Chapter 6.12
Veeco 401 Vacuum System
(V401)
Veeco 401 Vacuum System (v401)
This document has specific
information about Veeco (thermal evaporation system).
The Veeco 401 is a high vacuum
thermal evaporation system. Only materials with a relatively low vapor pressure
should be evaporated in this system in order to avoid contamination problems.
Pump down and venting of the Veeco 401 are automatic. There are two high
current feed-throughs allowing multiple, sequential evaporations. An Inficon
XTM thickness and rate monitor allows direct read-out in A/sec for rate and in
kA for thickness. The shutter is manually controlled.
How
a high vacuum system works: http://www.genvactech.com/Vac_Technologies/Vac_Tech_Article_1.htm
In general, materials with
high vapor pressure should not be used in a vacuum system because they
contaminate the system. (e.g. Sulfur - 10E-6 Torr at 19ºC). If you
want to evaporate an unusual material, e-mail v401@silicon.
6.1
Do not use tapes,
plastics or wax without discussing their use with the Process Manager. Exception:
Kapton tape is permitted.
6.2
Do not scratch the base
plate.
6.3
Do not leave the vacuum
system until you are certain the bell jar is seated correctly and the system is
roughing down properly.
6.4
Do always wear clean
polyethylene (clear plastic) gloves when working inside the bell jar.
6.5
Do make sure cooling
water is flowing for the crystal monitor.
6.6
Do wait for at least 20
minutes (depending on temperature and duration of evaporation) before venting
the system to allow materials in the bell jar to cool. Failure to sufficiently
cool metal evaporation sources may result in the formation of metal oxides,
which may be a health hazard and mobile.
6.6.1
Dispose of old boats
and chrome rods in the red sharps disposal situated on the NRC.
6.6.2
Do not use an N2 gun to
clean the v401. Use a vacuum hose to prevent metal particles from being blown
around.
7.0
Statistical/Process
Data
N/A
8.0
Available
Processes, Gases, Process Notes
The
following metals are currently allowed in the v401: Al, Ag, Au, Co, Cr, Cu, Fe,
Hf, Mg, Nb, Ni, Mo, Pd, Pt, Ru, Ti, V, Zr.
9.0
Equipment
Operation
A large majority of the
Veeco operating procedure must be learned by watching a qualified user
demonstrate the machine's operation. Be sure to observe its use through at
least two evaporations. Once you have become familiar with the evaporator set
up, follow the checklist/procedures below.
9.2 Check cooling water to crystal monitor.
9.3
Make sure ion gauge is
turned off first, then turn switch to Vent position. Venting takes ~ 1
minute. Wait for TCA gauge to level off (at ~500 Torr) before opening bell jar.
9.4 Open bell jar by pressing up button on yellow controller.
9.5
Attach electrodes and source
boat(s) and load source. Place chimney, shutter, sample holder and sample. Turn
on and check quartz crystal monitor. Change crystal if necessary. A spare
should be available for the v401. Replacement crystals are available from the
office and are not recharged. Lab members are responsible for crystal changes
and should make sure a spare is also available for the next user.
Note: Check that copper feed-throughs and straps are
free of oxide to insure good conductivity. Use Scotch-brite to clean if
necessary.
9.6
Close bell jar by
pressing the down button on yellow controller.
9.7
Turn switch to Pump
position. Chamber will pump down to ~200 mTorr and automatically switch to the
cryo pump.
9.8
After the cryo pump has
started, turn on the ion gauge. If it reads less than 10-5 Torr,
turn on the degas. This will turn off the ion gauge. Degas the gauge for 5 or
10 minutes. Never allow the degas to remain on longer than 20 minutes.
9.9
Enter density and Z-ratio
values for your evaporation metal on V401 crystal monitor.
9.10
Change metal bars to
select correct electrode/boat if necessary. Be sure power supply is off!
9.11
When desired base
pressure is achieved, turn the transformer breaker on. The red light next to the
current (I) meter should illuminate. If it does not, contact staff for possible
fuses replacement. Use the variable power supply to heat your source. It is
usually good to heat your source at a low setting for about 30 seconds before
evaporating to remove adsorbed water vapor.
9.12
Evaporate your source.
(~150 amps needed for aluminum.). It is best to leave the shutter closed for
the first few seconds of the evaporation, to burn off the dirty outer coating
of your metal source. Then open the shutter, zero crystal monitor, and watch
thickness on the monitor.
9.13
Close shutter and turn
power off when you reach the desired thickness. Let system cool down for 15-20
minutes.
9.14
Turn ion gauge off!
9.15
Turn switch to Vent
position to vent chamber as before. Remove your wafer, boats, and any leftover
evaporation metal.
9.16
Leave all electrodes
and the chimney inside the chamber when finished. Materials kept inside will
not absorb water and the Veeco will pump down quicker.
9.17
Lower the bell jar and
set the switch to Pump. Make sure that
the system crossed over to Hi Vac before leaving. Turn on ion gauge and disable
V401 on Wand.
10.0 Troubleshooting Guidelines
10.1
Vacuum System
Lock-Up (if pump/vent knob is
non-responsive)
10.1.1
Open front panel door
of the HSD vacuum system controller.
10.1.2
Locate the power
ON/Manual switch inside top left corner and switch it down to off and back
up to ON
10.1.3
DO NOT change the
position to any other switches inside this controller
The cryo will be regenerated
by staff when the operating temperature exceeds 16K or if the base pressure is
above 2 x 10-6 following a 4 hour pump-cycle. Lab members should
report a FAULT for these conditions.
11.0 Figures & Schematics
N/A
12.0 Appendix
12.1 Rotating Sample Stage
Thickness uniformity of ±5%
can be achieved in the v401 using the rotating sample plate. This sample plate may be found in the glass
cabinet next to the spare chimneys in room 432a. The following procedure outlines the installation and use of this
rotating sample mount.
1)
Make sure that the
bearing rotates easily and is free of debris.
2)
Firmly seat the
universal joint on the outer post on the drive arm.
3)
Wafers may be mounted
to the sample plate by affixing Kapton tape to the back of the wafer and
attaching this to the sample plate.
The sample plate may be released from the drive shaft by loosening the
set screw on the back of the sample plate.
4)
Remove the shutter and
chimney from the vacuum chamber.
5)
Install the boat and
source material as usual.
6)
Securely mount the base
plate of the rotating holder to the crystal monitor support arm with a
c-clamp. Note: Be sure that you do not
crush the crystal monitor water lines while securing the plate.
7)
Attach the drive
motor’s electrical lead to the front most thermocouple feed through on the
right hand side of the camber.
8)
Attach the yellow power
cable located under the chamber baseplate of the v401 to an external power
supply capable of sourcing 20V. Contact
the Microlab staff for a suitable power supply. The motor should turn with an applied voltage of 14-15V.
9)
Verify that the motor
runs and that the polarity is correct.
10)
Pump down the chamber
and deposit films as normal while rotating the sample plate. The film thickness will be approximately five
times thicker than the value reported by the crystal thickness monitor. Note that there is no shutter in the system
during the deposition.
11)
Return the sample stage
to the glass cabinet when finished.