Difference between revisions of "Lift-Off with DUV Imaging + PMGI Underlayer"
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*Make sure to use a vertical evaporation - EBeam4 or EBeam1. EBeam3 is not vertical. |
*Make sure to use a vertical evaporation - EBeam4 or EBeam1. EBeam3 is not vertical. |
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==Suggested Process for Liftoff== |
==Suggested Process for Liftoff== |
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+ | |De-H2O Bake (eg. 220°C, 1m+) |
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+ | - or - |
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+ | Technics O2 ash (300mT, 100W), 15sec |
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+ | |PMGI-Bake: 220°C, 3min (BrewerSci lift-pin hotplate). |
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+ | |Can just place wafer directly onto hotplate surface. |
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+ | Optionally can use lift-pins & Recipe "'''00 220deg, 3min Vac'''"; |
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+ | --> Enable Vacuum with overhead valve, only for wafer landing and then turn off to prevent sliding. |
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− | *PMGI-Bake: 220°C, 3min (BrewerSci lift-pin hotplate). Can just place wafer directly onto hotplate surface. Optionally can use lift-pins & Recipe "'''''00 220deg, 3min Vac'''''"; Enable Vacuum with overhead valve, only for wafer landing and then turn off to prevent sliding. |
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− | + | |POLOS underside clean: 2000rpm, ACE/ISO/N2 |
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+ | |DI rinse |
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+ | |PEii Technics O2: 30sec (100W/300mT) |
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+ | |'''<u>Metal Evaporation</u>''' |
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+ | (insert steps) |
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+ | |'''<u>Lift-off in NMP</u>''' |
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==Data== |
==Data== |
Revision as of 08:56, 18 May 2020
Developed by Demis D. John, ~2017-2019
This process is intended for Deep-UV Exposure on the ASML DUV Stepper. PMGI is used as the underlayer, which is exposed at the same time as the imaging resist.
This process uses PMGI SF-5 @ 4krpm, which spins to about 130nm (maximum metal thickness = 130nm/3 ≈ 45nm) and undercuts laterally about 130-140nm (minimum gap between metals = (2 x 140nm) + 30nm ≈ 350nm).
Adjust spin speed or switch to a different PMGI formulation to tailor the underlayer thickness to your desired metal thickness.
Tips
Please see our [Bi-Layer Lift-Off Tutorial] to understand the limitations and requirements for good lift-off.
- Remember that gaps in between adjacent metal traces can lift-off during the develop!
- Need underlayer thickness 2x to 3x the desired metal thickness.
- The underlayer will develop laterally from both sides which can lift-off the imaging resist, so:
- Minimum gap between adjacent metals should then be: less than 0.5 * underlayer thickness
- Want at least 30-50nm of underlayer width left to support the imaging resist, so the PR doesn't fall over/collapse.
- Make sure to use a vertical evaporation - EBeam4 or EBeam1. EBeam3 is not vertical.
Suggested Process for Liftoff
De-H2O Bake (eg. 220°C, 1m+)
- or - Technics O2 ash (300mT, 100W), 15sec |
Oxygen ash is faster and more effective |
Spin PMGI SF-5 @ 4krpm (rcp 7) | |
POLOS underside clean: 2000rpm, ACE/ISO/N2 | |
PMGI-Bake: 220°C, 3min (BrewerSci lift-pin hotplate). | Can just place wafer directly onto hotplate surface.
Optionally can use lift-pins & Recipe "00 220deg, 3min Vac"; --> Enable Vacuum with overhead valve, only for wafer landing and then turn off to prevent sliding. |
Spin UV-6-0.8 @ rcp 6 (3.5krpm) | |
POLOS underside clean: 2000rpm, ACE/ISO/N2 | |
Soft-Bake = 135°C, 1min (builtin hotplate) | |
(check underside for particulates) | |
ASML Exposure | |
Default: Exp = 37.5mJ // foc = –0.10 | Try this exposure dose but might need to do a FocArray (smaller Image Distribution eg. 5x5) to find proper exposure. |
PEB = 135°C, 1.5min (built-in hotplate) | |
Dev (300MiF) = 50sec (CRITICAL time) | Use cassette & H2O rinse dish prepared
--> not stirring, instead very slow/gentle lift/drop at various angles or gentle swish just to mix developer slightly. |
DI rinse | Very Gently! Dunk into prepared DI dish, and dump/fill gently 2x. Don’t allow direct hard water to hit PR surface. |
PEii Technics O2: 30sec (100W/300mT) | May increase feature size openings by ~50nm. |
Metal Evaporation
(insert steps) |
EBeam#4 or EBeam#1 with vertical/4-inch holders (not planetary) |
Lift-off in NMP | Facing down or vertical. |
Data
• For PMGI Baked at 220°C for 3min, the PMGI dissolves in AZ 300MIF at a rate of approximately ~600nm/min.
Images / Examples