Tag Archives: X-ray photoelectron spectroscopy

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

 

32-100 electron multiplier supply digital mode

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The model 32-100 electron multiplier supply is used on older Physical Electronics Auger electron spectroscopy and X-ray photoelectron spectroscopy surface analysis systems to control the electron multiplier voltage.

When using the 32-100 electron multiplier supply in the digital mode (the software automatically sets the electron multiplier voltage)  the auto-ems box in the Auger Scan software AES electron multiplier properties dialog box needs to be checked, and the CMA multiplier switch on the front panel of the 32-100 must be set to digital.

But what if the 32-100 still does not work in the digital mode?  In that case, there may be a problem with one of the digital ICs.  The following procedure explains how to try and repair this problem.

  1. Turn off the 32-100 and remove the cover.
  2. Most 32-100s have three ICs for the SED digital side of the control which are not used. You can move those ICs over to the CMA side of the control and see if that solves the problem.
  3. Remove ICs U2, U4 and U6. These are the CMA digital ICs. Then, move over U3, U5 and U7 from the SED side if those chips are available. If they are missing, then you will need to order some of those ICs from Digikey, Newark or RBD Instruments. U2 and U4 are 74LS174s and U6 is an AD7521.
  4. If you did have those ICs and that did not solve the problem, then it most likely means that one of the encoder circuit ICs are defective. Those are U16 (74123) and U1 (AM25LS2538). RBD Instruments provides these parts.
  5. You do not need to replace the SED digital ICs as they are not used.

It is assumed that the 32-100 is working in the analog mode. If the 32-100 is not working in the analog mode it will not work in the digital mode either.

Refer to the pictures below for the locations of the ICs on the 32-100 motherboard.

Note that the switch positions need to be set as shown below.

 

32100-switch-positions

32100-switch-positions

 

If you need further help troubleshooting your 32-100 electron multiplier supply please contact RBD Instruments dot com

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PHI Optics Repair Guidelines

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This document contains information about optics repair methods, procedures and tricks that are useful when working on older PHI optics units such as cylindrical mirror analyzers, x-ray photoelectron spectrometers and sputter ion sources.

General Optics Guidelines.

  1. Clean all tools with isopropanol or methanol and also degauss them if possible. Most customers have degaussing coils which came with their system. If not, RBD can provide them.
  2. Always use gloves when working with optics.  This is to keep oils from your fingers from contaminating the optics.
  3. Maximize space between all high voltage wires and ground to prevent arcing.
  4. Avoid sharp points on all connections to prevent arcing.
  5. When ever possible, cover all high voltage wires with ceramic tubing, ceramic beads or Teflon tubing. If you can’t do that, then make sure all HV wires have gentle bends and no sharp bends.  Sharp bends, just like sharp points, can increase the chance of arcing.
  6. Tighten all screws securely, especially if the unit needs to be shipped after a repair.  Vibration from shipping can cause optics to loosen up and become damaged.
  7. Degauss the analyzer several times during the re-assembly process, especially when the magnetic shields go back on.

Analyzers.

Single pass CMA (cylindrical mirror analyzer).

The PHI single pass CMA is the most common type of Auger (AES) analyzer in the surface analysis industry. It is a very simple and mostly reliable device.  Double Pass CMAs are essentially two single pass CMAs stacked on top of each other to increase energy resolution which allows for the acquisition of X-ray Photoelectron spectroscopy (XPS, or ESCA) data.

To maintain optimum performance, analyzers need to be cleaned periodically.  Depending on usage, vacuum conditions and amount of sputtering, this could be anywhere from 2 years to 20 years.  Expendable items such as filaments, electron multipliers and grids need to be changed on more regular basis.

PHI CMAs that RBD services:

Model Number Description Specifications Filament type Multiplier type
10-150 TFA 100 uM beam size C75010RP 4839RE
10-155 TFA 100 uM beam size C75010RP 4839RE
15-110 Scanning 5uM beam size C75010RP 4731GRE
15-110A Scanning 3uM beam size C75010RP 4731GRE
15-110B Scanning 1uM beam size C75010RP 4731GRE
15-255G Double pass CMA 100uM beam size C75010RP 4731GRE
25-110 Scanning 2000Ǻ beam size LAB6590RE 4831GRE
25-120 Scanning 500Ǻ beam size LAB6595RE 4831GRE
25-120A Scanning 350Ǻ beam size LAB6600RE 4831GRE
25-250 Double pass CMA 100uM beam size C75010RP 4731GRE
25-260 Double pass CMA with Scanning 1uM beam size C75010RP 4731GRE
25-270 Double pass CMA with Scanning <1uM beam size C75010RP 4731GRE

CMA analyzers have many things in common. For example, all CMAs have:

  • Inner cylinders with grids
  • Outer cylinders
  • Conical and flat terminating ceramics
  • Electron guns
  • Ceramic feed-throughs
  • High voltage insulating ceramics
  • Copper and tantalum wire
  • Coupling connectors
  • Set screws
  • Magnetic shields

General Analyzer Tips

Be very careful when removing and replacing the conical ceramic as it can chip and break easily. Replacements cost is $2K to $4K.

When replacing the conical ceramic, rotate it slightly. If the conical ceramic appears to be loose remove it and place some copper shims on the lip if the inner cylinder to ensure a solid electrical contact. If the conical ceramic does not make a good electrical contact, the background counts in the data will increase dramatically above 800 eV or so, resulting is poor data.

Ensure that all electron gun ceramics and lenses seat properly before tightening. This ensures that the electron gun will be co-axial with the center of the CMA.  If the electron gun is not centered, it will be off-axis resulting in a poor elastic peak shape and low Auger signal.

Use tantalum wire for deflection leads.  It is more flexible than copper and will last longer before it breaks.

Use .020″ copper wire or thicker for filament leads.  .015″ wire will not provide sufficient current to the filament and you will not be able to get any emission from the filament.

Measure the resistive of the flat terminating ceramic and conical ceramic before you re-assemble the analyzer.  Note the values so that you can determine if they are making proper electrical connection after the conical ceramic is replaced. Example: The flat ceramic is 4 M ohms and the conical ceramic is 1 M ohms.  If the conical is not making contact, the resistance from the outer cylinder to ground will be 4 M ohms.  If only the conical ceramic is making contact but the flat is not, the resistance from the outer cylinder to ground will be 1 M ohms.   If they both are making good electrical contact, the resistance will be 750KW.

The outer cylinder is called VM (for voltage modulation) on most CMA analyzers.  On double pass CMAs such as the 15-255G and 25-260/270, it is called OC (for outer cylinder).

VM and OC resistance checks.

Model Number Resistance check
10-150 VM to ground = 3 to 3.2 M ohms
10-155 VM to ground = 3 to 3.2 M ohms
15-110 VM to ground = .6 to .8 M ohms
15-110A VM to ground = .6 to .8 M ohms
15-110B VM to ground = .6 to .8 M ohms
15-255G IC to OC = .6 to .8 M ohms       IC and OC to ground = open
25-110 VM to ground = 3 M ohms
25-120 VM to ground = 3 M ohms
25-120A VM to ground = 3 M ohms
25-250, 25-260, 25-270 IC to OC = .6 to .8 M ohmsIC and OC to ground = open GR to ground = open

Tip: If measuring on a system, make sure that the electron gun is off or the electrons coming into the front of the analyzer will give you a false reading.

10-155 electron gun detail

590 Filament Replacement Procedure

  1. Remove the magnetic shield (4 screws).
  2. Carefully remove the conical ceramic ring (4 flat head screws) and remove the conical ceramic.
  3. Remove the outer cylinder (1 screw), careful not to force it. If necessary, use a heat gun to loosen it up.
  4. Separate all of the wires in the bottom of the analyzer using 2 needle nose pliers or tweezers.  Be careful not to stress the wires.  Position the wires so that you can easily remember where the go back.  In the case of the F1 and F2 wires, this is easy. For the DEFL/STIG wires, position the wires as upper right and upper left, lower right and lower left.
  5. Loosen the 4 spline set screws on the top of the inner cylinder by 1 turn CCW.
  6. Remove all but one of the eight screws around the middle of the inner cylinder.
  7. Remove the upper inner cylinder grid cap (4 screws).
  8. Holding on to the nose of the electron gun, remove the final screw at the middle of the inner cylinder.
  9. Carefully pull the electron gun up and out of the inner cylinder.  Be careful not to stress any of the wire connectors.
  10. Place the electron gun on a sheet of aluminum foil.
  11. Loosen the bottom cap of the electron gun (4 screws and 4 set screws)
  12. Carefully slide the bottom cap down the ceramics for about 2”, enough room to get at the filament.
  13. Remove the filament assembly (4 cap screws, 2 splines connecting the filament wires).
  14. Install the new filament assembly, and reverse all of the above steps.

General tips:

Clean and demagnetize all of your tools.

Place all removed parts on a clean work area covered with Aluminum foil.

If possible, dust off all parts with nitrogen as you re-assemble them.

Never force any part that doesn’t want to go.

You can use methanol as a lubricate if screws don’t move easily.

 15-110 Analyzer Burn-In Procedure (also for the 560 AND 570 ESCA analyzers)

  1. First, bake system after installation.  If that is not possible, bake out just the analyzer using heat tape.   200 degrees Celsius for 6 to 8 hours.
  2. Allow the analyzer to cool down.
  3. Set the beam voltage to 500 volts and the emission know fully CW. Slowly turn up the filament current on the 11-045 until you have  .1 to .2 mA of emission current (about 6 to seven turns on the filament knob).
  4. Very slowly,  (over a period of 1 to 2 hours) bring the filament up to 2mA of emission current.
  5. Next, slowly bring the beam voltage up to 2kV (about 30 minutes from 500 volts).
  6. Set the condenser on the 11-045 to maximum and do an elastic peak alignment.
  7. Slowly increase the multiplier voltage until a peak is just visible.
  8. Leave the multiplier voltage at this setting for 6 hours or more.
  9. After the multiplier burn-in procedure is complete, slowly increase the beam voltage to the normal setting.

Note:  The higher you operate the beam voltage, the slower you need to out gas it.  Typically, you can go from 2kV to 5kV in 2 or 3 hours. 5kV to 8kV takes an additional 4 to 6 hours. Once conditioned, you can go up to that beam voltage quickly.

15-255G Filament Change Procedure

Use gloves, de-magnetize all tools and clean all tools with Isopropanol.

  1. Set analyzer on stand or use manuals and support analyzer on handles, facing up.
  2. Remove outer magnetic shield (4 screws)
  3. Remove inner magnetic shield (4 screws)
  4. Carefully remove conical ceramic
  5. Lift upper outer cylinder up and set aside on clean aluminum foil.
  6. Carefully lift inner cylinder up and off of the electron gun assembly. Note: If the inner cylinder does not move freely, use a heat gun to expand the inner cylinder so that it will slide off. Do not force it! Be careful not to damage the grids.
  7. Look at the 10-155 electron gun detail to familiarize yourself with the electron gun assembly.  The 15-255G has basically the same electron gun as in the 10-155.
  8. Remove the three long screws that hold the electron gun assembly together.
  9. Remove the V1 emission screw
  10. Remove the 2 filament couplers from the filament posts. You will need a .048 4 spline wrench.
  11. Remove the 3 filament ceramics.
  12.  Remove the filament assembly. Note the orientation of the emission tab and filament posts.
  13. Remove the 3 screws that hold the filament base on and remove the filament.
  14. Install the new filament in the same orientation as the old filament into the emission cap.
  15. Install the 3 screws and the filament base and tighten slightly.
  16. Position the filament so that it is centered in the hole and tighten the 3 screws. This is best done using a microscope.
  17. Install the filament assembly on top of the 3 filament ceramics and use the 3 long screws to hold the assembly together. The three long screws need to be tightened firmly so that they all have the same distance with respect to the base.
  18. Reconnect the V1 wire
  19. Reconnect the filament couplers.
  20. Ohm out the connections to the filament and V1.
  21. Degauss the gun assembly.
  22. Install the inner cylinder over the electron gun assembly.
  23. Reinstall the upper outer cylinder.
  24. Carefully install the conical ceramic. The resistor part should be 180 degrees out from the center flat ceramic. Ohm out VM to ground and make sure it has the correct resistance. See the Conical Ceramic PDF file for more information.
  25. Install the inner magnetic shield
  26. Degauss the analyzer.
  27. Install the outer magnetic shield.
  28. Degauss the analyzer. Installation complete.

 SCA (Spherical Capacitive Analyzer)

The PHI model 10-360 SCA analyzer is uses a different approach than the CMA which results in a higher transmission (better collection of signal).   Since there are no grids in the SCA, the only maintenance normally required is the replacement of the electron multiplier.

There are three types of detectors used in the SCA. They are, single channel multiplier, PSD (position sensitive detector) and MCD (multi channel detector).

10-360 Detector and multiplier cross reference:

System Model Description Specifications Detector Type Multiplier type

5100

 Large Area 2 X 10mm Single channel Channeltron

5300

 Large Area 2 X 4mm Single channel Channeltron

5400

 Small Spot 200uM PSD Channel plates

5500

 XPS/AES 75uM MCD Chevron

5600

 XPS/Scanning AES 30uM MCD Chevron

x-ray photoelectron spectrometer

 

Ion Guns.

Hot Filament type

The most common type of ion gun is the hot filament type.  A filament is heated up white hot and electrons are accelerated into the ionizer grid assembly. Argon gas is either injected or back-filled into the ionizer grid where electron impact converts the Argon atoms into Argon ions which are then accelerated towards the target.

Hot Filament Ion Guns have many things in common including:

  • Filaments
  • Ionizer grid assembly
  • Extractor assembly
  • Condenser and Focus lenses
  • Insulating ceramics
  • Deflection plates
  • Ceramic feedthroughs
  • High voltage insulating ceramics
  • Copper and tantalum wire
  • Coupling connectors
  • Set screws

PHI Ion Guns that RBD services:

Model Number Description Specifications Filament type
04-161 2kV Backfill 2mm beam size Dual tungsten
04-162 2kV Backfill 2mm beam size Dual tungsten
04-191 5kV Backfill 1mm beam size Dual tungsten
04-192 5kV Backfill 1mm beam size Dual tungsten
04-300 4kV Backfill 1mm beam size Tungsten
04-303 5kV Backfill 200uM beam size Tungsten
06-660 Duoplasmatron 5uM beam size Anode/Cathode
06-670 Cesium 5 uM beam size Frit assembly

04-161 sputter ion gun schematic