the circle draw standard alignment marks, which will be used to
align the mask with the wafer during the photolithography
process (Fig. 1a).
4. Inside the wafer outline, draw the profile of a rectangle measuring 24 Â 50 mm and replicate the structure as per need (see
Note 20).
5. Inside the rectangle, draw two parallel serpentines of 300 μm
thickness, having a circle at each extremity of 1 mm diameter,
which will be used to generate the input and output ports in
the final device (Fig. 1a).
6. Check the layout artwork carefully, zooming throughout the
entire design, to make sure there are no gaps between the
structures.
7. Save your final file in GDSII stream format, which will be used,
by the company, for photoplotting the mask on a plastic film.
8. Cut the plastic film along the square outline of a mask, using a
sharp scalpel and a ruler (Fig. 1a).
9. Superimpose the plastic mask on a 5 Â 5 in. glass mask and
secure it with Scotch Magic tape. The mask is now ready for
photolithography.
3.5 Silicon Wafer
Mold Fabrication
(Photolithography)
1. Turn on the MA/BA6 mask aligner to warm up the UV lamp.
2. Preheat three hot plates at 200
C, 65
C, and 95
C,
respectively.
3. Hold firmly a new silicon wafer with precision wafer handling
tweezers and blow nitrogen gas on it.
4. Place the silicon wafer on the hot plate at 200
C for 30 min to
dehydrate it.
5. Place the wafer on the vacuum chuck of the spin coater and
center it using the precision tweezers.
6. Dispense 2–3 mL of SU8 2150 photoresist on the center of the
wafer and spin at 2000 rpm for 30 s with an acceleration of
300 rpm/s, to obtain a photoresist layer about 250–300 μm
thick (see Note 7).
7. Transfer the coated wafer on a hot plate and soft-bake at 65
C
for 10 min, followed by a second baking at 95
C for 60 min.
8. Transfer the wafer on the vacuum chuck of the MA/BA6 mask
aligner, load the plastic mask secured on the glass mask on the
mask holder, apply the vacuum, and center the wafer and the
mask using the alignment marks through the microscope camera (Fig. 1a).
9. Expose the photoresist-coated wafer to a 12 mW/cm
2 UV
light for 37 s.
10. Transfer the photo-exposed wafer on a hot plate and bake at
65
C for 5 min, followed by a second baking at 95
C for 30 min.
214
Giulia Manina and Neeraj Dhar
align the mask with the wafer during the photolithography
process (Fig. 1a).
4. Inside the wafer outline, draw the profile of a rectangle measuring 24 Â 50 mm and replicate the structure as per need (see
Note 20).
5. Inside the rectangle, draw two parallel serpentines of 300 μm
thickness, having a circle at each extremity of 1 mm diameter,
which will be used to generate the input and output ports in
the final device (Fig. 1a).
6. Check the layout artwork carefully, zooming throughout the
entire design, to make sure there are no gaps between the
structures.
7. Save your final file in GDSII stream format, which will be used,
by the company, for photoplotting the mask on a plastic film.
8. Cut the plastic film along the square outline of a mask, using a
sharp scalpel and a ruler (Fig. 1a).
9. Superimpose the plastic mask on a 5 Â 5 in. glass mask and
secure it with Scotch Magic tape. The mask is now ready for
photolithography.
3.5 Silicon Wafer
Mold Fabrication
(Photolithography)
1. Turn on the MA/BA6 mask aligner to warm up the UV lamp.
2. Preheat three hot plates at 200
C, 65
C, and 95
C,
respectively.
3. Hold firmly a new silicon wafer with precision wafer handling
tweezers and blow nitrogen gas on it.
4. Place the silicon wafer on the hot plate at 200
C for 30 min to
dehydrate it.
5. Place the wafer on the vacuum chuck of the spin coater and
center it using the precision tweezers.
6. Dispense 2–3 mL of SU8 2150 photoresist on the center of the
wafer and spin at 2000 rpm for 30 s with an acceleration of
300 rpm/s, to obtain a photoresist layer about 250–300 μm
thick (see Note 7).
7. Transfer the coated wafer on a hot plate and soft-bake at 65
C
for 10 min, followed by a second baking at 95
C for 60 min.
8. Transfer the wafer on the vacuum chuck of the MA/BA6 mask
aligner, load the plastic mask secured on the glass mask on the
mask holder, apply the vacuum, and center the wafer and the
mask using the alignment marks through the microscope camera (Fig. 1a).
9. Expose the photoresist-coated wafer to a 12 mW/cm
2 UV
light for 37 s.
10. Transfer the photo-exposed wafer on a hot plate and bake at
65
C for 5 min, followed by a second baking at 95
C for 30 min.
214
Giulia Manina and Neeraj Dhar