Biomedical Engineering Reference
In-Depth Information
(c) Roughen the surface of the stainless steel, soaking it in a 2:8:90
solution of HF, HNO
3
, and water. Wash at room temperature
with ultrasonic cleaning.
(d) Implement the activation treatment on the surface of the
stainless steel. Soak the stainless steel in a 10% sulfuric acid
solution. Use ultrasonic cleaning to remove the surface oxide
layer.
(e) Treat the stainless steel with nitrogen and dry with heat to
remove moisture.
(f) Coat the stainless steel with suitable photo-resistant
material. Refer to the previous section to select the correct
positive/negative photo-resistance. If desired, the thickness
of the photo-resistant material mold can be increased after
completion.
(g) Soft bake the photo-resistant material. The purpose of the
soft bake process (which has been described in the previous
section) is to remove the solvent in the photo-resistant
material, and is an important factor in controlling adhesion,
exposure, and imaging parameters.
(h) If the photo-resistant stainless steel plated has been properly
prepared, place the mask design on top and expose it with
a 365 nm i-line light source, so the pattern of the mask will
be transferred to the substrate. The exposure produces
macromolecule polymerization (positive photo-resistance)
and decomposition (negative photo-resistance) to achieve the
transfer the mask pattern.
(i) Once the exposure is complete, the development process
removes some unnecessary photo-resistant material. Negative
photo-resistance will not wash away while positive photo-
resistance development will be exposed as part of the wash,
leaving behind the pattern that was not exposed.
(j) Finally, the hard bake procedure removes the remaining photo-
resistant solvent and moisture. This condenses the photo-
resistant resin bonding compounds and increase the photo-
resistant heat stability and adhesion so the mask pattern can
be protected.
Once the processing of the stainless steel substrate in complete,
completing above steps lithography process results in the appearance
of the lithography pattern, as shown in the Fig. 6.3. This process is
followed by the electrodeposition process.
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