Biomedical Engineering Reference
In-Depth Information
The current gas supply consists of two capillaries of different diameters that
satisfy the previously mentioned pressure values (30 and 180 mm). Thus, a rapid
pressure drop across a short length is accomplished with a short delay time, which
is about 350 ms in this arrangement. The pressure drop of the sample gas for the
plasma chamber in operation mode is shown in Fig.
18
.
5
Fabrication
MEMS (microelectromechanical systems) are systems with small device sizes of
1-100 mm. They are typically driven by electrical signals. To fabricate such systems
materials like semiconductors, metals, and polymers are commonly used. MEMS
technology fabrication is very cost-efficient. The structures are transferred by pro-
cesses, which are applied to many systems on one substrate or even many of them
simultaneously. The most important fabrication processes are: physical vapor deposi-
tion (PVD), chemical vapor deposition (CVD), lithography, wet chemical etching, and
dry etching. Typical examples for MEMS are pressure, acceleration, and gyro sensors
[
28,
29
] , DLPs [
30
] , ink jets [
31
] , compasses [
32
], and also (bio)medical devices.
The fabrication of the PIMMS-chips is based only on MEMS standard processes.
Figure
19
shows a cross sectional draft of all the MEMS processes which are
necessary to generate the PIMMS. All parts of the mass spectrometer are planar
integrated on one chip, i.e., no individual adjustments of the single components are
needed. The mechanical composition is a glass-silicon-glass“sandwich.” For elec-
trical contacts the metals titanium, nickel and gold are used.
The fabrication process follows the sequence:
1 .
Bottom glass wafer
Deposition of Ni and Au on a glass wafer substrate via sputtering
Patterning of Au layer by photolithography and wet chemical etching
Patterning of Ni layer by photolithography and wet chemical etching
Fig. 19
MEMS process steps
