Bi on Si(111)
Day before: HF dip and load sample. I generally run my STOs in the morning because they're short, but you can set up the Bi one to run overnight if you prefer.
Growth day:
Morning: Set Bi tip to desired temp. Bi base and tip will heat up. Ramp up time ~ 1 hour
Go to lab
Move trolley from LC to BC. Close gate valve. Load first Si wafer onto HTS. Move trolley as far as possible from HTS. Bake for 1 hour at 450 C.
Set HVP to 25
Record background pressures
Make sure CAR is in transfer position
While baking, run Bi STO (see recipe section). The Bi tip temperature / BEP conversion is very stable over time.
After STO, double check Bi BEP manually
Turn off beam flux IG
Ramp up RHEED to 1.5 A and 10 kV
After HTS bake, set HTS to 10, wait for temperature to drop below 250 C
Move first sample from HTS to GC
Move first sample from HTS to trolley
Set substrate heater to manual
Open GV between GC and BC, then shutter. Make sure to lock shutter in open position
Transfer off RHEED block
Transfer in first sample
Close shutter, then GV
Put substrate heater back in auto, set to 450 C for away bake (10 - 15 minutes)
Transfer second sample to HTS, start second sample HTS bake
After away bake, start "deox" bake (not a true deox, actually desorbing hydrogen passivation + any crap)
Rotate CAR to growth position
Open RHEED to check wafer has made it
Start substrate rotation
Set substrate temperature to 750 C (thermocouple)
Stop substrate rotation (rotating above 800 C may damage the CAR bearings)
Set substrate temperature to 990 C (thermocouple)
Deox bake for 15 minutes at 990 C thermocouple. This should be 740-760 C pyro. Since it's the max temperature, and I use it every time, I don't check with the pyro on every growth. The pyro doesn't monitor the low temperatures I need for growth very well, and black body doesn't work well for Si, so I use the thermocouple (TC) for everything.
After deox, cool down and face cryoshroud
Set substrate temp to 5 degrees below desired growth temp
When TC < 750 C, start substrate rotation
When TC < 650 C, stop rotation. Manually rotate CAR past transfer position to the hard stop. The CAR is now facing the internal GC cryoshroud. The purpose of this is to prevent crap desorbed from chamber walls from 990 C to land on cooling sample, and to speed up cooling
Wait for TC to be about 10 degrees ABOVE desired growth temp. This takes ~1.5 hours.
MAKE SURE to come in before TC reaches set temperature - otherwise significant power oscillation will occur and overly increase the temperature
Remember to cool down HTS once second sample has finished baking
Set substrate heater to manual, power output 0
After first sample reaches set growth temperature, return CAR to growth position
Start substrate rotation, 5-10 RPM
Load Bi growth recipe with appropriate thickness, and growth rate for the BEP., run recipe
Monitor with RHEED and record the nominal thickness of the double lined to 1x1 RHEED transition. This is the point where the (012) to (001) transition should occur in XRD (corresponding to the A17 to A7 structural transition). Recording this each time can help us determine the transition dependence on substrate temp, growth rate, etc.
After growth, promptly transfer first sample to trolley
Replace with second sample and repeat as applicable
After finishing all growths
Transfer RHEED block back in
Move trolley with grown wafers to LC
Ramp down RHEED
Idle Bi cell
Turn on BF gauge
Set HTS to normal temp
Any other standard procedures I forgot to list
Unload sample and load for next grower