Growth Checklist
System Bravo Growth Checklist!!
First pass atempt by AMCDay Before:
Make sure that growth chamber and beam flux gauges are on and make sure that the CAR is in transfer position.
Put RHEED block on the substrate manipulator (CAR).
Make sure first wafer to be grown is on the buffer heater station (HTS).
Make sure the trolley is not in front of HTS.
Start source turn on for group-III's.
Morning Of:
Currently we are running source turn-on (STO) recipes that heat the sources then wait for the user to check everything.
Make sure the beam flux gauge (BFG) is on and facing the sources.
Check to make sure the base temperature is stabilized for tip only sources.
Turn on HTS to appropriate level for substrate.
If using Sb, make sure that it is in constant power mode.
After STO finishes cool down HTS
Map group five fluxes Sb first, As second if using both.
Turn off BFG.
Ramp up RHEED gun filament. First slowly to 1A. Wait for a couple of minutes, then slowly to 1.35A.
Ramp up RHEED gun voltage slowly to 8kV.
Each Growth:
Load Wafer and bake facing away from sources for 20min under appropriate group V flux.
Load next wafer to be grown onto HTS and bake, make sure trolley is not in front of HTS.
Flip wafer into growth position and begin deoxing:
Always heat wafer in growth position (labeled RHEED on the CAR controller) on the so Pyro reading is as accurate as possible
To check RHEED to see if wafer has deoxed switch to RHEED position (11 degrees up).
For GaAs Deox occurs near 580C and wafer can be baked at 600C for 10 minutes before growth
For GaSb Deox occurs near 530C and wafer should be baked at deox temp for 30min before growth as wafer starts to melt very near 530C.
Run Growth Recipe...make growth entry into Database!!! [[1]]
After wafer has cooled below 250C in growth chamber and 200C in HTS unload and load next wafer
unparsed and unmodified from Stanford... Please update!
MBE GROWTH CHECKLIST -- "because if you are not paranoid when you start, you become paranoid soon." -- Sylvia
Heat sources.
System 4: Set turbo - high speed, open CBr4 blue valve, Idle mode, and Remote.
If paranoid, make sure all shutters are closed, no wafer in chamber.
Check & adjust fluxes. Background should be below about 6e-10.
Simulate growth recipe. *Watch for stars* in output.
If paranoid, Check that As cracker is 800-1000C.
If paranoid, Check that nuts on shutter posts are tightened.
Load sample; make sure all 3 pins are tightly locked on car.
Make sure all viewports are closed.
Check As valve setting.
Turn off ion gauges. (Or at least turn emission current down).
Turn car to face sources; make sure it's rotating freely & visible thru port.
Turn rotation on; make sure set screw is removed.
Turn on substrate cooling (water or air), if available.
Turn up heated viewport one notch (20W).
Close gate valve to TT. If growing w/gas, check TT & ion pump pressures.
Make sure Eurotherms are in High if you use them.
Set shutters, As valve, CBr valve (and car?) to Remote (Computer Control).
Verify shutter "Computer Interface" lights are on.
Heat substrate to 350C, make sure As shutter AND valve open.
If paranoid, watch substrate temp closely: avoid overshoots.
Check TT pressure.
Heat substrate to 620-795C depending on wafer holder (new=hotter), wafer doping (SI=h
otter), and system (Sys4=hotter).
Turn on RHEED gun (2.85A, 8000V), open shutters after gun & before screen.
Check temperature at which RHEED pattern becomes streaky (oxide blow-off).
Leave 5 min at (670-780C) and make sure RHEED pattern is streaky.
Close shutters in front of RHEED screen & after RHEED gun, turn down gun.
Open Ga shutter for buffer growth.
Grow.
After growth, when temperature reaches 350C, close As valve, then As shutter.
If paranoid, make sure this happens correctly, don't trust computer.
Turn off substrate cooling *air*. (Don't shut off water: it will freeze!).
Stop rotation.
Turn on ion gauges. (Turn up emission current if you turned it down.)
Turn down heated viewport.
Cool sources. (Ga must be cooled slowly to prevent spattering, which causes oval defe
cts.)
Open ion pump.
When temperature falls below 100C, turn car toward load arm (away from sources).
When pressure falls below 1E-9, unload. (Tighten setscrew.)
System 4: set turbo to low speed ("LS" appears on display).