Ion Gun Align

• Use Si 10 um grid 30 degree tilt, sputter off O and C.
• SEM multiplier off and beam blanked.
• Hemisphere CAE 10 eV at 56 eV, entrance slit  3, 2 mm circle
• detect SE from ions
• At 3 kV ions, best focus ~ OBJ 62
• Currents to sample (no bias)
• cond 100, 55 nA
• 95, 85 nA
• 90, 166 nA
• 85, 310 nA
• 80, 700 nA
• around 60, 6.6 uA
• spot center ~ x=1.3, y=0 (at cond 90 obj 70, only weakly dependent)

make Foundry1 profile, 25 mA, grid 150, pressure 20 mPa

cond 85 obj 62 voltage 3000

Auger test postbake

Auger

• Test auger after bake. Reduce multiplier voltage to 8.2 from 9.0, negligible loss in counts.
• Get nice spectrum from Au on C, even 70 eV Au peak at 8 kV.

Align after bake

This is the procedure for a full "service" alignment, this is not for daily fine tuning alignment

Simplified Column Alignment instructions

1. Put large featureless sample, at least 3-4 mm, such as Si wafer in stage, no tilt
1. Get image at 8 kV, focus on sample
2. open "Aperture Calibration" and "Calibrate Stigmation" windows (these only work in service mode)
1. Select probe current max
2. zero gun align and aperture align in service window AND user aperture window
3. zero stig and beam offset
4. All electronic offsets should be neutral
3. Get emission image, uncheck Condenser Normal box
1. all apertures should be evenly illuminated, circles will overlap
1. If circles are clipped, distorted, partial, mechanical source align is required
2. if illumination is good, mechanical source alignment is OK,go to next step
3. loosen 4 6 mm screws at top of column. do push-pull adjustments in X and Y to try to get uniform illumination. 
4. to the extent possible, center illuminated aperture pattern, however uniform illumination is more important than centering.
5. recheck condenser normal. Now large diffuse aperture images will change to sharp smaller circles. These should also be uniform. Reduce SEM contrast since these will be saturated.
6. slowly tighten all four screws to lock source. This will cause shifts, correct as needed to get good illumination with source locked. 

Best align with current filament state, 200 pA mode (60 um aperture)
gun 44.5, 27.5 aperture -47.0 -22.9
user aperture -4.0, -6.0
stig 5.7 19.5 balance X 81.3, 95.9 Y 69.6, 94.7

Best max current
gun 44.5 27.5 aperture -47.0 -22.09
stig 24.7, 39.0 bal X 84.1, 93.0 Y 74.3, 94.7

Condenser lens needs mechanical alignment. Here is emission image for 1 nA, 600 pA, 400 pA all 90 um aperture

clear shift with condenser excitation















Align gun, aperture, stig, stig balance for 120, 90, 60, 30 um apertures

SEM Source Mechanical Align

Prior status

• just after bake, EHT off current up 246 vs 232
• Gun align near user software limit, stig balance off, time for full align

Align

8 kV aperture image condenser at "max"

aperture positions:

1. 60 um center
2. 20 um right
3. 30 um lower left
4. 75 um lower right
5. 90 um left
6. 120 um top right
7. blank top left

Procedure

First check mechanical alignment, use Si 10 um grid for test

Alignment, all offsets zero user and service. Cond normal

condenser off

Clear problems with mechanical alignment

Bring aperture to exact center, bad illumination

very poor aperture illumination on exact mechanical center

condenser on, illumination distorted here too

Procedure says illumination trumps centering

illumination better but is 120 better than 60??

best mechanical source alignment

after this use gun offset/align for center aperture

Post Bake tests

Problems

• FIG5 ion gun filament burned out
• Sample clips on STM stage too loose for good electrical contact, impossible for STM
• Manifold changes needed, existing manifold not optimized, leaking
• evaporator filaments cross wired, not working

Repairs

• FIG5 filament removed, replace with old 04-303 ionizer assembly, almost identical to FIG5 except 3 post rather than 5 post. Send failed ionized to RBD for rebuild
• Stage removed, clips removed, bent to improve sample plate grab, re-installed
• left clip electrically connected to metal "U", right clip isolated
• tricky to get right clip not to short to U since mounting screw passes through kapton washer into U
• changes to manifold, old stuff mostly removed

Bake

• Set for 72 hours, stopped 6 hours early (clock fast)
• bake into turbos, ion pumps open but off
• nano goes to 3e-5 at full temp, constant during bake
• prep 8e-6, slowly drops to 6e-6
• heat off drops to low 8's, with ion pumps running mid 9's, after TSP high 10's
• next day nano 2.5e-10, prep 3.5e-10
• 
  

Ion Gun

• Brief test of filament before bake, 1 mA emission >> 50 mPa extractor, too much outgassing
• After bake, nano 6e-10, FIG5 pump running
• Turn on 1 mA, grid 150 V, beam 0.5 kV, initially no pressure change, extractor or system
• filament will not come on in standby, must go to etch first. go figure.
• Turn off power supply and software, verify filament continuity, turn back on
• this time it works. probably software. Saved "foundry degass" profile new values
• 150 V grid, 1 mA, 500 V, 100% cond obj
• initial pressure 30 mPa, chamber 1.1e-9, 10:45 am
• pressure exceeds 50 mPa 11:15, gun shuts down self-protect, restart at 0.5 mA, initial pressure 14 mPa
• gun off again after 6 min, reduce emission to 0.2 mA, 28 mPa, later to 0.1 mA at 200 V, emission still > 80 mPa
• pressure peaks around noon, starts slow decline, still 0.1 mA 200 V etch
• 3:45 pm now 1.8 mPa at 25 mA. Note pressure may be normalized by emission current in software, higher current seems to reduce reading
• start to condition HV, pressure about 1 mPa now, 4:45 pm
• OK up to 3 kV, later 5 kV
• extractor still 2 mPa in standby

SEM startup

• connect all cables except detectors, including interlocks and column valve
• switch electronics on to standby, verify column valve closed, switch to on, valve opens
• forgot to start water chiller, SEM water flow error
• start chiller, cycle to standby, restart server, still get flow error
• confirm water is running. Open console whack water flow sensor, right side front behind electronics board, restart, still get flow error
• cycle power 5 times, keep hitting, keep getting flow error
• Remove and dis-assemble and clean flow switch, Gentech International 1 liter/min, closed on flow. No problems with switch.
• Flow is actually low. Run output into bucket, some black powdery crud. Flush with ~ 50 liters water. 
• adjust chiller from 2.6 to 3.3 pressure limit (zeiss spec 3.0 bar)
• disable filter change alarm (we have no filter, its optional)
• Now flow switch works
• Now column valve fails. Limit switch does not light. It did on the first run. Loosen tiny set screw so magnetic indicator works
• Close nano chamber gate valve, let pressure rise to mid 8's so zeiss ion pump will start.
• Start gun ramp up
• quick rise to 156 uA, slower increase to 167 and rising
• EHT on 3 kV, gun pressure 7e-9 mbar
• EHT off, 1:45 after gun start, gun 5.3e-10 mbarr, 209.5 uA at 5.02 kV 2.33 A
• next day 5.4e-10, 246 uA
• prior to bake was 223 to 234 back to Jan 2013, around 230 last six months

Manifold

• Ar source, Nano Ar gun, bypass all connected with VCR manifold
• Pump manifold, air lock, gun connection, Ar source, 4.0e-5 after 45 min, let pump over night.
• Overnight 4.1e-7
• apparent small leak in ion gun branch, close valve drops below 4.0, open after few min up to 5
• close manifold valve, no additional drop
•