Loading Wafers
New Load/Unload Checklist
Vent Load Chamber
. Check that the LC pressure is adequately low for opening to the BC, should typically be below 6e-9 torr
. Move the trolley into the LC while monitoring pressures, esp. in the BC and LC
. Close the LC-BC gate valve
. Turn off the LC ion gauge
. Confirm the roughing manifold green quarter turn valve and black viton seal valve are closed
. Turn up the N2 valve labeled Chamber to about 20 psig (on lab wall)
. Confirm the N2 is flowing at the overpressure vale under the table—now the N2 line is purging
. Turn off the turbo pump while monitoring the BC pressure. If the BC pressure increases, turn the turbo back on immediately and figure out what is wrong. The LC pressure rises to low torr in ~10 seconds
. Wait for the turbo status light to stop blinking and turn off
. Open the green quarter turn valve under the table to purge out the roughing manifold (RM) N2 line entry
. Confirm on the SRS that the gauge labeled PG1 reads ~20-35 torr (depends on ΔP for PG1 and PG2)
. Wait for PG1 and PG2 on the SRS to ~equilibrate, which the above ~20-35 torr pressure should ensure
. Check the torque spec of the LC-RM all-metal valve (35 or 38 ft-lbs) and open the all-metal valve
. Unplug the scroll pump VPI from the power strip, to close it and prevent backflow
. Turn off the scroll pump by pressing the Pump Off button and confirm it is spinning down
. Immediately loosen the knob that controls the door to the LC and turn up the N2 purge to 25-30 psig
. Immediately close the green quarter turn valve and open the black viton seal valve under the table
. Immediately barely crack open the green quarter turn to gently flow in N2
. Allow the LC to vent to ATM, slowly increasing how open the green valve is til it is fully open near ATM
. At ATM, the LC door should pop open. Assist it if it gets stuck. Check the viton door seal is safe and seated
Prep Sample Loading Area
. If needed, put down new large kimwipes in the sample prep area. Start in the top left corner and move CCW
. Take off the top layer or two of large kimwipes
. Retrieve the ultra-clean loading tool bin from the desiccator by the front door
. Retrieve wafers for the next person’s growth. Cleave wafers into quarters if necessary. Set aside in container
Remove Trolley
. Open the LC door fully and use the magnet to get the edge of trolley out of the LC
. Put on an ultra-clean glove and pickup trolley through outside (empty!) sample position, but never when hot
. Carefully remove the trolley and, without it touching anything, put it on kimwipes in sample prep hood
Loading Trolley into Chamber
. Check that the LC door viton seal is intact and has not come loose. If it has come loose, see Notes below
. Pickup trolley through outside (empty!) sample position using an ultra-clean glove
. Put trolley into LC partway, engage the magnet, and use the magnet to pull trolley in fully
. Ensure the magnet is holding it in place in the chamber and centered on the LC lamp, and close the LC door
. Immediately close the green quarter turn valve to shut off the N2 purge to the LC
. Immediately tighten the door to the load chamber
. Immediately turn on the scroll pump, make sure it’s on, and plug in the VPI to pump down the LC and RM
. Close the viton seal
. Wait for the LC and RM pirani gauges to read ~20-35 torr (PG1 and PG2)
. Check the torque spec of the LC-RM all-metal valve (35 or 38 ft-lbs) and close the all-metal valve
. Turn on the turbo pump (light will blink) and wait until it fully spins up (light will be solid)
. Turn down the N2 valve labeled chamber to nominally off
. Confirm PG2 on the SRS reads in the mTorr range
. When PG2 reads < 1e-3 torr, turn on the LC ion gauge. If ion gauge reads greater than 1e-5, turn off and wait a few more minutes.
. Run an LC bake recipe. Make sure the recipe has a wait of at least1 hour before heating up
. Update the Trolley sheet
Swapping Faceplates
How to put away faceplate sets when swapping. They should go into the wafer mailers in the same order as in the blocks when on the nosepiece:
Front spring plate, growth side down, in first
Back spring plate, spring plate side down, in second
Backing wafer, deposition side down, in last if swapped.
Notes
. The Trolley is ultra-clean
. The trolley must have an open slot on the correct end in order to be picked up
. The trolley cannot touch anything it’s not supposed to!
. It is very important that the trolley is not handled when it or a block is hot! One small piece of glove can ruin a campaign!
. If you take out the nose piece (then the ultra-clean tool bin) before taking out the trolley, be super careful not to touch it
. Be aware of the fume hood acrylic flaps when moving things in and out, esp. the trolley and tool bin
. Always keep an eye on the LC door viton seal and check it is intact and has not come loose. If it has come loose, put on a new pair of ultra-clean gloves and push the seal back into the groove on the retaining plate. Failure to do this will squish the seal and tear it.
. Do not over-tighten the LC door nut. Once you start to feel resistance, another quarter/half turn or so should be good.
. Do not attempt this without first being shown how! Failure to do this will anger the other students.
. Be careful not to touch the substrate with even the cleanest glove or any not ultra-clean tools.
. When putting in new samples, take care to ensure the retaining rings are tightly seated in the ridge on the substrate holder. Shake wafer holder to ensure wafer will not slip in machine
. Once vented, the LC must be baked before opening it to the BC
. Wait until the LC lamp thermocouple reads below 50 C to move trolley into the BC
. Levels of cleanliness are: Trolley > ultra-clean tools = Nose piece > nose piece stand > ultra-clean tool bin outside > LC door outside
. Switch gloves as often as needed. I usually put on an ultra-clean glove to get out the ultra-clean tool bin, then a new one to take out the trolley, then a new one to get out the nose piece and open the ultra-clean tool bin, then a new pair to handle the nose piece and ultra clean tools.
Classic Maddox Procedure
Preparing the fume hood and tools.
If there are already clean kimwipes in the fume hood, remove the top layer or two. If there are not, put down all new kimwipes.
Clean tweezers and scribe if not ultra-clean.
Preparing for venting
Start purging the ultrapure N2 line to the roughing manifold by turning the regulator pressure to ~15 psi.
Move the sample trolley from the buffer chamber (BC) into the load chamber (LC).
Check that the LC pressure is adequately low for opening to the BC (it should typically be below 6x10-9 Torr).
Open the gate valve between the LC and BC.
Move the trolley into the LC.
Close the gate valve between the LC and BC.
Venting the LC and removing the trolley
Turn off the LC ion gauge filament.
Turn off the LC turbo pump. The leak valve into the turbo pump will open, and after ~10 seconds, the pressure in the LC should be in the range of 10 Torr.
Slowly open the all metal valve between the LC and roughing manifold, allowing the pressure to equalize. (Note: if the roughing manifold is at atmospheric pressure, it is best to wait to perform this step after turning off the backing pump)
After the turbo is spun down (hold your hand on it to feel if it is spinning--it will take a few minutes), turn off the backing pump.
Begin leaking ultrapure N2 into the roughing manifold using the green quarter turn valve. Make sure the viton seal valve above the green quater turn valve is open.
Watch the roughing manifold Pirani gauge and the analog relative pressure gauge. When the pressure is near atmospheric pressure (~760 Torr on the Pirani gauge or 0 on the relative pressure gauge), unscrew the nut keeping the LC door closed. The door should open by itself when it reaches atmospheric pressure, but you can help it out, since the viton seal can get stuck sometimes.
Leave the ultrapure N2 purge on, and turn to ~25 psi to minimize the amount of air that makes it into the LC.
Put a clean glove on over your current glove, and remove the trolley from the LC, being careful not to bend the pins.
NOTE: IT IS VERY IMPORTANT THAT THE TROLLEY IS NOT HANDLED WHEN IT OR A BLOCK IS HOT...ONE SMALL PIECE OF GLOVE CAN RUIN A CAMPAIGN!!!!
Put the trolley on the clean kimwipes
Unloading and loading wafers
NOTE: DO NOT ATTEMPT THIS WITHOUT FIRST BEING SHOWN HOW!!!!!! Failure to do this will anger the gurus (and the MBE gods). Their wrath is severe.
Being careful not to touch the substrate with even the cleanest glove or unclean tools, load and unload the substrates. Take care to ensure the retaining rings are tightly seated in the ridge on the substrate holder. Shake wafer holder to ensure wafer will not slip in machine.
Putting the trolley back in the LC
Using a clean glove, pick up the trolley and put it back in the LC. Make sure it goes in smoothly and far enough to grab with the magnet.
Move the trolley so it is in the middle of the heater (line up the trolley edge with that of the heater).
Make sure that the Viton seal on the door is intact and has not come loose. If it has then put on a pair of clean gloves and push the seal back into the groove on the retaining plate. Failure to do this will squish the seal and tear it.
Lightly close the LC door, turn off the nitrogen purge using the green quarter turn valve, and then tighten the LC door nut. Do not over-tighten the nut. Once you start to feel resistance, another quarter turn or so should be good.
Turn on the scroll (turbo backing) pump, close the all metal valve between the LC and roughing manifold, and soft start the turbo.
When the turbo is fully spun up, turn on the LC ion gauge, and run the LC lamp bake recipe in AMBER.
Wait until LC lamp thermocouple reads below 50C to move trolley into the BC.