TCAD Former Projects
The field of MEMS (micro-electro-mechanical systems) is diverse
in both applications domains and CAD tools required for analysis.
This project cross-cuts other groups at Stanford in materials
science (Bravman) and MEMS applications (Kovacs) along with the
core CAD activities in the Dutton group. The focus of the project
is to develop tools and methodology that capture fabrication details
that directly affect behavior at the subsytems level. Current tools
activities include: geometry modeling, process modeling (emphasis on
materials and stress effects), gridding in support of FEM analysis
and multi-physics behavior modeling (emphasis on coupled electrical
and mechanical dynamic simulation).
Behavior Analysis of RF Devices
The modeling of RF devices and circuits require characterization
of frequency behavior that depends critically on device
non-linearities, for example harmonic (HD) and intermodulation (IM)
distortion. This project uses a new device level harmonic balance
(HB) analysis technique to characterize and model behavior of
several RF power devices (i.e. BJT, LDMOS, GaAs MESFET ...).
Results have demonstrated capabilites to extract critical design
parameters and to correlate them with key technology, layout and
packaging parameters. Another project in the RF area is simulation
and modeling of amplifier front end noise and its correlation with
hot carrier effects.
The prototyping of IC technology and especially for problems
with complex physics, advanced processing and large 3D problems,
requires new tools and numerical methods---both computationally
and for visualization of complex results. This project brings
together a heterogenous set of TCAD tools (ALAMODE and PROPHET)
within the context of shared parallel computational resources
(i.e. the "para" in ParaSCOPE) and in support of internet use
and visualization. Advances in rapid prototyping of new
physical models, applications to leading edge IC technology
development (and characterization) as well as a range of supporting
software issues are being pursued.
Advanced Process Simulation using A Layered Model Development
ALAMODE), PROPHET (Bell Labs) and other FEM-based tools
There are a range of new and advanced physical models needed for
deep submicron IC technology. This project, a companion to the
ParaSCOPE (which is more system level and application driven), addresses
the details of tool developments that are needed for such advanced
physical modeling. Three distinct classes of tools are being
developed, compared and made to be inter-operable (when possible
and useful). ALAMODE uses a deeply object-oriented implementation
of a PDE "engine" with emphasis on reactive-diffusive equations.
The PROPHET tool, being collaboratively developed with Bell Labs,
is targeted as a combined process/device simulator with modular
"scripting" of new models at an operator level. Other work in
FEM-based stress anaylsis uses an Eularian formulation that comes
from the computational mechanics community.
Device Modeling of Electrostatic Discharge (ESD)
There are increasing demands on devices and circuits at the periphery
of ICs due to reliabilty issues such as latchup, substrate noise and
electrostatic discharge (ESD). All of these problems require modeling
of distributed effects inside the substrate and careful consideration
of the boundary conditions and lumped circuit elements that represent
both the circuit schematics as well as parasitic effect. This project
seeks to apply advanced 2D and 3D device modeling, including mixed-level
circuit/device as well as electrical/thermal simulations, to characterize
ESD and support innovations that help prevent it. This project is
partially supported by SRC and cross-cuts Mechanical Engineering (Goodson)
and Electrical Engineering (Dutton).
Stress Analysis of Shallow Trench Isolation (STI)
There is a rapid shift in isolation technology for ICs from the
traditional LOCOS process to STI in order to increase packing density
for deep submicron processes. However, there are many challenges
related to stress, materials/process dependences and electrical
behavior (especially leakage). This project is targeted to develop
and apply new FEM-based software (see ParaSCOPE and ALAMODE project
descriptions) specifically to the area of stress analysis for STI.
The project is partially supported by SRC (experimental only) with
major software efforts supported through DARPA and CIS sponsor
funding. The goal is to demonstrate new computational models for
stress and to quantify the materials dependences and applications
in practical technology demonstrations.
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