Introduction: |
The photo-wet station supports several processes
with photoresist developing as the most prevalent process. A
list of chemicals which can be used in the photo-wet station
is compiled in the MATERIALS section. It is strongly advised
that users read the MSDS (Material Safety Data Sheets) before
Using these chemicals to become aware of the proper uses/handling/hazards
of these chemicals. The MSDS sheets for these chemicals can be
found in the copier room on the second floor of Building 39.
The photo-wet station has been approved for restricted
processing with small amounts of solvents and for the developing
of photoresist. No solvents are to be discarded through the
water drain. Used solvents are collected into bottles for
collection by the MIT-Safety Office. It is permissible to
dispose of approved developers and "Semico" cleaners
via the water drain.
The photo-wet is divided into 4 sections, two for metal
lift-off processes, a rinse tank section, and a general use
area. The first metal lift-off section is used for compound
semiconductor processes, and for lift off of gold, tin, and
silver. It contains a variable power ultrasonic tank with
degassing control and time for automatic operation, two hot
plates for solvent cleaning and degreasing, and a DI water
gun.
The second metal lift-off section contains a similar ultrasonic
tank, and is used for silicon based lift-off processes involving
aluminum, platinum, and chromium.
The rinse tank area has dedicated DI rinse tanks, one for
compound semiconductor processes, and the second for silicon
processes.
The fourth area is used for general purpose rinses, etc.
The front control panel has the main power switch and reset switch, four
timers, control switches for the cascade rinse tanks and the dump to
resistivity tank, and the two ultrasonic controllers. A side control
panel contains the two hot plate switches and temperature controllers. |
Procedure: |
MATERIALS:
The following materials have been approved for use in this station.
- Developers: (Tetramethyl Ammonium Hydroxide)
- OCG 934 1:1 for developing of TRL standard resist OCG 825-34cs
AZ 422 MIF for developing of AZ 5214-E
AZ 440 MIF for developing of AZ 4620 Thick Resist
- Solvents:
- Acetone, Methanol, and 1,1,1-Trichloroethane
Cleaning Solution:
Semico (Ammonium Salt cleaning) - Used for Cleaning of
compound semiconductors PROCEDURE: (Immersion Developing)
- Check Equipment Reservations in CORAL to insure that
you reserved the correct machine in the correct facility
for the correct date. Another user may have reservations;
it is your responsibility to honor them, if this is the
case.
- Use the "Engage" command in CORAL for
the equipment that you are about to use; use this command
BEFORE you start the operation. Insure that the correct
facility is set (TRL) and that your lot name is entered
correctly.
Note: The following procedure is for single wafer developing of the
TRL standard photoresist, OCG 825-34cs.
- Choose the proper developer, in this case OCG 934 1:1.
- Rinse appropriate beaker with DI Water and fill with
100-200 cc of developer.
- Immerse wafer into beaker with photoresist side up and
set timer on.
- Slowly move beaker in a "figure 8" pattern
(forward/backward) to agitate liquid developer. You will
see exposed resist dissolving in the developer by the color
changes during developing.
- When large exposed pattern clears, add 10 more seconds
developing time to allow small geometries to open.
- Dump developer into sink and fill beaker/wafer with
DI water at least three times.
- Remove wafer from beaker, place it into a blue teflon
carrier, and rinse wafer in cascade tank for 2 min.
- Transfer wafer in blue wafer carrier into the spin-dryer.
Use 140 sec rinse, 240 sec dry time.
- Inspect wafer under microscope after drying.
- If you are only developing a single wafer, end "Operate
Machine" in CAFE, and proceed to the clean up procedure
described in 8 steps below:
Note: The following procedure is for batch developing of the TRL
standard photoresist, OCG 825-34cs.
- Place wafers in blue teflon wafer carrier.
- Rinse beaker with DI Water and place developer into polypropylene
beaker, so that the developer level will comfortably cover the wafer
carrier.
- Immerse wafer carrier/wafers into beaker and time process as determined
by single wafer development above.
- After developing, immerse carrier/wafers into DI Water cascade tank
and rinse for 2-3 min.
- After 2-3 min. rinse, transfer carrier/wafers into the spin-dryer.
Use 140 sec rinse, 240 sec dry time.
- Inspect wafers under microscope after drying.
- "Disengage" in CORAL.
- Clean up photo-wet station...
- Rinse developing beaker at least 3 times and place it for storage/drying
over the floating counter.
- Return bottles of developers and other chemicals used to the "pass-through".
- Return wafer carriers/holders to proper shelf.
- Rinse counter space. SPECIAL PROCEDURE FOR SOLVENT WASTE HANDLING:
Please follow the following rules for collecting/discarding waste solvents
to avoid potential damage to wafers (and months of work to others) as well
as to prevent the serious threat of gold or other contamination to MTL
wafers/equipment.
- Take short plastic bottle marked as "WASTE SOLVENT".
- Place "SUBSTANCE IDENT" label on bottle
- Open plenum's cover and remove filled bottle, by swinging
bottle and spout sideways. Alarm will sound and stay "on" until
a new bottle is installed.
- Replace bottle with labeled/marked bottle by placing
bottle into spout. Swing bottle/spout into bottle receptacle.
Alarm will silence and solvent left in the line will start
flowing again.
- Leave filled waste solvent bottle in the photo-wet's
plenum. DO NOT return filled waste solvent bottles to the "pass-through" or
leave them in any other place in the laboratory.
Note: Lab staff are responsible for removing waste solvent bottles
from the photo-wet plenum. If you have any questions, please contact
the area specialist or technician for assistance.
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