Chalmers University of Technology
Numerical Simulation of
or
simply TCAD
Semiconductor Processes and Devices
Hans Hjelmgren
Microwave Electronics Laboratory
Department of Microtechnology and Nanoscience
MNT 2015; Lecture 3
Chalmers University of Technology
L3: Technology CAD
1.
2.
3.
4.
What is TCAD?
Calibration
Synopsys Sentaurus TCAD
References
MNT 2015; Lecture 3
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Chalmers University of Technology
1. What is TCAD?
TCAD
Process
simulation
Device
simulation
Compact
model
extraction
Circuit
Simulation
MNT 2015; Lecture 3
Chalmers University of Technology
According to Wikipedia
“Technology CAD (or Technology Computer Aided Design, or TCAD) is a
branch of electronic design automation that models semiconductor fabrication
and semiconductor device operation. The modeling of the fabrication is termed
Process TCAD, while the modeling of the device operation is termed Device
TCAD. Included are the modelling of process steps (such as diffusion and ion
implantation), and modelling of the behavior of the electrical devices based on
fundamental physics, such as the doping profiles of the devices. TCAD may
also include the creation of compact models (such as the well known SPICE
transistor models), which try to capture the electrical behavior of such devices
but do not generally derive them from the underlying physics. (However, the
SPICE simulator itself is usually considered as part of ECAD rather than
TCAD.)”
MNT 2015; Lecture 3
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Chalmers University of Technology
(Almost) Everything can be simulated, but
it is not always the best choice since,
• simulations can be extremely time-consuming,
• there may be simpler alternatives, e.g. analytical
expressions, simple measurements,...
• the uncertainty in the obtained results might be too
large,
• or no measurements to check the simulated results
against.
MNT 2015; Lecture 3
Chalmers University of Technology
2. Calibration
Check Software Supplied Models!
C. V. Mouli, J. Vac. Sci: Technol. B, p. 354, 2000.
MNT 2015; Lecture 3
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Chalmers University of Technology
Calibration is difficult and timeconsuming
• Requires knowledge of the exact process flow, device
layout, and how the measurements were done.
• A very accurate calibration is essential for some purposes,
e.g. predicting simulations and positioning of the process
window.
• It is of less importance for other purposes, e.g. failure
analysis, education, prestudies, improved understanding.
• Constant recalibration due to process modifications, new
measurements, and new simulation software.
• Many coefficients in TCAD simulators make it difficult to
determine a unique solution. “Poorly understood
parameters become candidates for tuning.”
MNT 2015; Lecture 3
Chalmers University of Technology
Always make a test with double grid
”If you haven’t tested the
sensitivity of your simulations
to the grid, you haven’t
simulated anything at all”
MNT 2015; Lecture 3
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Chalmers University of Technology
Measurements are not always correct
• SIMS and SRP should be performed and interpreted
accurately.
– A too fast SIMS sputtering resulted in 700 Å instead of 1200 Å
emitter depth.
• Exact process flow.
– Simulated oxide was 400 Å while measured was 700 Å. CVmeasurements indicated 400 Å. The test wafers had not follow
exactly the same flow as the ordinary wafers.
• The spreading in measured data can be significant,
especially at high frequencies due to parasitics, wrong
method (measuring something else), process variations,
etc.
MNT 2015; Lecture 3
Chalmers University of Technology
3. Synopsys Sentaurus TCAD
Examples to
start from
MNT 2015; Lecture 3
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Chalmers University of Technology
MNT 2015; Lecture 3
Chalmers University of Technology
4. References
1.
2.
3.
4.
5.
6.
7.
B. A. Biegel, ”Accuracy counts in modeling TCAD’s future”, IEEE
Potentials, p. 19, 2000.
M. Duane, ”TCAD needs and applications from a user’s perspective”, IEEE
Trans. Electron, p. 976, 1999.
J. Mar, ”The application of TCAD in Industry”, SISPAD, p. 139, 1996.
C. V. Mouli, ”Models and methods: Effective use of technology-computed
aided design in the industry”, J. Vac. Sci: Technol. B, p. 354, 2000.
S. K. Saha, ”Managing technology CAD for competitive advantage: An
efficient approach for integrated fabrication technology development”,
IEEE Trans. Engineering Management, p. 221, 1999.
M. E. Law, “Process modeling for future technologies”, IBM J. Res. &
Dev., vol. 46, pp. 339-346, 2002.
I. Bork, V. Moroz, L. Bomholt, and D. Pramanik, “Trends, demands and
challenges in TCAD”, Mat. Sci. Eng. B, vol. 124-125, pp. 81-85, 1005.
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