Biomedical Engineering Reference
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(a)
(b)
1 µ m
1 µ m
Cl 2 RIE
O 2 RIE
(c)
(d)
HF etch
1 µ m
1 µ m
FIGURE 12.11 Outline of the templating procedures for fabricating antireflective silicon pillar arrays by using spin-
coated, non-close-packed, monolayer colloidal crystal as template. Adapted from Ref. 105 .
12.3.1.2 Dry-Etched Single-Crystalline Silicon
Moth-Eye Antireflection Coatings
To fabricate periodic arrays of moth-eye pillars
with high aspect ratio, a versatile dry-etching-
based templating nanofabrication technology
has been developed [105, 109] . The outline of
the templating procedures for patterning moth-
eye pillar arrays on single-crystalline silicon
substrates is shown in Figure 12.11 . The spin-
coating technique [99] is first used to gener-
ate non-close-packed colloidal monolayers of
hexagonally ordered silica particles on silicon
wafers ( Figure 12.11 a). These particles are then
used as etching masks during a chlorine-RIE
process (5 mTorr pressure, 20 sccm chlorine flow
rate, and 80 W) or a SF 6 -RIE process (40 mTorr
pressure, 26 sccm SF 6 , 5 sccm O 2 , and 25 W).
Because the etching rate of silica is much lower
than that of silicon under above-RIE conditions
[112] , silica particles protect silicon immediately
underneath them from being etched, resulting
in the formation of pillar arrays directly on the
silicon surface ( Figure 12.11 b). Once the silicon
pillars are deep enough, the templating silica
spheres can be removed by dissolving in a 2%
hydrofluoric-acid aqueous solution.
 
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