@COMMENT{{{This file has been generated by bib2bib 1.75}}
@COMMENT{{{Command line: bib2bib -ob Publications-journals.bib -c '$type = "ARTICLE" and exists abstract' /Users/Clemens/Documents/Curriculum-Vitae/Publications.bib}}
@ARTICLE{ringhofer2008multi-scale,
AUTHOR = {Christian Ringhofer AND Clemens Heitzinger},
TITLE = {Multi-Scale Modeling and Simulation of Field-Effect Biosensors},
JOURNAL = {ECS Transactions},
VOLUME = 14,
YEAR = 2008,
MONTH = AUG,
URL = {},
PDF = {},
ABSTRACT = {},
NOTE = {\textit{Accepted for publication}}
}
@ARTICLE{heitzinger2008modeling,
AUTHOR = {Clemens Heitzinger AND Rick Kennell AND Gerhard Klimeck AND Norbert Mauser AND Michael McLennan AND Christian Ringhofer},
TITLE = {Modeling and Simulation of Field-Effect Biosensors ({BioFETs}) and Their Deployment on the {nanoHUB}},
JOURNAL = {J. Phys.: Conf. Ser.},
VOLUME = 107,
PAGES = {012004/1--12},
YEAR = 2008,
DOI = {doi:10.1088/1742-6596/107/1/012004},
URL = {http://www.iop.org/EJ/abstract/1742-6596/107/1/012004},
PDF = {http://www.iop.org/EJ/article/1742-6596/107/1/012004/jpconf8_107_012004.pdf},
ABSTRACT = {BioFETs (biologically active field-effect transistors) are
biosensors with a semiconductor transducer. Due to
recent experiments demonstrating detection by a
field effect, they have gained attention as
potentially fast, reliable, and low-cost biosensors
for a wide range of applications. Their advantages
compared to other technologies are direct,
label-free, ultra-sensitive, and (near) real-time
operation. We have developed 2D and 3D multi-scale
models for planar sensor structures and for nanowire
sensors. The multi-scale models are indispensable
due to the large difference in the characteristic
length scales of the biosensors: the charge
distribution in the biofunctionalized surface layer
varies on the Angstrom length scale, the diameters
of the nanowires are several nanometers, and the
sensor lengths measure several micrometers. The
multi-scale models for the electrostatic potential
can be coupled to any charge transport model of the
transducer. Conductance simulations of nanowire
sensors with different diameters provide numerical
evidence for the importance of the dipole moment of
the biofunctionalized surface layer in addition to
its surface charge. We have also developed a web
interface to our simulators, so that other
researchers can access them at the nanohub and
perform their own investigations.}
}
@ARTICLE{heitzinger2007finite,
AUTHOR = {Clemens Heitzinger AND Christian Ringhofer AND Siegfried Selberherr},
TITLE = {Finite Difference Solutions of the Nonlinear {Schrödinger} Equation and their Conservation of Physical Quantities},
JOURNAL = {Commun. Math. Sci.},
VOLUME = 5,
NUMBER = 4,
PAGES = {779-788},
MONTH = DEC,
YEAR = 2007,
URL = {http://www.intlpress.com/CMS/p/2007/issue5-4/CMS-5-4-A2-Heitzinger.pdf},
PDF = {http://www.intlpress.com/CMS/p/2007/issue5-4/CMS-5-4-A2-Heitzinger.pdf},
ABSTRACT = {The solutions of the nonlinear Schrödinger equation are of
great importance for ab initio calculations. It can
be shown that such solutions conserve a countable
number of quantities, the simplest being the local
norm square conservation law. Numerical solutions of
high quality, especially for long time intervals,
must necessarily obey these conservation laws. In
this work we first give the conservation laws that
can be calculated by means of Lie theory and then
critically compare the quality of different finite
difference methods that have been proposed in
geometric integration with respect to conservation
laws. We find that finite difference schemes derived
by writing the Schrödinger equation as an
(artificial) Hamiltonian system do not necessarily
conserve important physical quantities better than
other methods.}
}
@ARTICLE{heitzinger2007effective,
AUTHOR = {Clemens Heitzinger AND Christian Ringhofer},
TITLE = {An Effective Quantum Potential for Particle-Particle Interactions in Three-dimensional Semiconductor Device Simulations},
JOURNAL = {Journal of Computational Electronics},
VOLUME = 6,
NUMBER = 4,
PAGES = {401-408},
YEAR = 2007,
DOI = {10.1007/s10825-007-0148-4},
URL = {http://dx.doi.org/10.1007/s10825-007-0148-4},
PDF = {http://www.springerlink.com/content/x2m56hq080724k05/fulltext.pdf},
ABSTRACT = {The classical Coulomb potential and force can be calculated
efficiently using fast multi-pole methods. Effective
quantum potentials, however, describe the physics of
electron transport in semiconductors more
precisely. Such an effective quantum potential was
derived previously for the interaction of an
electron with a barrier for use in particle-based
Monte Carlo semiconductor device simulators. The
method is based on a perturbation theory around
thermodynamic equilibrium and leads to an effective
potential scheme in which the size of the electron
depends upon its energy and which is
parameter-free. Here we extend the method to
electron-electron interactions and show how the
effective quantum potential can be evaluated
efficiently in the context of many-body
problems. Finally several examples illustrate how
the momentum of the electrons changes the classical
potential.}
}
@ARTICLE{heitzinger2007computational,
AUTHOR = {Clemens Heitzinger AND Gerhard Klimeck},
TITLE = {Computational Aspects of the Three-Dimensional Feature-Scale Simulation of Silicon-Nanowire Field-Effect Sensors for {DNA} Detection},
JOURNAL = {Journal of Computational Electronics},
VOLUME = 6,
NUMBER = {1-3},
PAGES = {387-390},
YEAR = 2007,
DOI = {10.1007/s10825-006-0139-x},
URL = {http://www.springerlink.com/content/k888322550q77216/?p=3775349bb29e4462a47731b834eecf5b&pi=2},
PDF = {http://www.springerlink.com/content/k888322550q77216/fulltext.pdf},
ABSTRACT = {In recent years DNA-sensors, and generally biosensors, with
semiconducting transducers were fabricated and
characterized. Although the concept of so-called
BioFETs was proposed already two decades ago, its
realization has become feasible only recently due to
advances in process technology. In this paper a
comprehensive and rigorous approach to the
simulation of silicon-nanowire DNAFETs at the
feature-scale is presented. It allows to investigate
the feasibility of single-molecule detectors and is
used to elucidate the performance that can be
expected from sensors with nanowire diameters in the
deca-nanometer range. Finally the computational
challenges for the simulation of silicon-nanowire
DNA-sensors are discussed.}
}
@ARTICLE{heitzinger2007monte,
AUTHOR = {Clemens Heitzinger AND Christian Ringhofer AND Shaikh Ahmed AND Dragica Vasileska},
TITLE = {{3D} {Monte-Carlo} Device Simulations Using an Effective Quantum Potential Including Electron-Electron Interactions},
JOURNAL = {Journal of Computational Electronics},
VOLUME = 6,
NUMBER = {1-3},
PAGES = {15-18},
YEAR = 2007,
DOI = {10.1007/s10825-006-0058-x},
URL = {http://www.springerlink.com/content/k5550m151310078v/?p=3775349bb29e4462a47731b834eecf5b&pi=0},
PDF = {http://www.springerlink.com/content/k5550m151310078v/fulltext.pdf},
ABSTRACT = {Effective quantum potentials describe the physics of
quantum-mechanical electron transport in
semiconductors more than the classical Coulomb
potential. An effective quantum potential was
derived previously for the interaction of an
electron with a barrier for use in particle-based
Monte Carlo semiconductor device simulators. The
method is based on a perturbation theory around
thermodynamic equilibrium and leads to an effective
potential scheme in which the size of the electron
depends upon its energy and which is
parameter-free. Here we extend the method to
electron-electron interactions and show how the
effective quantum potential can be evaluated
efficiently in the context of many-body
problems. The effective quantum potential was used
in a three-dimensional Monte-Carlo device simulator
for calculating the electron-electron and
electron-barrier interactions. Simulation results
for an SOI transistor are presented and illustrate
how the effective quantum potential changes the
characteristics compared to the classical
potential.}
}
@ARTICLE{wessner2006anisotropic,
AUTHOR = {Wilfried Wessner AND Johann Cervenka AND Clemens Heitzinger AND Andreas Hössinger AND Siegfried Selberherr},
TITLE = {Anisotropic Mesh Refinement for the Simulation of Three-Dimensional Semiconductor Manufacturing Processes},
JOURNAL = {IEEE Trans. Computer-Aided Design of Integrated Circuits and Systems},
VOLUME = 25,
NUMBER = 10,
PAGES = {2129-2139},
MONTH = OCT,
YEAR = 2006,
DOI = {10.1109/TCAD.2005.862750},
URL = {http://ieeexplore.ieee.org/search/srchabstract.jsp?arnumber=1677696&isnumber=35285&punumber=43&k2dockey=1677696@ieeejrns&query=%28heitzinger+%3Cin%3E+metadata%29+%3Cand%3E+%2843+%3Cin%3E+punumber%29&pos=0},
PDF = {http://ieeexplore.ieee.org/iel5/43/35285/01677696.pdf?tp=&isnumber=35285&arnumber=1677696&punumber=%3Cb%3E%3Cfont%20color=990000%3E43%3C/font%3E%3C/b%3E},
ABSTRACT = {This paper presents an anisotropic adaptation strategy for
three-dimensional unstructured tetrahedral meshes,
which allows us to produce thin mostly anisotropic
layers at the outside margin, i.e., the skin of an
arbitrary meshed simulation domain. An essential
task for any modern algorithm in the finite-element
solution of partial differential equations,
especially in the field of semiconductor process and
device simulation, the major application is to
provide appropriate resolution of the partial
discretization mesh. The start-up conditions for
semiconductor process and device simulations claim
an initial mesh preparation that is performed by
so-called Laplace refinement. The basic idea is to
solve Laplace’s equation on an initial coarse mesh
with Dirichlet boundary conditions. Afterward, the
gradient field is used to form an anisotropic metric
that allows to refine the initial mesh based on
tetrahedral bisection.}
}
@ARTICLE{heitzinger2005method,
AUTHOR = {Clemens Heitzinger AND Alireza Sheikholeslami AND Jong-Mun Park AND Siegfried Selberherr},
TITLE = {A Method for Generating Structurally Aligned Grids for Semiconductor Device Simulation},
JOURNAL = {IEEE Trans. Computer-Aided Design of Integrated Circuits and Systems},
VOLUME = 24,
NUMBER = 10,
PAGES = {1485-1491},
MONTH = OCT,
YEAR = 2005,
URL = {http://ieeexplore.ieee.org/search/srchabstract.jsp?arnumber=1512368&isnumber=32384&punumber=43&k2dockey=1512368@ieeejrns&query=%28heitzinger+%3Cin%3E+metadata%29+%3Cand%3E+%2843+%3Cin%3E+punumber%29&pos=1},
PDF = {http://ieeexplore.ieee.org/iel5/43/32384/01512368.pdf?tp=&isnumber=32384&arnumber=1512368&punumber=%3Cb%3E%3Cfont%20color=990000%3E43%3C/font%3E%3C/b%3E},
ABSTRACT = {The quality of the numeric approximation of the partial
differential equations governing carrier transport
in semiconductor devices depends particularly on the
grid. The method of choice is to use structurally
aligned grids since the regions and directions
therein that determine device behavior are usually
straightforward to find as they depend on the
distribution of doping. Here, the authors present an
algorithm for generating structurally aligned grids
including anisotropy with resolutions varying over
several orders of magnitude. The algorithm is based
on a level set approach and permits to define the
refined resolutions in a flexible manner as a
function of doping. Furthermore, criteria on grid
quality can be enforced. In order to show the
practicability of this method, the authors study the
examples of a trench gate metal-oxide-semiconductor
field-effect transistor (TMOSFET) and a radio
frequency silicon-on-insulator lateral double
diffused metal-oxide-semiconductor (RF SOI LDMOS)
power device using the device simulator MINIMOS NT,
where simulations are performed on a grid generated
by the new algorithm. In order to resolve the
interesting regions of the TMOSFET and the RF SOI
LDMOS power device accurately, several regions of
refinement were defined where the grid was grown
with varying resolutions.}
}
@ARTICLE{vasileska2005quantum,
AUTHOR = {Dragica Vasileska AND Hasanur Khan AND Shaikh Ahmed AND Christian Ringhofer AND Clemens Heitzinger},
TITLE = {Quantum and {Coulomb} Effects in Nanodevices},
JOURNAL = {International Journal of Nanoscience},
VOLUME = 4,
NUMBER = 3,
PAGES = {305-361},
MONTH = JUN,
YEAR = 2005,
URL = {http://www.worldscinet.com/ijn/04/0403/S0219581X05003164.html},
PDF = {http://www.worldscinet.com/ijn/04/preserved-docs/0403/S0219581X05003164.pdf},
ABSTRACT = {In state-of-the-art devices, it is well known that quantum
and Coulomb effects play significant role on the
device operation. In this paper, we demonstrate that
a novel effective potential approach in conjunction
with a Monte Carlo device simulation scheme can
accurately capture the quantum-mechanical size
quantization effects. We also demonstrate, via
proper treatment of the short-range Coulomb
interactions, that there will be significant
variation in device design parameters for devices
fabricated on the same chip due to the presence of
unintentional dopant atoms at random locations
within the channel.}
}
@ARTICLE{ahmed2005quantum,
AUTHOR = {Shaikh Ahmed AND Dragica Vasileska AND Clemens Heitzinger AND Christian Ringhofer},
TITLE = {Quantum Potential Approach to Modeling Nanoscale {MOSFETs}},
JOURNAL = {Journal of Computational Electronics},
VOLUME = 4,
NUMBER = {1-2},
PAGES = {57-61},
YEAR = 2005,
URL = {http://www.springerlink.com/content/q0745k8845157147/?p=3775349bb29e4462a47731b834eecf5b&pi=4},
PDF = {http://www.springerlink.com/content/q0745k8845157147/fulltext.pdf},
ABSTRACT = {We propose a novel parameter-free quantum potential scheme
for use in conjunction with particle-based
simulations. The method is based on a perturbation
theory around thermodynamic equilibrium and leads to
an effective potential scheme in which the size of
the electron depends upon its energy. The approach
has been tested on the example of a MOS-capacitor by
retrieving the correct sheet electron density. It
has also been used in simulations of a 25 nm
n-channel nanoscale MOSFET with high substrate
doping density. We find that the use of the quantum
potential approach gives rise to a threshold voltage
shift of about 220 mV and drain current degradation
of about 30\%.}
}
@ARTICLE{khan2004modeling,
AUTHOR = {Hasanur Khan AND Dragica Vasileska AND Shaikh Ahmed AND Christian Ringhofer AND Clemens Heitzinger},
TITLE = {Modeling of {FinFET}: {3D} {MC} Simulation Using {FMM} and Unintentional Doping Effects on Device Operation},
JOURNAL = {Journal of Computational Electronics},
VOLUME = 3,
NUMBER = {3-4},
PAGES = {337-340},
YEAR = 2004,
URL = {http://www.springerlink.com/content/p187g1k0707k65t4/?p=3775349bb29e4462a47731b834eecf5b&pi=3},
PDF = {http://www.springerlink.com/content/p187g1k0707k65t4/fulltext.pdf},
ABSTRACT = {Novel device concepts such as dual gate SOI, Ultra thin body
SOI, FinFETs, etc., have emerged as a solution to
the ultimate scaling limits of conventional bulk
MOSFETs. These novel devices suppress some of the
Short Channel Effects (SCE) efficiently, but at the
same time more physics based modeling is required to
investigate device operation. In this paper, we use
semi-classical 3D Monte Carlo device simulator to
investigate important issues in the operation of
FinFETs. Fast Multipole Method (FMM) has been
integrated with the EMC scheme to replace the time
consuming Poisson equation solver. Effect of
unintentional doping for different device dimensions
has been investigated. Impurities at the source side
of the channel have most significant impact on the
device performance.}
}
@ARTICLE{holzer2004extraction,
AUTHOR = {Stefan Holzer AND Rainer Minixhofer AND Clemens Heitzinger AND Johannes Fellner AND Tibor Grasser AND Siegfried Selberherr},
TITLE = {Extraction of Material Parameters Based on Inverse Modeling of Three-Dimensional Interconnect Fusing Structures},
JOURNAL = {Microelectronics Journal},
VOLUME = 35,
NUMBER = 10,
PAGES = {805-810},
YEAR = 2004,
URL = {http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V44-4CXTWXT-1&_user=103677&_coverDate=10%2F01%2F2004&_rdoc=5&_fmt=summary&_orig=browse&_srch=doc-info(%23toc%235748%232004%23999649989%23519251%23FLA%23display%23Volume)&_cdi=5748&_sort=d&_docanchor=&view=c&_ct=12&_acct=C000007978&_version=1&_urlVersion=0&_userid=103677&md5=50173218fbb91d7fffc427de2ce77c36},
PDF = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6V44-4CXTWXT-1-K&_cdi=5748&_user=103677&_orig=browse&_coverDate=10%2F01%2F2004&_sk=999649989&view=c&wchp=dGLbVzb-zSkWA&md5=4c8af46a84181bb2cc4443bee0dda4bb&ie=/sdarticle.pdf},
HTML = {http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V44-4CXTWXT-1&_user=103677&_coverDate=10%2F01%2F2004&_rdoc=5&_fmt=full&_orig=browse&_srch=doc-info(%23toc%235748%232004%23999649989%23519251%23FLA%23display%23Volume)&_cdi=5748&_sort=d&_docanchor=&view=c&_ct=12&_acct=C000007978&_version=1&_urlVersion=0&_userid=103677&md5=62e230f1069b06e7f40ebc6a2a9eb884},
ABSTRACT = {An approach for determining higher order coefficients of the
electrical and thermal conductivities for different
materials is presented. The method is based on
inverse modeling using three-dimensional transient
electrothermal finite element simulations for
electrothermal investigations of complex layered
structures, for instance polycrystalline silicon
(polysilicon) fuses or other multi-layered
devices. The simulations are performed with a
three-dimensional interconnect simulator, which is
automatically configured and controlled by an
optimization framework. Our method is intended to be
applied to optimize devices with different material
compositions and geometries as well as for achieving
an optimum of speed and reliability.}
}
@ARTICLE{heitzinger2004feature,
AUTHOR = {Clemens Heitzinger AND Alireza Sheikholeslami AND Fuad Badrieh AND Helmut Puchner AND Siegfried Selberherr},
TITLE = {Feature-Scale Process Simulation and Accurate Capacitance Extraction for the Backend of a 100-nm Aluminum/{TEOS} Process},
JOURNAL = {IEEE Trans. Electron Devices},
VOLUME = 51,
NUMBER = 7,
PAGES = {1129-1134},
MONTH = JUL,
YEAR = 2004,
URL = {http://ieeexplore.ieee.org/search/srchabstract.jsp?arnumber=1308637&isnumber=29042&punumber=16&k2dockey=1308637@ieeejrns&query=%28%28heitzinger%29%3Cin%3Emetadata%29&pos=5},
PDF = {http://ieeexplore.ieee.org/iel5/16/29042/01308637.pdf?tp=&isnumber=29042&arnumber=1308637&punumber=16},
ABSTRACT = {One of the challenges that technology computer-aided design
must meet currently is the analysis of the
performance of groups of components, interconnects,
and, generally speaking, large parts of the IC. This
enables predictions that the simulation of single
components cannot achieve. In this paper, we focus
on the simulation of backend processes, interconnect
capacitances, and time delays. The simulation flows
start from the blank wafer surface and result in
device information for the circuit designer usable
from within SPICE. In order to join topography and
backend simulations, deposition, etching, and
chemical mechanical planarization processes in the
various metal lines are used to build up the backend
stack, starting from the flat wafer
surface. Depending on metal combination,
line-to-line space, and line width, thousands of
simulations are required whose results are stored in
a database. Finally, we present simulation results
for the backend of a 100-nm process, where the
influence of void formation between metal lines
profoundly impacts the performance of the whole
interconnect stack, consisting of aluminum metal
lines, and titanium nitride local
interconnects. Scanning electron microscope images
of test structures are compared to topography
simulations, and very good agreement is
found. Moreover, charge-based capacitance
measurements were carried out to validate the
capacitance extraction, and it was found that the
error is smaller than four percent. These
simulations assist the consistent fabrication of
voids, which is economically advantageous compared
to low-$\kappa$ materials, which suffer from
integration problems.}
}
@ARTICLE{heitzinger2004algorithm,
AUTHOR = {Clemens Heitzinger AND Andreas Hössinger AND Siegfried Selberherr},
TITLE = {An Algorithm for Smoothing Three-Dimensional {Monte Carlo} Ion Implantation Simulation Results},
JOURNAL = {Mathematics and Computers in Simulation},
VOLUME = 66,
NUMBER = {2-3},
PAGES = {219-230},
MONTH = JUN,
YEAR = 2004,
URL = {http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V0T-4BGW348-1&_user=103677&_coverDate=06%2F29%2F2004&_rdoc=10&_fmt=summary&_orig=browse&_srch=doc-info(%23toc%235655%232004%23999339997%23506199%23FLA%23display%23Volume)&_cdi=5655&_sort=d&_docanchor=&view=c&_ct=13&_acct=C000007978&_version=1&_urlVersion=0&_userid=103677&md5=8780e2ecc4ccb01edc1293ee0931056f},
PDF = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6V0T-4BGW348-1-40&_cdi=5655&_user=103677&_orig=browse&_coverDate=06%2F29%2F2004&_sk=999339997&view=c&wchp=dGLbVzW-zSkzV&md5=36c6e1eb5522ca99e2cc94028e626a46&ie=/sdarticle.pdf},
HTML = {http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V0T-4BGW348-1&_user=103677&_coverDate=06%2F29%2F2004&_rdoc=10&_fmt=full&_orig=browse&_srch=doc-info(%23toc%235655%232004%23999339997%23506199%23FLA%23display%23Volume)&_cdi=5655&_sort=d&_docanchor=&view=c&_ct=13&_acct=C000007978&_version=1&_urlVersion=0&_userid=103677&md5=f4e4092bcdf02e85b59685c1aa560a92},
ABSTRACT = {We present an algorithm for smoothing results of
three-dimensional Monte Carlo ion implantation
simulations and translating them from the grid used
for the Monte Carlo simulation to an arbitrary
unstructured three-dimensional grid. This algorithm
is important for joining various simulations of
semiconductor manufacturing process steps, where
data have to be smoothed or transferred from one
grid to another. Furthermore different grids must be
used since using ortho-grids is mandatory because of
performance reasons for certain Monte Carlo
simulation methods. The algorithm is based on
approximations by generalized Bernstein
polynomials. This approach was put on a
mathematically sound basis by proving several
properties of these polynomials. It does not suffer
from the ill effects of least squares fits of
polynomials of fixed degree as known from the
popular response surface method. The smoothing
algorithm which works very fast is described and in
order to show its applicability, the results of
smoothing a three-dimensional real world
implantation example are given and compared with
those of a least squares fit of a multivariate
polynomial of degree 2, which yielded unusable
results.}
}
@ARTICLE{binder2004study,
AUTHOR = {Thomas Binder AND Clemens Heitzinger AND Siegfried Selberherr},
TITLE = {A Study on Global and Local Optimization Techniques for {TCAD} Analysis Tasks},
JOURNAL = {IEEE Trans. Computer-Aided Design of Integrated Circuits and Systems},
VOLUME = 23,
NUMBER = 6,
PAGES = {814-822},
MONTH = JUN,
YEAR = 2004,
URL = {http://ieeexplore.ieee.org/search/srchabstract.jsp?arnumber=1302183&isnumber=28935&punumber=43&k2dockey=1302183@ieeejrns&query=%28heitzinger+%3Cin%3E+metadata%29+%3Cand%3E+%2843+%3Cin%3E+punumber%29&pos=4},
PDF = {http://ieeexplore.ieee.org/iel5/43/28935/01302183.pdf?tp=&isnumber=28935&arnumber=1302183&punumber=%3Cb%3E%3Cfont%20color=990000%3E43%3C/font%3E%3C/b%3E},
ABSTRACT = {We evaluate optimization techniques to reduce the necessary
user interaction for inverse modeling applications
as they are used in the technology computer-aided
design field. Four optimization strategies are
compared. Two well-known global optimization
methods, simulated annealing and genetic
optimization, a local gradient-based optimization
strategy, and a combination of a local and a global
method. We rate the applicability of each method in
terms of the minimal achievable target value for a
given number of simulation runs and in terms of the
fastest convergence. A brief overview over the three
used optimization algorithms is given. The
optimization framework that is used to distribute
the workload over a cluster of workstations is
described. The actual comparison is achieved by
means of an inverse modeling application that is
performed for various settings of the optimization
algorithms. All presented optimization algorithms
are capable of evaluating several targets in
parallel. The best optimization strategy that is
found is used in the calibration of a model for
silicon self-interstitial cluster formation and
dissolution.}
}
@ARTICLE{heitzinger2004note,
AUTHOR = {Clemens Heitzinger AND Christian Ringhofer},
TITLE = {A Note on the Symplectic Integration of the Nonlinear {Schrödinger} Equation},
JOURNAL = {Journal of Computational Electronics},
VOLUME = 3,
NUMBER = 1,
PAGES = {33-44},
YEAR = 2004,
URL = {http://www.springerlink.com/content/h4463821jm220u5t/?p=3775349bb29e4462a47731b834eecf5b&pi=1},
PDF = {http://www.springerlink.com/content/h4463821jm220u5t/fulltext.pdf},
ABSTRACT = {Numerically solving the nonlinear Schrödinger equation and
being able to treat arbitrary space dependent
potentials permits many application in the realm of
quantum mechanics. The long-term stability of a
numerical method and its conservation properties is
an important feature since it assures that the
underlying physics of the solution are respected and
it ensures that the numerical result is correct also
for small time spans. In this paper we describe
symplectic integrators for the nonlinear Schrödinger
equation with arbitrary potentials and perform
numerical experiments comparing different approaches
and highlighting their respective advantages and
disadvantages.}
}
@ARTICLE{heitzinger2004formation,
AUTHOR = {Clemens Heitzinger AND Siegfried Selberherr},
TITLE = {On the Simulation of the Formation and Dissolution of Silicon Self-Interstitial Clusters and the Corresponding Inverse Modeling Problem},
JOURNAL = {Microelectronics Journal},
VOLUME = 35,
NUMBER = 2,
PAGES = {167-171},
MONTH = FEB,
YEAR = 2004,
URL = {http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V44-49XPJ15-1&_user=103677&_coverDate=02%2F29%2F2004&_rdoc=9&_fmt=summary&_orig=browse&_srch=doc-info(%23toc%235748%232004%23999649997%23475108%23FLA%23display%23Volume)&_cdi=5748&_sort=d&_docanchor=&view=c&_ct=16&_acct=C000007978&_version=1&_urlVersion=0&_userid=103677&md5=39083ba6722ea306c8cb62ad73740772},
PDF = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6V44-49XPJ15-1-33&_cdi=5748&_user=103677&_orig=browse&_coverDate=02%2F29%2F2004&_sk=999649997&view=c&wchp=dGLbVzb-zSkzk&md5=3204cfc96191be632aed663d9be92d6d&ie=/sdarticle.pdf},
HTML = {http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V44-49XPJ15-1&_user=103677&_coverDate=02%2F29%2F2004&_rdoc=9&_fmt=full&_orig=browse&_srch=doc-info(%23toc%235748%232004%23999649997%23475108%23FLA%23display%23Volume)&_cdi=5748&_sort=d&_docanchor=&view=c&_ct=16&_acct=C000007978&_version=1&_urlVersion=0&_userid=103677&md5=0a7c1dc34660e04844934633e3ddfb52},
ABSTRACT = {The formation and dissolution of silicon self-interstitial
clusters is linked to the phenomenon of
transient-enhanced diffusion (TED) which in turn has
gained importance in the manufacturing of
semiconductor devices. Based on theoretical
considerations and measurements of the number of
self-interstitial clusters during a thermal step, a
model for the formation and dissolution of
self-interstitial clusters is presented including
the adjusted model parameters for two different
technologies (i.e. material parameter sets). In
order to automate the inverse modeling part, a
general optimization framework was used. In addition
to solving this problem, the same setup can solve a
wide range of inverse modeling problems occurring in
the domain of process simulation. Finally, the
results are discussed and compared with a previous
model.}
}
@ARTICLE{heitzinger2003smoothing,
AUTHOR = {Clemens Heitzinger AND Andreas Hössinger AND Siegfried Selberherr},
TITLE = {On Smoothing Three-Dimensional {Monte Carlo} Ion Implantation Simulation Results},
JOURNAL = {IEEE Trans. Computer-Aided Design of Integrated Circuits and Systems},
VOLUME = 22,
NUMBER = 7,
PAGES = {879-883},
MONTH = JUL,
YEAR = 2003,
URL = {http://ieeexplore.ieee.org/search/srchabstract.jsp?arnumber=1208447&isnumber=27194&punumber=43&k2dockey=1208447@ieeejrns&query=%28heitzinger+%3Cin%3E+metadata%29+%3Cand%3E+%2843+%3Cin%3E+punumber%29&pos=2},
PDF = {http://ieeexplore.ieee.org/iel5/43/27194/01208447.pdf?tp=&isnumber=27194&arnumber=1208447&punumber=%3Cb%3E%3Cfont%20color=990000%3E43%3C/font%3E%3C/b%3E},
ABSTRACT = {An algorithm for smoothing results of three-dimensional
(3-D) Monte Carlo ion implantation simulations and
translating them from the grid used for the Monte
Carlo simulation to an arbitrary unstructured 3-D
grid is presented. This algorithm is important for
joining various process simulation steps, where data
have to be smoothed or transferred from one grid to
another. Furthermore, it is important for
integrating the ion implantation simulator into a
process flow. One reason for using different grids
is that for certain Monte Carlo simulation methods,
using orthogrids is mandatory because of performance
reasons.
The algorithm presented sweeps a small
rectangular grid over the points of the new
tetrahedral grid and uses approximation by
generalized Bernstein polynomials. This approach was
put on a mathematically sound basis by proving
several properties of these polynomials. It does not
suffer from the adverse effects of least squares
fits of polynomials of fixed degree as known from
the response surface method.
The most important
properties of Bernstein polynomials generalized to
cuboid domains are presented, including uniform
convergence, an asymptotic formula, and the
variation diminishing property. The smoothing
algorithm which works very fast is described and, in
order to show its applicability, the resulting
values of a 3-D real world implantation example are
given and compared with those of a least squares fit
of a multivariate polynomial of degree two, which
yielded unusable results.}
}
@ARTICLE{heitzinger2003simulation,
AUTHOR = {Clemens Heitzinger AND Wolfgang Pyka AND Naoki Tamaoki AND Toshiro Takase AND Toshimitsu Ohmine AND Siegfried Selberherr},
TITLE = {Simulation of Arsenic In-Situ Doping with Poly-Silicon {CVD} and its Application to High Aspect Ratio Trenches},
JOURNAL = {IEEE Trans. Computer-Aided Design of Integrated Circuits and Systems},
VOLUME = 22,
NUMBER = 3,
PAGES = {285-292},
MONTH = MAR,
YEAR = 2003,
URL = {http://ieeexplore.ieee.org/search/srchabstract.jsp?arnumber=1182073&isnumber=26533&punumber=43&k2dockey=1182073@ieeejrns&query=%28heitzinger+%3Cin%3E+metadata%29+%3Cand%3E+%2843+%3Cin%3E+punumber%29&pos=3},
PDF = {http://ieeexplore.ieee.org/iel5/43/26533/01182073.pdf?tp=&isnumber=26533&arnumber=1182073&punumber=%3Cb%3E%3Cfont%20color=990000%3E43%3C/font%3E%3C/b%3E},
ABSTRACT = {Filling high aspect ratio trenches is an essential
manufacturing step for state of the art memory
cells. Understanding and simulating the transport
and surface processes enables to achieve voidless
filling of deep trenches, to predict the resulting
profiles, and thus to optimize the process
parameters and the resulting memory cells.
Experiments of arsenic doped polysilicon deposition
show that under certain process conditions step
coverages greater than unity can be achieved. We
developed a new model for the simulation of arsenic
doped polysilicon deposition, which takes into
account surface coverage dependent sticking
coefficients and surface coverage dependent arsenic
incorporation and desorption rates. The additional
introduction of Langmuir--Hinshelwood type time
dependent surface coverage enabled the reproduction
of the bottom up filling of the trenches in
simulations. Additionally, the rigorous treatment of
the time dependent surface coverage allows to trace
the in situ doping of the deposited film.
The model
presented was implemented and simulations were
carried out for different process parameters. Very
good agreement with experimental data was achieved
with theoretically deduced parameters. Simulation
results are shown and discussed for polysilicon
deposition into 0.1$\mu$m wide and 7$\mu$m deep,
high aspect ratio trenches.}
}
@ARTICLE{grasser2002characterization,
AUTHOR = {Tibor Grasser AND Hans Kosina AND Clemens Heitzinger AND Siegfried Selberherr},
TITLE = {Characterization of the Hot Electron Distribution Function Using Six Moments},
JOURNAL = {J. Appl. Phys.},
VOLUME = 91,
NUMBER = 6,
PAGES = {3869-3879},
YEAR = 2002,
URL = {http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JAPIAU000091000006003869000001&idtype=cvips&gifs=yes},
PDF = {http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=JAPIAU000091000006003869000001&idtype=cvips&prog=normal},
HTML = {http://scitation.aip.org/journals/doc/JAPIAU-ft/vol_91/iss_6/3869_1.html},
ABSTRACT = {The shape of the hot electron distribution function in
semiconductor devices is insufficiently described
using only the first four moments. We propose using
six moments of the distribution function to obtain a
more accurate description of hot carrier
phenomena. An analytic expression for the symmetric
part of the distribution function as a function of
the even moments is given which shows good agreement
with Monte Carlo data for both the bulk case and
inside n$^+$-n-n$^+$ test structures. The influence
of the band structure on the parameters of the
distribution function is studied and proven to be of
importance for an accurate description.}
}
@ARTICLE{heitzinger2002extensible,
AUTHOR = {Clemens Heitzinger AND Siegfried Selberherr},
TITLE = {An Extensible {TCAD} Optimization Framework Combining Gradient Based and Genetic Optimizers},
JOURNAL = {Microelectronics Journal (Design, Modeling and Simulation in Microelectronics and {MEMS}; Smart Electronics and {MEMS})},
YEAR = 2002,
VOLUME = 33,
NUMBER = {1-2},
PAGES = {61-68},
URL = {http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V44-44RNMMN-9&_user=103677&_coverDate=01%2F02%2F2002&_rdoc=9&_fmt=summary&_orig=browse&_srch=doc-info(%23toc%235748%232002%23999669998%23279355%23FLA%23display%23Volume)&_cdi=5748&_sort=d&_docanchor=&view=c&_ct=21&_acct=C000007978&_version=1&_urlVersion=0&_userid=103677&md5=c4fe291cc7b11174beac29f24f4f42a3},
PDF = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6V44-44RNMMN-9-10&_cdi=5748&_user=103677&_orig=browse&_coverDate=01%2F02%2F2002&_sk=999669998&view=c&wchp=dGLbVtb-zSkzk&md5=455e6caec00f729b76c54e716bdecf40&ie=/sdarticle.pdf},
HTML = {http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V44-44RNMMN-9&_user=103677&_coverDate=01%2F02%2F2002&_rdoc=9&_fmt=full&_orig=browse&_srch=doc-info(%23toc%235748%232002%23999669998%23279355%23FLA%23display%23Volume)&_cdi=5748&_sort=d&_docanchor=&view=c&_ct=21&_acct=C000007978&_version=1&_urlVersion=0&_userid=103677&md5=4d1c918839690f0c4321db0eff56a409},
ABSTRACT = {The SIESTA framework is an extensible tool for optimization
and inverse modeling of semiconductor devices
including dynamic load balancing for taking
advantage of several, loosely connected
workstations. Two gradient-based and two
evolutionary computation optimizers are currently
available through a uniform interface and can be
combined at will. At a real world inverse modeling
example, we demonstrate that evolutionary
computation optimizers provide several advantages
over gradient-based optimizers, due to the specific
properties of the objective functions in TCAD
applications. Furthermore, we shortly discuss some
issues arising in inverse modeling and conclude with
a comparison of gradient-based and evolutionary
computation optimizers from a TCAD point of view.}
}
@ARTICLE{grasser2002accurate,
AUTHOR = {Tibor Grasser AND Hans Kosina AND Clemens Heitzinger AND Siegfried Selberherr},
TITLE = {An Accurate Impact Ionization Model which Accounts for Hot and Cold Carrier Populations},
JOURNAL = {Appl. Phys. Lett.},
VOLUME = 80,
NUMBER = 4,
MONTH = JAN,
PAGES = {613-615},
YEAR = 2002,
URL = {http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=APPLAB000080000004000613000001&idtype=cvips&gifs=yes},
PDF = {http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=APPLAB000080000004000613000001&idtype=cvips&prog=normal},
HTML = {http://scitation.aip.org/journals/doc/APPLAB-ft/vol_80/iss_4/613_1.html},
ABSTRACT = {Conventional macroscopic impact ionization models which use
the average carrier energy as a main parameter can
not accurately describe the phenomenon in modern
miniaturized devices. Here, we present a model which
is based on an analytic expression for the
distribution function. In particular, the
distribution function model accounts explicitly for
a hot and a cold carrier population in the drain
region of metal-oxide-semiconductor
transistors. The parameters are determined by
three-even moments obtained from a solution of a
six-moments transport model. Together with a
nonparabolic description of the density of states,
accurate closed form macroscopic impact ionization
models can be derived based on familiar microscopic
descriptions.}
}
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