Category Archives: Ion Sources

Information on PHI (Physical Electronics) ion source repair, maintenance, and operation

Duoplasmatron ion source rebuild procedure

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This procedure will help you to rebuild your PHI 06-660 Duoplasmatron ion source. On older ion columns the system needs to be vented before beginning this procedure. On newer ion columns there is a needle valve which allows the source to be removed and rebuilt with out venting the system.  This example is the older style ion column.

For best results, read this procedure before watching the video – Duoplasmatron ion source rebuild procedure

  1. After venting the system, remove the gas manifold at the source.  Protect the knife-edge with aluminum foil.
  2. Disconnect the differential pumping line.  Protect the knife-edge with aluminum foil.
  3. Support the differential pumping port with some solid object. Use aluminum foil to protect the knife-edge from becoming damaged.  The reason that this needs to be supported is so that when the alignment collars are removed from the column the bellows plate will not be supporting the total weight of the ion gun.  If this happens, the bellows plate may develop a vacuum leak.
  4. Remove the alignment collars by first removing the screws which hold the collar to the ion gun column. Be very careful when pulling the halves of the collar away from the COND and OBJ high voltage feedthrus.
  5. Remove the eight  ½” hex nuts, which fasten the source to the column. Be careful to support the source when you remove the last nut.
  6. Carefully remove the source from the column.
  7. Prepare a work area and cover it with clean aluminum foil.   Place the source on the work area and remove the outer shield.  Remove the top heat sink.
  8. Remove the second heat sink (3 screws) and the 6 screws, which fasten the cathode ceramic to the source housing.
  9. Remove the cathode ceramic by lifting it straight up.  Tip: make a lip on the edge of the aluminum foil to capture the red sapphire beams which will fall out when the cathode ceramic is removed. These sapphire beads insulate the cathode from the intermediate electrode.  (You can clean the nickel off of these beads with a small amount of diluted nitric acid and re-use them if you have access to a chemistry lab).

From This point on use gloves and clean tools.

  1. Turn the source over and remove the 4 screws, which hold the anode to the anode support housing.  Use pliers to lift the anode out.
  2. Remove the 4 screws  (also the washers and ceramics) that hold the anode support to the base of the source. Use a needle nosed pliers to lift the screws and washers out.
  3. Remove the ceramic at the base of the source.  Use a long needle nosed pliers, being very careful not to drop the ceramic.
  4. Remove the 4 screws, which hold the intermediate electrode to the base of the source and lift out the intermediate electrode.
  5. Install the new intermediate electrode to the base of the source.   Make sure it is clean.  If uncertain about the cleanness of the parts, ultra-sonically clean them in methanol and then isopropanol followed by drying.
  6. Replace the ceramic at the base of the source.
  7. Set the anode support on top of the ceramic. The spring tab should line up with the electrical feedthru.
  8. Set the ceramics back into the anode support.  Using pliers, place the washers and screws inside of the ceramics. Tighten the screws to attach the anode support to the base of the source.
  9. Replace the anode aperture (in the center of the anode), but punching out the old one and tapping the new one in place.  The spiral-grooved side should face down (towards the anode support).
  10. Replace the anode; tighten the four screws, which hold it to the anode support.
  11. Turn the source over and set it on top of the tabletop (so that is sits flat).
  12. Remove the old cathode from the cathode ceramic by pulling it and turning it counter clock-wise.  There is a screw in the base that should loosen up. If not, use a long Allen wrench to un-screw it.
  13. Install the new cathode to the cathode ceramic, using a new screw to hold it in place.
  14. Place a new gasket 1.33” copper gasket on the knife-edge.   Slide the cathode past the copper gasket, placing the red sapphire beads into the slots as you lower the cathode.   If you are having problems doing this you can drop the beads in a small amount of methanol. The capillary action will hold the beads in place while to lower the cathode.
  15. Tighten the cathode screws in a circular manner until the cathode is sealed.
  16. Replace the heat sinks and cover.
  17. Reverse the removal steps to place the source back on the ion gun column.    Very Important: Remember to place the alignment collar ring on the source before you replace the source on the column.

 

END OF PROCEDURE

 Additional notes:

The system MUST be baked out after working on a DP Source. The anode and intermediate are sensitive to contamination and water vapor. If not thoroughly baked out, flakes or whiskers will develop in a short period of time and the source will short out.  The gas needs to be pure and there must not be any leaks in the gas line. If air mixes with the gas the source will short out after a few hours of operation. Here is a procedure on how to pump out the gas line to make sure that the gas used for the DP is pure or if you have replaced the gas bottle:

DP gas line pump out procedure

This procedure explains how to pump the air out of the gas line after replacing the gas bottle.  For this procedure, the main chamber is under vacuum.  If the system is up to air then you can just pump the gas line down with the rest of the chamber by first opening the piezo valve on the gas line.

  1. Make sure that the 20-530 and 20-520 are OFF and that the valve select on the 20-530 is set to OFF.
  2. Remove the side panel on the vacuum console to gain access to the gas bottle manifold.
  3. Close the bottle and use a large crescent wrench to unscrew the gas line from the bottle.  Turn the large nut CCW to remove. Remove the gas bottle from the gas manifold.
  4. Make sure that the new gas bottle is tightly closed (CW).
  5. Put the new gas bottle in and attach the line. (Inspect the o-ring on the end of the gas line first to make sure it looks good). Firmly tighten the gas line by using a large crescent wrench to turn the nut CW.
  6. Keep the new gas  bottle closed at this time!
  7. Make sure that the turbo pump is on and up to full speed.
  8. Pump out the intro and wait until you get 5 bars.
  9. Differentially pump on the ion gun. V4 should open.
  10. Run an extension cord from the wall to the 20-530 so that it can be powered when the ion gauge is OFF.
  11. Turn the card rack power off and exit Auger scan and Auger Map.
  12. Turn the DIGIII or DIGIV ion gauge OFF
  13. Turn the Boostivac ion pump control OFF
  14. Turn on the 20-530 and make sure the ARC current switch is OFF. Turn the gas ON, set it to 10.
  15. Make sure that V3 is open.  If not, open it manually.
  16. Open V1 manually.
  17. Wait until the 20-530 pressure pumps down to zero.  This will take up to an hour or more.  If it does not drop to zero you have a leak in the gas line.
  18. Once the 20-530 pressure indicates zero, manually close V1 and V3.
  19. Turn on the ion pump control – set it to start and then run.  It should start right back up.
  20. Turn on the DIGIII or DIGIV.  The vacuum should be in the low 10-8 range and rapidly dropping into the 10-9 range.  It will take a day or so to completely recover.
  21. Allow the turbo pump to pump on the line (V4 open) overnight.
  22. The next day,  turn the pressure OFF on the 20-530 and turn the 20-530 OFF.
  23. Plug the 20-530 back into the system.
  24. With the 20-530 OFF and the gas valve set to OFF, open the gas bottle by turning the valve CCW.  Open it slowly at first and be prepared to close it quickly if the system pressure rises.   Hopefully, the valve should hold and you will not see any pressure rise. Open the valve fully CCW.

Gas bottle installation and pump down of gas line is now complete.

RBD Instruments no longer provides parts or service for the PHI DP ion guns or controllers.

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Faraday cup procedure to align ion beam current

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Using Ta2O5 or SiO2 works well for aligning an ion beam to the focal point of an X-ray photoelectron or scanning Auger electron spectrometer. But, in order to optimize the ion beam focus at larger beam sizes, a Faraday cup is required.

The Faraday cup used on many Physical Electronics/PHI surface analysis systems comprises a specially configured sample mount with a molybdenum aperture that has a diameter of 250um.

faraday cup sample mount

 

 

 

 

Because the current measured into the Faraday cup is in the low nA range, a picoammeter (such as the RBD Instruments Inc. 9103 USB picoammeter) and bias box are required. When the bias box is set to the ion input, the target is grounded and the output of the bias box is routed from the ion lead (Faraday cup) on the specimen stage to the input of the picoammeter. When an ion beam is larger than the 250um Faraday cup aperture, only the portion of the beam that is 250um or smaller is measured. By adjusting the ion beam focus and position for maximum current into the Faraday cup, the ion beam can be aligned and the current density can be optimized for any ion beam condition. In general, larger beam sizes result in more total current and faster sputter rates.

faraday cup

 

 

 

 

 

 

 

 

Another benefit of using a Faraday cup is that you can also determine the electric current density using a multiplication factor. Ion current density is rated in mA/cm2.Dividing the area of the 250um Faraday cup hole into one square centimeter gives us a factor of 2037.18. So, to calculate the ion beam current density using a 250um Faraday cup, measure the ion current that enters the Faraday cup and multiply it by 2037.18 to get the current density in mA/cm2. For example, the PHI 04-303 5kV differential ion source has a maximum current density specification of 600 mA/cm2 at 5kV ion beam voltage and 25 MPa of argon gas pressure. That works out to just under 300nA of ion current passing into the Faraday cup. Typically, though, the 04-303 ion source is operated at 3-to-4kV with 15MPa of argon pressure. Therefore, the maximum ion current passing into a Faraday cup under those conditions is more in the range of 150 to 200nA.

Procedure to Maximize the Ion Current Passing into a Faraday Cup

 

  1. First you need to align the Faraday cup to the focal point of the analyzer. For Auger electron spectrometers, acquire an elastic peak just to the side of the Faraday cup hole and then move the Faraday cup hole to the center of the TV image. For X-ray photoelectron spectroscopy systems, move the Faraday cup hole to the center of the system microscope’s image at the highest possible magnification setting.
  2. Turn the ion beam ON (make sure the electron beam is off).
  3. Set the bias box to Ion and the bias to ON. This will ground the target and apply +90V to the ion lead on the specimen stage (which in turn makes the electrical contact to the Faraday cup). Note that there are different versions of the bias box used on PHI systems. Some systems do not have bias boxes. In those cases, short out the target and and connect the picoammeter to the ion lead on the specimen stage.
  4. While observing the picoammeter, adjust the focus (objective) and condenser on the ion gun control and the mechanical offsets (thumbscrews) on the ion gun for maximum current into the Faraday cup. This will take several iterations to optimize. Once the mechanical offsets on the ion gun have been adjusted to where no further increase in current is noted, lock them down securely and also make sure that the ion gun housing is tight. Do not adjust the mechanical offsets for subsequent focus adjustments at different condenser (COND) or beam voltage settings. Instead, you can optimize the position of the ion beam into the Faraday cup by using the offset adjustments on the ion gun control if necessary.
  5. Note the measured current and ion gun settings in a form such as the table shown below. By optimizing a few ranges of current and using those parameters to acquire depth profiles on a standard such as SiO2 or TaO5 (both available from RBD) you can create a matrix of reproducible sputter rates.

Ion sputter rate table

 

 

 

 

Here is a link to a technical report in the Journal of Surface Analysis, which provides additional information:

http://www.sasj.jp/JSA/CONTENTS/vol.14_2/Vol.14%20No.2/Vol.14%20No.2%20124-130.pdf

And here is a link to a video that shows an ion source being aligned using a Faraday cup – http://www.youtube.com/watch?v=uKg9GLkXT3s

How to align the 04-303 ion gun

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This post explains how to align the Physical Electronics 04-303 ion gun typically found on PHI Auger electron spectroscopy and X-ray photoelectron spectroscopy systems. The alignment principles explained here will apply to just about any surface analysis ion source.

First, here is a video that explains all of the alignment methods:

Next, here is a link to a tech tip that explains the theory and operation of the 04-303 ion gun: 04-303 Ion Source Theory and Alignment

Finally, here is the basic operation and alignment taken from the tech tip:

04-303 Ion Gun Operation

Basic Operation:

1. On the 11-065, set the Emission/Pressure meter switch to Emission. Make sure that the scale switch is in the X1 (times one) position.

2. Press the Diff Pump Ion Gun button on the AVC remote, or manually pump the ion gun.

3. Slowly turn up the Emission knob until you have 25mA of emission current (X1 position).

4. Switch the Emission/Pressure meter switch to Pressure.

5. Slowly open the argon leak valve on the 04-303 ion gun until you have 15 mPa of pressure on the meter. This corresponds to approximately 2 x 10-8 torr when differentially pumped, and 2 x 10-7 torr when not differentially pumped.

You are now ready to sputter. When you turn the ion beam voltage on, the ion gun will be sputtering.

Alignment: Visual Method

This works in both ABS and SED image modes. SED mode is sometimes easier to work with.

1. Insert a SiO2 sample and position it to the focal point of the analyzer. Use 30o to 60o of tilt.

2. Get a low magnification image of the SiO2. Use a low electron beam voltage, such as 1.5kV in order to get the largest possible image size (the lowest possible magnification).

3. Set up the ion gun as discussed above. Set the condenser to 5.00 (the smallest spot size) and the objective to 3.40.

4. Turn on the ion gun beam voltage. If the electron beam current and the ion beam current are approximately the same value, the ion beam spot should be visible on the TV monitor.

5. Mechanically adjust the position of the ion gun (turn the thumb screws) to center the ion beam spot on the TV monitor. Adjust the OBJ for the smallest spot size.

For more information or to order a replacement ionizer for your 04-303 ion gun, visit our website at www dot rbdinstruments dot com