Page 65 - MEMS Mechanical Sensors

54 MEMS Simulation and Design Tools

nonlinear component arising from the bending of the diaphragm. A straightforward
ANSYS structural analysis was used to achieve a suitable corrugated geometry and
to simulate the diaphragm’s response to applied pressure. The third example, in
Figure 3.13, shows a one-quarter model of a silicon resonant pressure sensor chip
mounted on a glass support and bonded to a stainless steel diaphragm. A thermal
analysis was performed to optimize the height of the glass support in order to mini-
mize the effect of the thermal expansion coefficients of silicon and steel. In addition,
sensitivity of the sensor to applied pressures was also simulated. The strains on the
sensor chip arising from pressure applied to the underside of the steel diaphragm
were applied to a separate model of the resonator. By performing a prestressed
modal analysis, the frequency behavior of the resonator with applied pressure was
determined.

3.2.2.4 MEMS Pro/MEMS Xplorer (MEMScAP)
MEMS Pro and MEMS Xplorer are PC and Unix-based CAD tools, respectively,
and are supplied through MEMSCAP. The MEMS Pro package was developed
originally by Tanner Research, Inc.
The basic MEMS Pro Suite is essentially an L-Edit based layout editor aimed at
the MEMS designer. It contains libraries of standard MEMS components and some
design functions specifically targeted at MEMS. It includes the MEMS Solid
Modeler, which can produce three-dimensional models from the layout using
user-designed fabrication processes. This feature supports both surface and bulk
micromachining processes and enables visualization of the processed MEMS com-
ponent. The model can also be exported into ANSYS, thereby enabling simulation
of the function of the device. This link between the two software packages provides
the complete MEMS CAD package, but it obviously requires the user to have access
to both packages.
The MEMS Pro Verification Suite is the same as the basic suite but with the
addition of a design rule checker, block place, and route function and user program-
mable interface with automated design tools. The next suite up is the MEMS Pro
Design suite, which includes the T Spice Pro module, which enables simulation of
both MEMS and electronic components. This provides an integrated system simula-
tion utilizing an equivalent circuit approach and includes a library of MEMS com-
ponents to facilitate modeling. It also includes a layout versus schematic (LVS)
verification tool, which compares SPICE models extracted from both the layout and
schematic editors. The top of the range MEMS Pro Complete suite also includes
reduced order modeling (ROM) tools, which provide a behavioral model of the
MEMS component from the FE results. This provides a link between the system and
component designers. The Complete suite also accepts CIF files enabling layout files
to be generated from an ANSYS three-dimensional model. ANSYS can also generate
ROM components for use in the MEMS Pro environment. A schematic of the
MEMS Pro Complete suite is shown in Figure 3.14.
Behavioral modeling of MEMS components is available in the MEMS Master
software series developed by MEMScAP. MEMS Master is a prototyping and predi-
mensioning environment that can be used in conjunction with MEMS Pro. Designs
are carried out in the M2Architect tool and simulation is performed by the SMASH