Biomedical Engineering Reference
In-Depth Information
In both Equations 4.1 and 4.2, the responses are for the segment AC of the beam where
x
<
a
, (see Figure 4.4). The same approach is used for segment BC of the beam
where
a
<
x
<
l
.
4.1.2 Sensor Fabrication
Sensor fabrication employs, to some extent, procedures that are currently employed in pro-
cess technology used for semiconductor device fabrication, deposition of material layers,
patterning by photolithogrophy, and etching to produce required shapes and patterns.
4.1.2.1 Fabrication of Silicon Part
This sequence is illustrated in Figure 4.6. A (100) double-sided polished silicon wafer
was first RCA cleaned and oxidized (0.5
m thick thermal oxide). A set of four square
patterns was lithographically transferred [13] to one side of the silicon wafer (side b),
which served as alignment marks for positioning the PVDF film. A buffered oxide etchant
(BOE) was used to remove the oxide, after which the exposed alignment pattern was then
etched anisotropically (using PSE-300) for a short period in order to create the alignment
indentations (see Figure 4.6-i).
The wafer was then stripped of all oxide using buffered oxide etch (BOE), RCA clean-
ing, and re-oxidization. Using a double-sided mask aligner, the tooth-like pattern was
lithographically transferred onto the side of the silicon wafer. After patterning the oxide
using BOE, the wafer was etched anisotropically to form the tooth-like structure (see
μ
Side a
(i)
Side b
Alignment mark
(ii)
(iii)
(iv)
Figure 4.6
Fabrication sequence of the silicon part
