Karl Suss Mask Aligner
Procedure No.:
Procedure Title:
Revision:
Group:
Physics CR-???
Karl Suss Mask Aligner
1
Date:
Author:
23rd March 2009
Karl Süss Mask Aligner
The mask aligner allows the user to do photolithography on thin substrates with either
positive or negative photoresists. Under optimum conditions it is possible to achieve onemicron feature sizes. It is a very very very expensive instrument!
Do not attempt to use the aligner to cure polymer samples, you will get better results with the
other UV lamps and YOU WILL BE BANNED.
Operation procedure
1. Make sure that the dry nitrogen gas line is on outside the cleanroom. The aligner also
requires the compressed air and vacuum lines to be operational.
2. On the right hand side of the aligner’s microscope assembly is a vertical glass tube,
this is the nitrogen gas indicator. There are switches on the box next to this for the
nitrogen gas, switch these all on and the ball inside the tube should rise up. If this
does not happen then check the nitrogen gas tap on the ceiling, if that is off then
notify the person in-charge to come and set it correctly it for you. DO NOT ALTER
THE GAS TAPS YOURSELF.
3. The ball on the nitrogen gas monitor should now be floating above the collar around
the tube. If you are unsure about this, switch the mask aligner on and if the nitrogen
alarm light flashes (maybe accompanied by a beeping sound) then the gas is not
okay. YOU CANNOT PROCEED WITHOUT THE NITROGEN.
4. Leave the nitrogen for about one minute to purge the lamp.
5. Making sure that the mask aligner is off first (there is an interlock to prevent power
surge damage), switch on the UV lamp control box and watch the self-test. It is
normal for the FIRE message to flash a few times but it should go away after 10
seconds – if it does not stop, then switch it off and call the person in-charge. The
lamp is okay when the ready message is up.
6. Press the LAMP START button. The lamp requires a short time to become
operational but 20 minutes to 1 hour to fully settle – you only need to leave it this long
if you are working with feature sizes below about 5 microns. It consumes nitrogen
quickly, so try to avoid leaving it on for too long.
7. Switch on the mask aligner. The three pressure gauges on the top of the box to the
right of the microscope should move roughly in-line with the marker pen lines drawn
on the glass, if not then contact the person in-charge DO NOT ALTER THEM –
EACH GAS COMPONENT COSTS AT LEAST ONE THOUSAND POUNDS EACH!
8. Switch on the microscope illuminator by the switch on the rear of the unit.
9. Undo the thumbscrew that holds the mask holder in place and slide the holder out of
the unit. Place it on the table with the vacuum grove facing upwards.
10. Take the mask you require and place it with the chromed side facing upwards from
the desk. Make sure it covers over the entire groove on the holder.
11. Press the VACUUM MASK button, this should affix the mask to the holder – check
this before proceeding!
12. Slide the holder back into the mask aligner and tighten the thumbscrew.
13. Focus the microscope on your mask pattern. Use the big lever to move the
microscope around – the two buttons activate the air assist, one give horizontal
movement and the other vertical.
14. Make sure the contact lever is facing towards you and the separation lever is not in
the separation position. Neither the CONTACT nor the SEPARATION indicator lights
should be lit.
15. Slide the substrate tray out from the side and then use the rotation micrometer to
straighten out the tray.
16. Position your substrate onto the tray in a position when it is as close to lining up with
the desired mask area as possible. Check by sliding the tray in.
17. While watching though the microscope: Turn the contact lever away from you and
watch your sample rise towards the mask, you should make the first physical contact
with the mask when you have turned the lever 75-80% of the way over. A good way
to check is to use the left/right micrometer to “dither” the substrate back and forth –
when your sample stops moving, you are touching the mask!
The CONTACT indicator should illuminate. If the SEPARATION indicator comes on,
move the separation level to the opposite position (the indicator should switch off)
and you need to lower your substrate and repeat this step again.
IMPORTANT: THERE IS A VERY LIMITED VERTICAL TRAVEL RANGE!! IF YOU
ADJUST THE up/down MICROMETER TOO FAR DOWN THE MECHANISM WILL
FALL APART. IF THIS HAPPENS, CONTACT THE PERSON IN-CHARGE! IF YOU
ATTEMPT TO FIX THIS YOURSELF YOU CAN CAUSE THOUSANDS OF POUNDS
OF DAMAGE!
18. To align your sample, move the separation lever so the SEPARATION indicator lights
up. This lowers your sample and allows small adjustments. If you cannt move your
sample in the separation mode then the substrate is too high, or you have not baked
you resist sufficiently. It is unwise to continue until you have adjusted the height
properly!
19. Take care over the alignment, it can take many adjustments. Move the microscope
around to check the alignment over your entire sample before proceeding.
20. When done, move the separation lever back into CONTACT.
21. Set your exposure time on the timer on the bottom right of the aligner controls. For
Shipley S1815 resist, 4 seconds should be adequate.
22. Check that the UV lamp control is set to the correct intensity control. You may use the
CI1 or CI2 setting to keep a constant intensity. They work by sensing the UV intensity
at two different wavelengths (it does not change the wavelength of light!). Check the
log-book next to the instrument for up-to-date details. The CP setting supplies a
constant electrical power to the lamp.
23. If you are using CI1 or CI2, it may be a good idea to “train” the feedback loop by
running the aligner exposure without your substrate in it first.
24. With the CONTACT indicator on, press EXPOSURE. If after about five seconds the
microscope hasn’t lifted up, gently lift it until it unsticks and it should be okay after
that. If unsure, contact the person in-charge.
25. The microscope should lift clear of the sample and the exposure housing will slide
forwards. If it is having trouble then you should report this to the person in-charge –
meanwhile it is okay to gently help it by pulling the housing forwards.
26. Once in-position the exposure occurs automatically. DO NOT LOOK AT THE LIGHT!
The housing will return to its starting position automatically.
27. Pull the contact lever towards yourself and then slide out the substrate stage and
remove your sample.
28. When you have finished with your mask, undo the thumbscrew and slide out the
mask holder. Place it mask side up on the desk and then press VACUUM MASK to
remove the suction.
29. Replace the mask holder and tighten the screw.
30. When finished, switch off the mask aligner power first (important!).
31. Then switch of the UV lamp and illuminator control boxes.
32. Switch off the gas switches on the control box – DO NOT LEAVE THE NITROGEN
FLOWING!
33. REPLACE THE SOFT COVER OVER THE ALIGNER!
34. Make a record of your use in the log book – this will help you and others who wish to
use the equipment.