Edwards 306 procedure from cold.

C.S. Allen 08.10.2012

  • Turn on power at the wall.
  • Ensure that valve handle is set to closed (pointing directly down).
  • Turn on the rotary pump.
  • Turn the valve handle clockwise (CW) to backing, this will connect the roughing pump to the diffusion pump exhaust line.
  • Wait for the backing pressure (on the pirani gauge) to reach the marked value (6x10-2 Torr).
  • Turn on the diffusion pump and allow approximately 20 mins for the oil to warm up while being backed by the rotary pump.
  • Meanwhile, vent the chamber by pressing the air admit button and turning on the pressurized air line. If the pressure in the air line is too high the solenoid valve will fail to open. NB. Ensure the penning gauge is OFF before venting the chamber.
  • Once vented remove the implosion guard and then CAREFULLY remove the bell jar, turn off the air admit button and close the pressurized air line..
  • Place your material in the correct boat and attach your samples to the sample plate. Replace the sample plate ensuring the hole lines up with the crystal monitor. Check the shutter is properly aligned and has enough travel to completely cover and uncover the evaporation boat. NB. Always wear gloves when touching anything inside the evaporation chamber.
  • Run your finger around the seal and base plate to ensure there are no particles and then CAREFULLY replace the bell jar and implosion guard.
  • Once the diffusion pump has been on for 20 mins (while being backed by the rotary) turn the valve handle counter clockwise (CCW) past closed to roughing. This closes the valve between the rotary pump and the diffusion pump and opens a valve between the rotary pump and the deposition chamber.
  • Rough pump the chamber until the backing pressure reaches the marked value (8x10-2 Torr is o.k.), but do not leave the diffusion pump un-backed for more than 5 mins. If the backing pressure does not drop within 5 mins seek help.
  • Once the backing pressure reaches the marked value turn the valve handle CW past closed to backing and wait for the backing pressure to drop to the marked value once again.
  • At this point you can turn on the penning gauge on range 1, the pressure should read < 10-3 mbar.
  • SLOWLY turn the valve handle CW to open the valve between the diffusion pump and the main chamber. Watch the backing pressure (pirani gauge) and when this begins to increase stop opening the valve until it recovers. Continue to slowly open the valve (valve handle CW) while monitoring the backing pressure.
  • Once the valve is completely open slowly fill the cold trap with liquid nitrogen until it overflows.DO NOT PERFORM AN EVAPORATION WITHOUT LIQUID NITROGEN IN THE SYSTEM.
  • Monitor the chamber pressure via the penning gauge changing range as necessary. DO NOT begin evaporation until the chamber pressure is < 1x10-5 mbar. After about 40 mins the pressure should have dropped to 1x10-6 mbar.
  • Set the crystal monitor to the appropriate layer for the material you are going to deposit and check the ρ and Z values and the tooling factor (scroll through the various options by pressing data, you can only change values when the shutter is set to closed).
  • You are now ready to evaporate. Ensure the correct material is in the evaporating position and that the shutter is covering your sample.
  • Press the green reset button and then press the LT (low tension) button.
  • Ramp the current at a rate of ∼5 A every 30 s to the required deposition current (check the log book for deposition currents of different materials).
  • Manually open the shutter and press open shutter on the crystal monitor to start recording deposition rate.
  • If necessary slowly increase or decrease the current to get the desired deposition rate (∼0.1-0.2 nm/s is a good rate, donít exceed 0.5 nm/s). If there is no deposition occurring at currents in excess of that used by other users (check the log book), slowly decrease the current to zero and seek help.
  • Once your desired thickness is reached manually close the shutter and press close shutter on the crystal monitor.
  • Slowly decrease the current to zero and then turn off the low tension (press LT) and press the small red trip switch to isolate the power supply.
  • If you want to deposit another material rotate the carousel until the desired material is in the deposition position and follow from point 19.
  • Once all deposition is complete turn off the penning gauge and the crystal monitor, fill in the log book and allow 30-40 mins for the system to cool down.
  • Once the system is cool turn the valve handle CCW to backing, and if no one else is going to use the evaporator turn off the diffusion pump (it is important to leave the roughing pump on and the valve in the backing position for 30 mins to allow the diffusion pump to cool down).
  • The chamber can now be vented (ensure the penning gauge is turned OFF) by pressing air admit and turning on the air line, your samples removed and the sample plate and bell jar replaced.
  • Once the diffusion pump has cooled (∼30 mins after turning it off) turn the valve handle CCW passed closed and rough out the evaporation chamber until the pirani gauge reaches the marked value.
  • Turn the valve handle CW to closed, turn off the rotary pump and turn off the power at the wall.
Evaporation material parameters
LayerMaterialρZApprox Evaporation current