6 Gold Layer

Gold Layer.
a. Piranha clean if necessary. Otherwise AMI clean.
b. Liftoff photoresist recipe – Gold Pattern
i. YES HMDS Oven.
ii. LOR 5A Photoresist. Programmable Spinner. 500 RPM, 1000 Ramp, 5
s. 3500 RPM, 1000 Ramp, 30 s.
iii. Hotplate. 115 ⁰C, 6 min.
iv. Delay 5 min.
v. 2 µm AZ 1518 Photoresist Recipe without HMDS, up to exposure step.
vi. Karl Suss MA6 Mask Aligner. 365 nm, 7.5 mW, hard contact, 20 µm
alignment gap, 22 s exposure.
vii. Hotplate. 115 ⁰C, 30 s.
viii. MF 26A Developer. 25 s. Add increments of 1 s if not developed
completely.
c. CHA E-Beam Evaporator
Recipe: Gold w/ Tungsten Crucible. Process time: Varies. Depending on recipe
settings deposition rate can reach 1.5 A/s. Deposit as much as possible, at least
200 nm thick.
Notes: May need to require increase of maximum power or else deposition rate
can be zero.
d. Liftoff
i. Prepare multiple Remover PG baths. Heat to upwards of 80 ⁰C. Soak
wafers with agitation. Change to new Remover PG bath after half an
hour. Soak up to another hour with agitation and proceed based on how
much material has been lifted off.
ii. If necessary, use sonicator with wafer in acetone bath, preferably with
wafer in a wafer carrier facing down so that detached particles do not
adhere to top surface.
iii. Notes: Another reported method is to sonicate without solution for 5
seconds prior to first Remover PG soak to create cracks for the solution
to seep through more effectively. The remaining procedure is the same.
Avoid using sonicator unless absolutely necessary as lifted off gold
particles can adhere to the surface and cannot be cleaned off later.