| Procedure: |
TRL PHOTO
- Get 6" wafers, single polish, and grow about
1/2u thermal oxide.
- HMDS then coat with AZ4620 thick resist, spin 60 sec at
4K rpm.
- Softbake 20 min @ 90C.
- Backside coat w/ same resist/spin parameters as #2 (no
HMDS).
- Softbake 45 min @ 90C.
- Expose in EV1 for 25 sec. you will need to load the
mask with the > 5" chuck, maskholder and loadframe, but
once the mask is loaded, > switch to a 6" chuck
to load and expose the wafer.
- Develop, maybe 3-5 min, in AZ440, mildly agitating
the solution. Rinse.
- Softbake 10 min to dehydrate surfaces.
- Re-coat the back side of the wafer with AZ422, final
spin 30s @ 4K rpm.
- Softbake 10 min.
- Re-coat the front of the wafer, on the outer 3/4" only.
Do NOT let any resist splash or get into the "open" area
in the center of the wafer.
- Softbake 30 min.
TRL ACID-HOOD
- Put wafer into BOE for twice the time it takes to
remove that oxide > thickness, ie if .5 u normally is
removed in 6 minutes, use 12 min.
- Inspect for defects in the open areas. if necessary,
put back in BOE > to remove small oxide remenants
in the open area.
- Piranha strip the wafers of resist.
ICL TMAH-KOH Hood
- Use 6" 25 wafer teflon cassette, green-dot, load
wafers pattern "up" at the H-bar end of the
cassette.
Put 7.5" quartz TMAH bath on wire shelf in water
bath, fill to level. to cover wafers with TMAH, then
cover with poly-pro lid.
Fill water bath with DI, at least 1/2 full, turn power on,
set at 80C. wait 1 hr.
- put wafers in boat into TMAH. etch rate at 80C, 20
- 23u/hr. etch > about 1/2 way thru a typical 610u thick
6" wafer, perhaps 13 - 14 hrs.
- Measure depth in TRL photo-room microscope. use clean
fabwipes to > seperate your wafer, which isn't yet post-TMAH
cleaned, from the > microscope stage. etch further
if required, otherwise:
TRL ACID-HOOD
- Piranha clean etched wafers in same TRL 6" green-dot
cassette the TMAH-etch was done in.
Process completed.
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