lower filament housing Bristol screws.
  9. Carefully lift up the lower filament housing.
  10. Sand down the surfaces of the aluminum ring and plate.
  11. Lubricate the aluminum ring and plate with C5A (copper based anti-seize lubricant).
  12. Reassemble in reverse order.

If you have questions about this procedure, please contact us or post a comment.

Measuring electron beam diameter

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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

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.

auger-map-2-sed-dialog-box

AugerMap 2 SED dialog box

 

 

 

 

 

auger-map-sed-dialog-box

Auger Map version 1 SED dialog box

 

 

 

 

 

 

 

 

 

 

 

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.

beam-size-measurement

Beam Size Measurement

 

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.