Category Archives: General Optics and Vacuum

General information on repair, maintenance, and operation of both PHI (Physical Electronics) and other manufacturers’ systems and components

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)

10-360 SCA resistance and capacitance tests

Turn off the card rack power before proceeding.

SCA HV connector-

Remove the large SCA filter box (that has the big black cable going into it) and check for the following resistances –

Pin 1 to 3 = 7.4 Meg ohms

Pin 1 to 2 = 4.5 Meg ohms

Pin 2 to 3 = 2.9 Meg ohms

All SCA HV pins should be open to ground

Remove the POS and NEG filter boxes.

POS to NEG on the SCA should be about 15 meg ohms.

Capacitance tests –

POS to chamber should be about 850 pF (.850 nF)

NEG to chamber should be about 200 pF (.200 nF)

MCD connector

All pins should be about 300 pF (.300 nF) from the pins to the chamber, except for the 4 center pins which should be about 100 pF (.100 nF).

All MCD pins should be open to the chamber.

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

Titanium sublimation pump operation

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The TSP (titanium sublimation pump) is used in conjunction with an ion pump to improve pumping efficiency.  It works by evaporating a titanium film onto the cryopanel or TSP shield. The titanium film is very reactive and so the gas molecules in the chamber that collide with the cryopanel wall will react with the titanium and stick. The titanium film also helps to replenish the ion pump elements.

On Physical Electronics surface analysis instruments such as X-ray photoelectron and Auger spectrometers, there are 4 filaments on the titanium sublimation pump flange. Since the lifetime of each filament is limited, having 4 filaments extends the time before needing to vent and replace the filaments.

When using a Boostivac or TSP control, I always recommend that you use the Cycle mode. The reason is that if you happen to get distracted while operating the TSP in the Continuous mode you may forget to turn the control off and could put much more titanium into the system than you planned on, and also burn up the filament.

To operate the TSP:

  1. Set to Mode switch to Cycle
  2. Press the Reset button (located under the Cycle Length Minutes knob).
  3. Turn up the filament current to just above 50 amps.  Note that the filament current will drop as the filament warms up. You want it to be at 50 amps after it warms up.
  4. Observe the chamber vacuum on the ion gauge control. The pressure in the chamber will come up as the filament heats up initially. Then, the pressure will drop as the TSP filament sublimates.
  5. After about 2 minutes the pressure will stop falling and start to rise again. At that point, turn the TSP control to OFF.  In the cycle mode, the filament will automatically shut off after about 2 minutes. But if left in the cycle mode it will turn on again once every 30 to 45 minutes (depending on what the cycle length time is set to).  It is better to turn the TSPs off when not in use in order to extend the filament lifetime.

Titanium sublimation pump

 

 

 

 

 

Common Questions

How often should I operate the TSP?

In general, unless you are pumping a high gas load you only need to use the titanium sublimation pump occasionally.  Many people will use them just once a week, on Friday afternoon so that the system can recover over the weekend for example.  If you are using them to help pump the chamber back down after being up to air, then they are used once every hour or so for the first few hours of the pump down process.  They should also be used after a bake out.

What vacuum do I need to be at before I use the TSPs?

You can use them starting in the mid 10-4 Torr range. In fact, they are very helpful at this vacuum level in helping start the ion pumps (which need to be in the low 10-5 or better vacuum to start). Typically the TSPs are operated after loading gassy samples to help the vacuum recover more quickly from the 10-8 Torr into the 10-9 Torr range.

How long do the TSP filaments last?

That depends on how often you use them, but on most vacuum chambers they will last for a year or more before all 4 filaments are burnt up. They should be replaced as part of any preventive maintenance program. Note that the filaments may not actually burn out before the titanium becomes depleted.  As the filaments are used up the maximum current that they will come up to is reduced. When they can no longer be driven up past 45 amps they are no longer effective and should be replaced.

Should I use the TSP filaments one at a time or rotate them?

My preference is to use them one at a time until that filament is shot and then move onto the next one. The exception is that I outgas all 4 filaments into the turbo pump for 2 to 3 cycles anytime that new filaments have been installed. Out-gassing the new TSP filaments into the turbo pump will significantly reduce the outgas load on the ion pumps.  Each time you vent the chamber you need to outgas the filaments into the turbo pump as part of the pump down procedure.

How to replace the filaments:

Replacing the filaments is very simple; there are only 2 things that you need to know:

  1. Make sure that the filaments face out from the center post on the TSP assembly. The reason is that the filaments should warp out of position away from the filament shaft. If you face them towards the shaft then the filaments will short out and melt when they warp. See the pictures below.
  2. Use pliers to hold the copper coupler when tightening the filament to the shaft to prevent the shaft from bending. You need to tighten the couple quite a bit to make sure that the filament does not loosen up as the filament heats up. Note that the copper couplers get soft from use and so you may need to replace them when you change the filaments.  If the coupler strips out it needs to be replaced.

TSP Filament orientation

 

 

 

 

 

 

 

 

 

Warped TSP filament

Warped TSP filament

 

 

 

 

 

 

 

RBD Instruments provides replacement titanium sublimation pump filaments, TSP flange assemblies and offers repair services for the Boostivac and TSP controllers.

Ion pump element rebuild procedure

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Ion Pump Element Tech Tip – Flip the plates

After a number of years it becomes necessary to replace the ion pump elements used on surface analysis instrumentation such as X-ray Photoelectron spectrometers (XPS), Auger (AES), and Secondary Ion Mass spectrometers (SIMS). But what if you can’t afford the cost of new ion pump elements? Depending on how worn out the plates are, you may simply be able to “flip” the plates.

This procedure is written for the DI (Differential Ion) pump elements used on most PHI surface analysis and Perkin Elmer vacuum systems. However, it can also be applied to other ion pump elements such as Varian, which are used on many general-purpose vacuum systems.

Ion pump elements have three basic components: magnets, an anode, and two cathodes. For the DI pumps, one cathode plate is made out of tantalum and the other cathode plate is made out of titanium. Using cathodes made from these two materials provides good pumping stability for both inert and active gases. The size of the pump is determined by the number of elements used. For example, a Perkin-Elmer 120 l/s ion pump has 4 elements and a 220 l/s ion pump has 8 elements.

ion pump element

Ion pump element

The magnets cause electrons, which are created as part of the ionization process, to spiral in the anode. This in turn increases the probability of a collision with a gas molecule. When an electron collides with a gas molecule, the gas becomes ionized and the molecule is accelerated into a cathode. Over time, the cathodes become sputtered away and the ceramics that isolate the anode become coated and conductive. Also, flakes can form and accumulate, which can cause arcing from the anode to ground. As a result, the pump elements’ performance is greatly reduced and the elements need to be removed and inspected.

Usually, the pump elements need to be replaced. However, if the plates are not sputtered all the way through, it is possible to simply “flip” the plates, clean the anode, and replace the anode-isolation ceramics. Functionally, the ion pumps will be good as new. They will not last as long as new ion pump elements because the plates will not be as thick as new elements. You can, though, often get an extra 2-to-5 years of usage from the elements depending on your base vacuum, gas load, etc.

In the image below, you can see the anode, cathodes, and the heavily coated anode-isolation ceramics. Before you disassemble the elements, make a note of the position of the anode tab. One of the elements usually has the tab on the opposite side from the others. You will reassemble the elements so the tab is in the same location.

coated ion pump element

Coated ion pump element

Disassembling and Reassembling the Ion Pump Elements

Wear gloves and use clean tools when disassembling and reassembling the ion pump elements.

  1. Use a slotted screwdriver and a 5/16″ open end wrench to remove the screws and nuts that hold the elements together. TIP: Use isopropanol as a lubricant to prevent the nuts from seizing.
  2. Use a small flat-tip screwdriver and a pair of pliers to bend the ceramic shield tabs up.
  3. Lift each ceramic shield out of its support bracket to remove the anode-isolation ceramics.

The graphic below shows the components once the pump elements have been disassembled: the anode plate, the cathode plates, and the support brackets

.ion pump anode and cathodes

The image below shows the cathode after it has been sputtered. The sputtered areas look like pin holes. In this example, the sputtering is only about ½ of the way through the plate, which means that there is a lot of material left.

Sputtered ion pump cathode plate

Sputtered ion pump cathode plate

As shown in the picture below, we can see that the cathode is not sputtered all the way through when we flip it over; there are no holes on this side of the cathode. Because the center of the sputtered area will most likely not line up perfectly when the plate is flipped, the lifetime of the pump will be extended.

un-sputtered ion pump cathode

Un-sputtered ion pump cathode

The picture below is an example of a plate that is sputtered all the way through. In this case, the ion pump elements need to be replaced and not rebuilt.

sputtered ion pump cathode

Sputtered ion pump cathode

The picture below shows a clean ceramic and a coated ceramic. RBD Instruments provides the new ceramics. Please visit the Parts – Vacuum related section of our website at www.rbdinstruments.com.

ion pump ceramics

Ion pump ceramics

Once you have disassembled the elements, the rebuild procedure is very simple:

  1. While wearing gloves, use a clean wire brush to remove any flakes from the plates, anode, support brackets, and ceramic shields. Note that you do not need to remove all of the deposits and discoloration on the parts. Just make sure that whatever remains will not come off easily. The important thing is that the active portion of the plates is now fresh, the ceramics are new, and there are no loose flakes that can cause shorting.
  2. Install new ceramics. TIP Use a channel lock pliers to crimp the tabs on the ceramic shields that hold the ceramics in place.
  3. Flip the plates so that the fresh side is facing the anode. Because the tantalum plate is thinner the titanium plate, most elements will have a thin steel plate on the tantalum side of the cathode. The tantalum plate will be noticeably heavier than the steel plate.
    Make sure that you put the clean tantalum side towards the anode. The picture below shows the dirty element after the plates have been flipped and reassembled. It may not look pretty, but it will work as well as a new element.
rebuilt ion pump element

Rebuilt ion pump element with flipped plates

Assemble the plates and support brackets, as shown in the picture above. Make sure that the support brackets are holding the anode snuggly as you tighten the screws and nuts.

 Installing the Elements Back into the Pump Well

  1. Before installing your rebuilt or new ion pump elements, use a wire brush and a vacuum cleaner to clean the pump well and remove all flakes that are inside the pump well. You can also wipe the inside of the pump well with a Kim wipe or lint-free cloth and some isopropanol. You want the pump well to be as clean as possible as any remaining flakes can cause shorting in the elements, which would require that you disassemble the ion pump again.
  2. If possible, bake your vacuum chamber into the turbo pump for 4 hours.
  3. Let the ion pump cool down before you try to start the ion pumps. Removing as much water vapor as possible will make the ion pumps much easier to start.
  4. Start the ion pump.
  5. Pump the chamber until you are in low 10-7 or low 10-8 Torr range.
  6. With the ion pumps on, bake the chamber again for an additional 8-to-24 hours.

If you need more information on this procedure or would like to order the ceramics or new ion pump elements, please contact us.

Here are some pictures that show an ion pump being lowered:

Dropping the pump well

Dropping the pump well

Pump well down

Pump well down