SPR 955

SPR 955 is an I-line series of photoresists developed by microchem, it's similar to SPR 220 but is formulated for thinner viscosities and higher resolution. We've been able to consistently get 500nm gratings in 0.97µm of SPR 955 in the stepper, on silicon. The 0.97µm thickness was chosen because it's one of the peaks listed in the datasheets swing curve.

Processes

SPR 955 (0.97µm)

Vapor prime wafer with HMDS
Spin 0.97µm in ACS, CEE 200X #1 or CEE 100CB
Bake at 100°C for 90 sec
Verify thickness if possible, for thin resists small thickness variations drastically change the necessary exposure dose.
Expose

Material	Stepper	Contact Aligner
Silicon	0.3 sec	5 sec
500nm SiO2	?	?

Bake at 110°C for 90 sec
Develop
- ACS 200 cluster tool - AZ 300 for 25 sec
- CEE Developer - AZ 726 45 sec single puddle

Notes: When photoresist is this thin the swing curve will have a larger effect; small thickness variations will have a larger change in the necessary exposure. Also at the end of the process you will have closer to .9-.94µm of resist.

These gratings are on silicon and exposed via the stepper.