4. Metallization can be processed by any other vacuum coating
equipment. Additionally, evaporation is another standard metallization method. If you want to fabricate more than 6 glass
wafers for one time, evaporation would help in lowering
the cost.
5. Other pulse power supplies with output capability over
5000 Hz pulse and 1 ampere can be used for electroplating.
6. There are many other commercial microneedle rollers products, and we recommend common Derma Roller System
600 series products for its low cost and convenience.
7. Alternative high-voltage pulse generator capable of producing
5–100 V square wave pulse with 5–20 ms pulse width and 1–5 s
interval between pulses is workable.
8. The adhesion between gold and Parylene is not strong.
Chrome or titanium layer beneath gold can enhance adhesion
to protect gold layer from detachment.
9. The suboptimum resist adhesion may cause peeling of the resist
as a consequence in the next steps. The substrate pretreatment
with HMDS promoter can improve that between the resist and
the wafer surface efficiently.
10. Recommended recipe: Spin at 500 rpm for 10 s and 2400 rpm
for 60 s; Soft-bake at 98
C with hotplate for 15 min; Exposure
1500 mJ/cm
2
; Development in AZ 400 K developer for 3 min;
Postbake at 130
C for half hour.
11. If there is no RIE equipment, any oxygen plasma cleaner which
has power greater than 20 W is acceptable.
12. In our lab, as a reference, the power of oxygen plasma machine
is 250 W, and the cleaning costs 30 s.
13. This step is very important for electroplate. The surface of the
seed layer to be plated must be very clean. Electroplate process
requires sufficient residual-free development for that the thin
and invisible residual and adhesion promoter HMDS may
highly deteriorate the contact between gold seed layer and
deposit liquid.
14. Recommended condition: duty ratio ¼ 0.1 (2 ms: 18 ms);
electric current density: 0.6~0.9 A/dm
2 .
15. Closely monitor the electroplate process. Once there is black
dot generated on the electrode, the current density need be
suitably reduced. Measure the thickness of the deposited metal
every 20 min. If no bulk of gold comes into being, the current
should be increased.
16. Successful electroporation requires a sufficient electric field,
thus small distance of electrodes means low voltage. But in
the meantime, small distance also can induce electric spark or
110
Dong Huang et al.
equipment. Additionally, evaporation is another standard metallization method. If you want to fabricate more than 6 glass
wafers for one time, evaporation would help in lowering
the cost.
5. Other pulse power supplies with output capability over
5000 Hz pulse and 1 ampere can be used for electroplating.
6. There are many other commercial microneedle rollers products, and we recommend common Derma Roller System
600 series products for its low cost and convenience.
7. Alternative high-voltage pulse generator capable of producing
5–100 V square wave pulse with 5–20 ms pulse width and 1–5 s
interval between pulses is workable.
8. The adhesion between gold and Parylene is not strong.
Chrome or titanium layer beneath gold can enhance adhesion
to protect gold layer from detachment.
9. The suboptimum resist adhesion may cause peeling of the resist
as a consequence in the next steps. The substrate pretreatment
with HMDS promoter can improve that between the resist and
the wafer surface efficiently.
10. Recommended recipe: Spin at 500 rpm for 10 s and 2400 rpm
for 60 s; Soft-bake at 98
C with hotplate for 15 min; Exposure
1500 mJ/cm
2
; Development in AZ 400 K developer for 3 min;
Postbake at 130
C for half hour.
11. If there is no RIE equipment, any oxygen plasma cleaner which
has power greater than 20 W is acceptable.
12. In our lab, as a reference, the power of oxygen plasma machine
is 250 W, and the cleaning costs 30 s.
13. This step is very important for electroplate. The surface of the
seed layer to be plated must be very clean. Electroplate process
requires sufficient residual-free development for that the thin
and invisible residual and adhesion promoter HMDS may
highly deteriorate the contact between gold seed layer and
deposit liquid.
14. Recommended condition: duty ratio ¼ 0.1 (2 ms: 18 ms);
electric current density: 0.6~0.9 A/dm
2 .
15. Closely monitor the electroplate process. Once there is black
dot generated on the electrode, the current density need be
suitably reduced. Measure the thickness of the deposited metal
every 20 min. If no bulk of gold comes into being, the current
should be increased.
16. Successful electroporation requires a sufficient electric field,
thus small distance of electrodes means low voltage. But in
the meantime, small distance also can induce electric spark or
110
Dong Huang et al.