The AVC (Auto Valve Controller) was developed by PHI (Physical Electronics) in the early 1980s and first appeared on the 5000 series XPS systems. It allowed for automaton of the opening and closing of vacuum valves on the chamber for functions such as loading samples or differentially pumping the ion gun.
The AVC comprises an electronic controller, which drives the pneumatic valves on the vacuum chamber, and a remote box, which provides a way to send requests to the controller and displays the status of the valves on the chamber.
The AVC remote box has 4 buttons:
DIFF PUMP ION GUN
There are two square buttons on the front of the AVC controller:
BACK FILL CHAMBER
There is a toggle switch on the front of the AVC controller – Auto and Manual. When in the Auto mode, the AVC remote box is used to open and close valves. When in the Manual mode, the little round push button switches on the front of the AVC controller (1 through 8) are active. When you press on any of those buttons the corresponding valve will open. Pressing the button again will close the valve.
The valves on the vacuum chamber are pneumatic right-angle valves and gate valves. The V1 gate valve needs air to open and air to close, most of the other valves need air to open and are spring-loaded closed.
The valve numbers and functions are:
V1 – Gate Valve. Isolates the main vacuum chamber from the load lock.
V2 – Vent valve. Provides 3 PSI of dry nitrogen to the load lock.
V3 – Load lock isolation valve. Isolates the turbo pump from the load lock.
V4 – Differential Pump valve. Isolates the ion gun differential port from the turbo pump.
V5 – Vent valve. Isolates 3 PSI of dry nitrogen from the turbo pump.
V6 – Pre pump valve. Used to pre-pump the load lock
V7 – Pre pump valve. Used to isolate the roughing pump from the turbo pump.
Note that not all systems have the pre pump option and so you may not have V6 and V7. The AVC remote has a schematic that indicates how your system is equipped.
Connections to the back of the AVC controller:
J1 TC1 – Connects to a Hastings DV6M gauge tube that is located on the load lock.
J2 TC2 – Connects to a Hastings DV6M gauge tube that is located on the turbo pump.
J3 Probe – Connects to load lock probe position sensor
J4 Ion – Connects to ion gun remote, normally not used
J5 DIG – Connects to setpoint 2 on the DIGIII ion gauge setpoint relay
J6 Status – not used
J7 208VAC input line voltage
J8 40 pin connector to AVC remote
J9 Up to air – connects to turbo pump controller, lets the AVC know that the turbo pump is ON
J10 Solenoid power – connects to solenoid manifold
J11 Cold Cathode gauge used only on LS systems
There are two modes of operation, AUTO (automatic) and MAN (manual). The mode switch on the front of the AVC controller sets the mode.
In the Automatic mode the microprocessor in the AVC makes sure that valves open in the correct sequence. For example, the AVC will not open the V1 gate valve to load a sample unless the load lock has been pumped out first.
When operating in the Manual mode the valves will open when the buttons on the front of the AVC controller are pressed. The valves will close when the buttons are pressed again. When operating in the Manual mode, you need to be very careful which valves you open as it is possible to dump the chamber (bring it up to air very quickly) and damage internal components such as filaments and electron multipliers.
Automatic Mode of Operation
Toggle the mode switch on the AVC controller to AUTO.
Load a sample mount:
- If your nitrogen is connected to a bottle, make sure that the valve to the nitrogen bottle is open.
- Press the BACKFILL INTRO on the AVC remote. V3 will close if not already closed and V2 will open.
- Rotate the cap on the load lock so that when the load lock is backfilled with nitrogen to 3 PSI the cap will be able to be easily removed. Sometimes the cap will pop off or flutter from the nitrogen pressure.
- Once the load lock is up to air, remove the intro cap then dock the sample mount to the intro arm. Most intro arm probes are magnetic, some of the older systems have a probe that slides between two Teflon seals.
- Pull the intro arm all the way back and the sensor switch will close. That will let the AVC know that the probe is in position.
- Place the cap back on the load lock but do not twist it tight or you will build up some pressure (3PSI) in the load lock. You can twist the cap tight after the load lock starts to pump out.
- Press the PUMP INTRO button on the AVC remote. V2 will close and V3 will open. The turbo pump will spin down and then come back up to speed. If your system is equipped with a Pre-Pump option, then V6 will open and V7 will close. After about 30 seconds V6 will close and then V3 and V7 will open.
As the vacuum improves in the load lock, the bars on the AVC remote box will increase from one to four. After four bars, the fifth bar will come up after 2 minutes. Once you have 5 bars the sample will be able to be loaded into the main chamber. But keep in mind that the longer you pump out, the less water vapor will be introduced as well. I typically recommend 5 bars plus 5 minutes as the minimum amount of time to pump down the load lock before introducing the sample.
- Press the INTRO SAMPLE button on the AVC remote box. V3 will close and V1 will open. There will be a pressure burst and then the main chamber should drop into the low 10-7 Torr to the low 10-8 Torr range, depending on how long you pumped the load lock and how gassy your sample is. The longer you pump the intro, the lower the pressure burst.
- Push the load lock arm in and dock the sample mount to the specimen stage and then retract the intro arm fully. Once the intro arm is all the way out, then V1 will close automatically.
Retrieve a sample mount:
- Make sure that the intro arm is all the way back and that the cap is on the load lock.
- If V3 is not already open, press PUMP INTRO on the AVC remote and V3 will open automatically.
- Wait until you have 5 bars on the AVC remote box, plus a minimum of 5 minutes. For best results you should always be pumping the load lock when not loading samples or differentially pumping the ion gun.
- Press the INTRO SAMPLE button on the AVC remote. V3 will close and V1 will open. There will be a pressure burst and then the main chamber should drop into the low 10-7 Torr to the low 10-8 Torr range, depending on how long you pumped the load lock and how gassy your sample is. The longer you pump the intro, the lower the pressure burst.
- Push the load lock arm in and dock to the specimen stage. Lower the specimen stage down and then retract the load lock arm fully. V1 will close automatically.
Differentially pump the ion gun
- Make sure that the turbo pump is on and up to full speed. Some systems have two turbo pumps, one for the intro/load lock and one for the ion gun. If your system has two turbo pumps, make sure that the ion gun turbo pump is on and up to full speed.
- Press the DIFF PUMP ION GUN button on the AVC remote. V4 will open and the ion gun will be differentially pumped. You can now set the emission current on the ion gun and open the argon leak valve.
Back fill the chamber
- Make sure that the mode switch on the front of the AVC controller is set to AUTO.
- Make sure that the card rack power and all electron, ion and x-ray related power supplies are OFF.
- Turn off the ion gauge (on most PHI systems that is a DIGIII).
- Turn off the Boostivac or DIGITEL 500 ion pump control.
- The turbo pump(s) should be ON. This is to prevent the possibility of back-streaming of oil into the chamber.
- Press the BACKFILL CHAMBER button. V1 and V2 will open (V3 and V4 will be closed) and the chamber will backfill with dry nitrogen.
- Once the chamber has been backfilled (load lock cap can be removed) then you can turn off the turbo pump (s).
Rough the chamber
- Make sure that the mode switch on the front of the AVC controller is set to AUTO. The turbo pump(s) should be OFF.
- Make sure that all flanges are sealed and that the intro load lock cap is mounted.
- Press the ROUGH CHAMBER button on the front of the AVC controller. It will light up red.
- Turn on the turbo pump(s).
- V2 will close and V1, V3, and V4 will open automatically. The system should pump out to 5 bars on the AVC remote box in about 20 minutes. Continue pumping for another 10 to 20 minutes and then turn on the DIGIII ion gauge controller. You will need to outgas the TSP filaments and wait until you get into the low 10-5 Torr before starting the ion pumps. Once the ion pumps start (vacuum is in the 10-6 Torr and improving), you can press ROUGH CHAMBER button on the AVC controller one more time and all of the valves will close.
- The system will need to be baked out.
Manual mode of operation
The mode switch on the AVC controller must be set to MAN.
In the AUTO mode the AVC controller uses logic to make sure that valves are opened and closed in the correct sequence. When in the MAN mode, YOU are the logic and you open and close the valves.
Use extreme care when operating the AVC in the manual mode as it is possible to damage the system.
For example, let’s say that you have the load lock up to air and the intro cap is also not mounted on the load lock. All the filaments and high voltages for the controllers are ON. You then manually open V1. What would the result be? The answer – catastrophic failure! You would lose all filaments, probably the electron multipliers, and most likely crack some viewports. So be very careful when operating in the manual mode!
In the manual mode of operation, when you press any of the 1 through 8 buttons on the front of the AVC controller, the corresponding valve will open, except for the vent valve V5. V5 opens and closes automatically when the turbo pump is turned on. If your system is equipped with two turbo pumps, then the V5 vent valve is controlled by the ion gun differential pump turbo.
Here are some examples of when you might want to operate the AVC controller in the manual mode
- The DIFF PUMP V4 valve does not open. In this case you can manually press V4 if you know the turbo pump is up to speed. If you have just one turbo pump on your system, then you also need to make sure that V3 is closed before you open V4. After you are done sputtering, you would then need to close V4 before you do something like pump out the load lock.
- Roughing the chamber out. You may want to manually open V1 and V3 to pump out the chamber.
- Venting the chamber. You may want to manually open V1 and V2.
Finally, here are links to some other blog posts that are related to the AVC –