We are developed CAD tools, models and methodologies for
electronics design for circuit operation in extreme environments
with a focus on very low temperature and radiation effects. These
new tools and methodologies help enable NASA, and other researchers
and companies to design next generation electronics. Such
capabilities provide significant improvement in reliability,
performance and lifetime of electronics that are used for space
applications, including satellites and space travel. This is achieved
through the development of novel physics-based modeling techniques
and verified by experiment. The new cryogenic design tools greatly
reduces the chances of error during actual circuit implementation,
and thus reduces the number of design cycles, thereby substantially
decreasing fabrication times and expenses. Models and CAD tools are
relatively inexpensive as compared to fabrication costs, thus the
results of this project provides a very large return on
There has not been a significant effort to design electronics
that operate reliably in outer space. Most of the electronics
design software currently in use do not even give results for
extreme temperature conditions. The details of the semiconductor
physics that occur at cryogenic temperatures simply has not played
a sufficiently large role in electronics design development to
provide the existing knowledge base necessary for robust cryogenic
development. The main difficulties with cryogenic design arise from
changes in carrier mobilities, as well as the carrier freeze-out
phenomena that occur at near absolute zero. These effects must be
fully understood for modern devices, and incorporated accurately
into electronic design tools.
Radiation damage that occurs in outer space also needs to be
more fully worked into the design tool capabilities, especially
for extreme temperature applications. Running numerous experiments
in cryogenic chambers and in the presence of radiation emitting
sources can help NASA alleviate this problem. However, experiments
can not possibly be run for all devices, all circuits, for all
applications and for all operating conditions. Instead, optimal
development and use of design software must be employed to fill in
gaps where exact experiments can not be performed for extreme
Each semiconductor process of interest to NASA must be
characterized and modeled for low temperature applications.
We develop methodology and models for achieving this. To achieve
the described characterization and model development, we take the
following approach that involves experiment, detailed device modeling,
compact device modeling and temperature consistent design:
- Develop detailed device modeling capabilities for transient
operation at cryogenic temperatures.
- Develop detailed device modeling capabilities for AC
(small signal) operation at cryogenic temperatures.
- Develop AC and transient cryogenic device modeling for bulk
and Silicon on Insulator (SOI) devices as well as SiGe.
- Experimentally characterize bulk and SOI devices at low
temperatures by performing cryogenic measurements.
- Extract cryogenic compact models for bulk and SOI
- Adapt compact models and import them into the circuit
simulator SPICE to enable circuit design at cryogenic temperatures.
- Characterize radiation effects in devices and incorporate them
into device simulation and SPICE models.
- Provide cryogenic simulations of key circuit blocks and compare
the simulated results with those obtained on actual ICs.