Ion gun imaging

• Want to use external raster control for 20-066 ion gun control to allow SE imaging for focusing and alignment
• Omicron software does not allow external raster to be enabled
• Install PHI software (from floppy disk!!) version 3.0A 1997
• C:\program files\PHI\EXE
• edit IonGunCrtl.ini

[Ion Gun Control]

ComPort=COM6

RS485ResponseTime=1000

IgunAddress=3

NoHardware=0

ModelNumber=11-066

BlankingOptics=1

[END]

Com port set to COM6, address used by Omicron. Other params left at defaults

Software seems to work.

Pressure control

• Phi software does not generate setpoint voltage
• switch RVG50C Pfeiffer controller to INT setpoint
• knob 1.0 = 13 mPa
• 1.5 = 20 mPa
• 2.0 = 26.5 mPa
• Leak valve needs 2.0 turns for ~ 30 mPa (as of 12/2/13)

PHI software raster

raster is not centered on offset, ie changing raster size shifts sputter area

Y raster half of X gives approximate square image for 30 degree tilt sample

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
• 
  

Vacuum problems during sample intro

• Granville phillips micro ion gauge controller shows 2e-5 air lock pressure
• degass gauge, jiggle connector cable, no help
• Leave pump running ~ 1.5 hour during sample transfer, analysis, then open gate valve
• prep still 8.8e-6, would expect better
• prep chamber 1.8e-7 (low 10's before opening), consistent with intro gauge
• close gate, pressure drops low 9's prep, increase to 1.7e-5
• Connect VQM cable to prep mass spec, turn on, mostly 18 amu in UHV
• open to air lock, lots of 32, 28, leak...
• pump air lock with prep ion pump, turbo valved off
• now mini IG 4.6e-7, prep 3.8e-8
• close valve to air lock, 14 and 28 drop, 18, 2, 44 relative rise, 1.9e-9
• reopen gate
• prep back to 3.8e-8
• 28, 14, 40, 32 rise, water related peaks fall
• now open turbo pumping valve
• pressure to 2.4e-7 prep, 9.8e-6
• 28, 32, 14 rise, also 40, air leak
• close turbo valve, pressure drops, 5e7 in air lock, 4.6e-8 prep, 14, 28, 32, 40 drop
• even with turbo valve closed, air lock pressure rises rapidly from mid 7's to 5's

Air leak in pumping, probably in manifold

• biggest leak was swagelock connected to mini flange at manifold pumping valve, tighten to reduce manifold to 1.1e-6 from 2e-5. 
• gasket (already suspicious) at 2.75" tee caught between flanges, ie offcenter, replaced.
• marginal improvement, still possible leak in manifold somewhere

Ion Gun trouble

Doing Auger alignment tests on Cu110 single crystal. Lots of carbon, system has been baked, maybe vented, since sample was clean. 64 V LVV peak hard to see.

Manifold

• Ar sample cylinder open, Ar supply valve open, manifold pumping disconnected. This was done when bypass valve connected to air lock pumping some months back.
• Ar supply probably contaminated, maybe missing, i.e. air not Ar
• Disconnect bypass 2.75" VCR flange, add 2.75" tee, reconnect bypass and manifold pump. 
• Turbo pumps down to low 1e-5 in airlock, 14 W turbo, at least no major leak
• Reconnect Ar cylinder/regulator. 
• manifold arrangement bad, no way to isolate Ar supply, need to fix

Electronics

• Electronics start up, software connects, gun to standby, initially ~ 11 mPa, pumps down to zero in ~ hour or less (did not watch)
• Analysis chamber 1.3e-10, after FIG5 pump running a while, ionizer degassed, to 6e-11
• Pressure controller stuck at current limit with software running
• verify cables connected
• verify voltage from ~ 10x10x4 cm USB DAC box on top of 3com switch, voltage 2 V for 20 mPa, etc.
• check output pressure ref from 20-066. Stuck at 10 V, so no pressure control.
• Switch gun briefly from standby to run and back. Now pressure reference works!
• Problem seems to be emission current. Controller cannot maintain 25 mA. 
• Could be result of filament O2 exposure. 
• Can get 20 mA by increasing grid to 180 V from 150 V (range is 120 to 200)
• When emission current out of "green" range, pressure ref goes to 10 V. This may be "fail safe" design...
• Open leak valve 2 full turns, pressure to 4.2 mPa, 
• supply ~ 1 bar relative (regulator), 2 bar absolute
• 2.25 turns, now 33 mPa before controller regulates
• Electronics "click", relay like sound, no clear reason why, its always done this, seems to be associated with cut in ion current.

Test

• 30 degree tilt near center of Cu110 large hole sample holder, excellent auger down to ~ 40 eV. 
• sputter 20 mA "20 mPa" 3 kV 30 sec raster 1x1
• old "scan squares are gone
• Cl peak 180 gone, also O, C reduced
• Cu MVV clear, double peak
• after 6 min C gone

Sample change 13/03/17

In:
AS130220a (source ASEB130311A, cleaved, 40nm Au, VT PBN heater holder)
RSB130317a

Stage Modifications

Background

The "bar" for tip transfer holder is in the center of the sample area and has a significant negative effect on Auger performance, particularly at low voltages.

Also Ion Sputtering is affected.

There are issues with beam current (SCM) measurement. Sometimes this works well, sometimes sample is grounded.

Modifications

Check exact electrical conditions (what metal parts are at what potentials. 

• Each spring clip separately connected to external leads.
• "U shaped" body not grounded at all (except by our previous mod)
• Attachment screws for ceramic clip holders (2x2) and U mount (2x2) isolated from U part, floating.
• Thermal clip hard grounded to chamber
• Clip screws connect to U part.

Changes

• Remove bar and and kapton insulator washer so left clip at U potential.
• Right clip still isolated when no sample plate in place
• Ground all floating screws to U part (tack on grounds with spot welder)
• Add new bar on receiver guide to U part, same side as original but ~ 8 mm back
• Extended back of tip carrier spring to engage new bar, removed most of original bar catch.
• Verify modified tip carrier works for airlock-transfer arm-carousel-stage transfer
• Verify piezo motors

Bakeout

• All turbos running, transfer gate between chambers closed, gun valve open also bypass
• Pump down to 9.5e-6 nano 1.6e-6 prep then start bakeout
• Shut down ion pumps, open gate valves (were closed for up-to-air)
• Start 48 hour bake 5 pm friday 3/8/13
• 3/9/13 10 pm: 6.5e-5 nano, 6.5e-6 prep.
• 3/10/13 2 pm: 3.5e-5 nano, 3.1e-6 prep.

during bake

• Start 5 pm Friday, at noon on Saturday ion gun turbo goes off - no apparent cause. Gate valve closes before bakeout interrupted
• Air temp reaches max at 11 pm Fri, switches off 2 pm Sunday (for 48 hour bake).
• Flange reaches 140 after 5 hours, 180 after 11, cools to 70 C in 11 hours after heat off
• Programmed bake temp is 150 C but air temp goes to 190+/- 5 C, SCA flange reaches 187. 
• Unexplained pressure spike 7:45 am in nano chamber, 6e-9 to 2e-5, recovers by 9 am

Sample change 13/02/25

Out:
AS130221b (Si stripe, 1120sec-grwon Au in prep, VT PBN heater holder) from sample stage

In:
AS130225a (source ASEB130221A, 40nm Au, VT PBN heater holder) to Upper 3

Sample change 13/02/21

Out:
AS130220a (source ASEB130203A, 40nm Au, VT PBN heater holder) from sample stage
VO2 nanowire chip B (w/ Ref VO2 nanowire) from Lower 1 (two window sample holder)

In & Out:
AS130221a (source ASEB130203A, 40nm Au, VT PBN heater holder) to sample stage and out

In:
MSB130221a (MoS2 bulk crystal) & CB130221a (99.999% Cu foil-polished) to Lower 1 (two window sample holder) Mo, S, Cu ref for Auger & XPS.
AS130221b (Si stripe, 1120sec-grwon Au in prep, VT PBN heater holder) to prep chamber

Sample change 13/02/16

Transfer:
CS130213a from sample stage to Lower 1

In:

VO2 nanowire chip B (w/ Ref VO2 nanowire) to sample stage (two window sample holder)

Sample change 13/02/15

Transfer:
CS130213a from Upper 3 to sample stage

In:
AS130215a (source ASEB130203A, 40nm Au, VT PBN heater holder) to Upper 3

Out:
AS130212a (source ASEB130203A, 40nm Au, VT PBN heater holder) from sample stage

Sample change 13/02/12

In:
AS130212a (source ASEB130203A, 40nm Au, VT PBN heater holder) to sample stage

Out:
MSA130201a (normal sample holder w/ c-shaped clamp) from Upper 3

VT PBN sample holder issue

One of screws has been broken when it was unscrewed since the nut is stuck with the bolt thread. This screw should be replaced. Other parts look fine.

Sample change 13/02/05

Transfer:
MSA130201a (normal sample holder w/ c-shaped clamp) from prep chamber to sample stage

Out:
AS130203a (source ASEB130203A, 40nm Au, in-situ PBN heater holder) from Upper 3

Sample change 13/02/04

Transfer:
AS130203a (source ASEB130203A, 40nm Au, in-situ PBN heater holder) from sample stage to Upper 3

In:
MSA130201a (normal sample holder w/ c-shaped clamp) to prep chamber for annealing

Sample change 13/02/03

Out:
AS130201a (in-situ PBN heater holder) from sample stage
MSA130201a (normal sample holder w/ c-shaped clamp) from sample stage for AFM, Raman, PL characterizations

In:
AS130203a (source ASEB130203A, 40nm Au, in-situ PBN heater holder) to sample stage

Sample change 13/02/01

Out:
AS121205a (sample holder) from Lower 1
AS130131a (vac annealing, rectangular window sample holder) from Upper 3
In:
AS130201a (in-situ PBN heater holder) to sample stage
MSA130201a (normal sample holder w/ c-shaped clamp) to sample stage

Sample change 13/01/31

Out:
AS121130f (normal sample holder) from Lower 1
AS121130d (normal sample holder) from Lower 2
AS130125a (in-situ PBN heater holder) from sample stage

In:
AS130131a (in-situ PBN heater holder) to sample stage

SCA Channel 1 not Working

• While taking Auger data, after doing experiments continuously for a week or so, we noticed channel 1 showed zero counts. (Jan 30 2013)
• Red LED was dark at preamp and receiver for Chan 1, other channels normal
• verified CEM HV cable was connected.
• Opened preamp box, 7 modules, 1 per channel. No visible damage, nothing loose. 
• Tried to measure voltages by connecting preamp SHV connectors to Fluke 80K-40 high voltage probe (1 GOhm impedance) 1000:1 voltage divider with Fluke 179 multimeter, hemisphere at 100 V. 
• Got strange values, ~ 240-300 mV but not stable with time. 
• Expected ~ 1.5 V = 1500 V actual. 
• Channel 1 had only 3.4 mV
• With meter connected, channel indicated counts. All 7 similar.
• With multiplier off, swapped channels 1 & 6. preamp cables. Chan 1 still reports no counts, chan 6 OK. Problem not in UHV
• Swapped HV modules in "1127 Multiplier Supply". Problem moved with HV module
• HV module is defective
• Repair/exchange $750, in stock at Omicron US.
• New module installed 2/11/13, works

CEM Gain Adjust

Modified cover of multiplier supply so that the trimpots to set individual CEM voltages are accessible while the cover is closed. This makes CEM voltage adjustment safe and practical. Supply needs to be pulled halfway out of rack.

• Try to balance CEM signals. Pick flat part of spectrum, CAE mode. 
• Chan 2 is low, adjust to max gain. Adjust other channels to ~ match
• Increase supply knob setting to 9.00. No clear plateau in signal vs voltage

Auger imaging parameter optimization

- Sample: Au/Si, AS121130d
- Si peak Auger images were constructed using Auger maps measured at 1616.5, 1635, and 1650 eV.
- Auger maps were measured changing Path energy and Scan time.
- As shown in Fig. 1, optimal path energy for Auger imaging of Si is 160 eV (CRR mode, CAE[eV]/CAE=10).

                                       Fig. 1. Si 1616.5 eV Auger peak height at varying path energy.



- As shown in Fig. 2, as scan time increases, Auger image quality gets better. 21.6 min scan time is enough to get good quality images.

  Fig. 2. Si 1616.5 eV Auger peak height at varying scan time.

Path energy optimization for Nano-auger

- Sample: Si/Au AS121130d
- Auger spectra was measured on (100) Si region at varying Path energy.
- CRR mode from 320 eV to 80 eV
- CAE mode from 70 eV to 5 eV

                                        Fig. 1. Auger spectra measured on Si at varying path energy.

     Fig. 2. Si 1616.5 eV peak intensity vs. path energy and Si 1616.5 eV peak height vs. background ratio.