A blog on the repair, operation and calibration of surface analysis systems and components including electron spectrometers, sputter ion guns and vacuum related hardware. Click on the Index tab below to see a list of all posts. Visit our website at http://www.rbdinstruments.com
Physical electronics (PHI) cylindrical mirror analyzers ( CMA) use fringe field termination ceramics to reduce the fringe fields from the end of the cylinders.
Abstract an early patent:
Field termination plates for cylindrical electron analyzers are provided wherein the plates are constructed of an insulative material coated on the interior surface with a high resistance, electrically conducting coating. Spaced concentric rings of relatively high conductivity material in electrical contact with said coating are provided; the rings providing equi-potential regions on the plates, thereby minimizing field fringing near the ends of the cylindrical tube electron analyzer.
The PHI CMA (cylindrical mirror analyzer) utilizes conical and flat termination ceramics to eliminate electrostatic edge effects between the inner and outer cylinders. These ceramics are essentially gold rings with resistors in between that divide the outer cylinder sweep voltage down in even steps. The result is a very high throughput and even energy distribution of the Auger electrons. If a CMA has a poor contact on a termination ceramic, the results are noisy data and poor energy linearity.
Single pass AES CMAs have just 2 terminating ceramics, a conical at the front of the CMA and a flat at the base. Double Pass AES/XPS CMAs have 3 terminating ceramics, a conical at the front, a center and a base.
The conical and flat ceramics are essentially resistors and so the total resistance between the inner and outer cylinders add up like this:
The table below lists the values on the combined resistances of the older PHI CMAs.
Values are in Meg ohms
If the VM or IC to OC (inner to outer cylinder) resistances are off significantly in your CMA then you probably have a contact issue between a conical or flat (base) ceramic between the outer cylinder or the inner cylinder. Sometimes the resistances of the conical ceramic can be off due coating caused by years of sputter depth profiling.
A poor electrical contact can result in high background counts or extremely high noise levels in the data due to arcing. If you suspect that your CMA has a contact issue with a terminating ceramic then you will need to tear down your CMA to where you can add improve the electrical contact by adding some thin copper or gold shim foil between the suspect ceramic and cylinder. If you need some guidance on how to do that, please contact RBD Instruments.
The pictures below show the conical and flat ceramics from a 25-120A CMA. You can see the gold rings and also the thin film resistors.
For the purpose of checking the performance of a surface analysis spectrometer such as a cylindrical mirror analyzer (CMA) or spherical capacitive analyzer (SCA), looking at an ion induced low energy electron peak can be extremely helpful. The peak typically occurs at about 20 to 50 eV and the size if the peak is directly related to both the alignment of the ion beam to the analyzer as well as the amount of ion current.
Checking XPS Performance
Set up an alignment for a range of zero to 100 eV kinetic. The eV range in binding energy depends on which anode energy you have selected in the software. See the table below. Most systems use an Al anode, so the energy would be 1480 to 1380 eV (which is about 0 to 100 eV kinetic).
Using a blank sample mount, position a sample to the focal point of the analyzer.
Look under the Hardware Properties Menu for XPS and note the X-ray Anode type.
Set up an alignment with the following parameters:
Upper Limit 1480 eV if Al is the anode, 1250 eV if Mg is the anode.
Lower limit 1380 eV if Al is the anode, 1150 eV if Mg is the anode
EV per step .5 (or the closest selection .5)
Time per step 20 ms
Start the alignment and turn on the ion gun (no raster). You should have a low energy peak at around 20 to 50 eV kinetic.
If necessary, reduce the ion gun beam current to prevent the detector from saturating. (You can increase the ion gun condenser lens setting or reduce the emission current in order to reduce the ion beam current).
If you do not get the peak, then you have a problem with the analyzer or analyzer electronics. If you do, then the analyzer and electronics are probably OK.
This is a very useful technique for isolating a low signal XPS problem between the analyzer and the X-ray source. You can also use the low energy peak to rough in the alignment of the ion gun to the XPS analyzer focal point.
Checking AES Noise Level
Analyzer noise (noisy data) can be caused by these things:
Poor contact between the inner and outer cylinder terminating ceramics
Analyzer control
Electron Multiplier supply
Electron gun control or Electron gun high voltage supply
This technique will help isolate analyzer noise by determining if it is related to the electron gun, which in tern would be caused by the electron gun control or electron gun high voltage supply.
Overview
This procedure uses both the electron gun and ion gun as a source to generate low energy electrons. By comparing the relative noise levels, you can determine if the problem is related to the electron beam only, or both beams. If it is related only to the electron beam, then the problem is in the electron gun control or electron gun high voltage supply.
If both the electron and ion beams are noisy, then the problem is either the analyzer control, multiplier supply or poor contact in the analyzer. The analyzer control and electron multiplier supplies can be tested for noise using the appropriate calibration procedure.
Procedure
This procedure was written specifically for a Physical Electronics 600 scanning auger system, but the principles can be applied to other systems as well.
Set up an alignment with these parameters:
Lower Limit 0, Upper Limit 100, EV per step 1, Time per step 20 ms
In AugerScan, go to the Multiplier Properties dialog box and uncheck the Auto EMS box. This will keep the computer from trying to automatically set up the electron multiplier voltage.
In AugerScan, go to the Hardware Properties dialog box and make sure the input is VF1.
With the electron beam on and set up for a normal elastic peak, start the acquisition and manually adjust the 32-100 CMA electron multiplier until you have a maximum count rate of approximately 100Kcps. You will see a low energy peak around 20 to 50 eV depending on your sample.
Use the yellow cycle stop button to end the alignment and then save the file.
Blank the electron beam and turn on the ion gun. Do not use any raster.
Start the acquisition and manually adjust the 32-100 CMA electron multiplier until you have a maximum count rate of approximately 100Kcps.
Use the yellow cycle stop button to end the alignment and then save the file.
Compare the two files to determine whether or not they have similar amounts of noise. In the examples shown below, then electron gun as a source exhibits more noise than the ion gun as a source. In this instance the problem was isolated to a noisy emission supply in the 20-610 High Voltage supply on a 600 system.
Ion Gun Alignment
On systems that do not have scanning electronic guns for TV imaging, you can use the low energy peak to center the ion beam with respect to the analyzer focal point. If you have scanning then you can simply look at the ion beam in real time on a SiO2 sample.
AES Ion Gun Alignment Procedure (for non-scanning AES):
Using a blank sample mount, position a sample to the focal point of the analyzer (Elastic peak).
Set up an alignment with the following parameters:
Lower limit 0 eV
Upper Limit 100 eV
Time per step 20 ms
In the Multiplier Properties dialog box, un-check the Auto EMS Box.
In the Hardware Properties dialog box, make sure the input is V/F1.
On the 32-100, set the CMA multiplier switch to Analog and make sure the potentiometer is fully CCW.
Start the alignment and turn on the ion gun (no raster).
Slowly turn up the 32-100 CMA multiplier supply (or the 20-075 multiplier supply if you have an older system) until you have about a 100K cps low energy electron peak at 20 to 50eV. This should occur at no more than 2000 volts on the multiplier (5.0 on the 32-100 potentiometer).
Finally, adjust the X and Y position of the ion gun for maximum signal. The ion gun is now aligned to the focal point of the analyzer.
XPS Ion Gun Alignment Procedure:
Using a blank sample mount, position a sample to the focal point of the analyzer.
Look under the Hardware Properties Menu for XPS and note the X-ray Anode type.
Set up an alignment with the following parameters:
Upper Limit 1480 eV if Al is the anode, 1250 eV if Mg is the anode.
Lower limit 1380 eV if Al is the anode, 1150 eV if Mg is the anode
EV per step .5 (or the closest selection to .5)
Time per step 20 ms
Pass Energy 100 (or the closest selection to 100)
Start the alignment and turn on the ion gun (no raster). You should have a low energy electron peak at around 20 to 50 eV kinetic.
If necessary, reduce the ion gun beam current to prevent the detector from saturating. (You can increase the condenser lens setting or reduce the emission current in order to reduce the ion beam current).
Finally, adjust the X and Y position of the ion gun for maximum signal. The ion gun is now aligned to the focal point of the analyzer. Once roughed in you can use a piece of TaO5 to check the alignment of the ion gun with respect to the system microscope because when you burn through the oxide layer you will see a blue ring on the TaO5 sample. RBD Instruments provides TaO5 samples for this purpose.
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.
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.
Always use gloves when working with optics. This is to keep oils from your fingers from contaminating the optics.
Maximize space between all high voltage wires and ground to prevent arcing.
Avoid sharp points on all connections to prevent arcing.
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.
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.
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.
590 Filament Replacement Procedure
Remove the magnetic shield (4 screws).
Carefully remove the conical ceramic ring (4 flat head screws) and remove the conical ceramic.
Remove the outer cylinder (1 screw), careful not to force it. If necessary, use a heat gun to loosen it up.
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.
Loosen the 4 spline set screws on the top of the inner cylinder by 1 turn CCW.
Remove all but one of the eight screws around the middle of the inner cylinder.
Remove the upper inner cylinder grid cap (4 screws).
Holding on to the nose of the electron gun, remove the final screw at the middle of the inner cylinder.
Carefully pull the electron gun up and out of the inner cylinder. Be careful not to stress any of the wire connectors.
Place the electron gun on a sheet of aluminum foil.
Loosen the bottom cap of the electron gun (4 screws and 4 set screws)
Carefully slide the bottom cap down the ceramics for about 2”, enough room to get at the filament.
Remove the filament assembly (4 cap screws, 2 splines connecting the filament wires).
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)
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.
Allow the analyzer to cool down.
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).
Very slowly, (over a period of 1 to 2 hours) bring the filament up to 2mA of emission current.
Next, slowly bring the beam voltage up to 2kV (about 30 minutes from 500 volts).
Set the condenser on the 11-045 to maximum and do an elastic peak alignment.
Slowly increase the multiplier voltage until a peak is just visible.
Leave the multiplier voltage at this setting for 6 hours or more.
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.
Set analyzer on stand or use manuals and support analyzer on handles, facing up.
Remove outer magnetic shield (4 screws)
Remove inner magnetic shield (4 screws)
Carefully remove conical ceramic
Lift upper outer cylinder up and set aside on clean aluminum foil.
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.
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.
Remove the three long screws that hold the electron gun assembly together.
Remove the V1 emission screw
Remove the 2 filament couplers from the filament posts. You will need a .048 4 spline wrench.
Remove the 3 filament ceramics.
Remove the filament assembly. Note the orientation of the emission tab and filament posts.
Remove the 3 screws that hold the filament base on and remove the filament.
Install the new filament in the same orientation as the old filament into the emission cap.
Install the 3 screws and the filament base and tighten slightly.
Position the filament so that it is centered in the hole and tighten the 3 screws. This is best done using a microscope.
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.
Reconnect the V1 wire
Reconnect the filament couplers.
Ohm out the connections to the filament and V1.
Degauss the gun assembly.
Install the inner cylinder over the electron gun assembly.
Reinstall the upper outer cylinder.
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.
Install the inner magnetic shield
Degauss the analyzer.
Install the outer magnetic shield.
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
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:
