bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Theory for Testability‐Preserving Optimization ofCombinational Circuits
Authors: Zhu Jiabi , Abd-El-Barr Mostafa , McCrosky Carl
Published: September 2007

Testability should be considered as early as possible in VLSI synthesis and optimization. In
most CAD tools, testability preservation is achieved as a by‐product of finding a less redundant
implementation. Unfortunately, this approach is not supported by theory. It is essential
to have an optimization scheme that systematically preserves testability. A complete theory
covering testability‐preserving optimization of combinational circuits is yet to be developed.

In this paper, a new testability‐preserving theory is established. This theory covers most
optimization cases in the synthesis of irredundant circuits. Optimization of redundant circuits
is also considered. Algorithms based on this theory are proposed. Experiments to verify the
theory and algorithms are reported. The developed theory and algorithms are more general
than previous results.
Greedy Segmented Channel Router
Authors: Bhatia Dinesh , Shankar V.
Published: September 2007

An efficient solution to the generalized detailed routing problem in segmented channels for
row‐based FPGAs is presented. A generalized detailed routing allows routing of each connection
using an arbitrary number of tracks, i.e., doglegs are allowed. This approach is
different from the normally followed method where each connection is routed on a single
straight track. We present a router that performs generalized segmented channel routing
using a greedy approach to route channels. The router also renders itself to limited tolerance
against faults in the routing architecture.
A Fast Clustering‐Based Min‐Cut Placement AlgorithmWith Simulated‐Annealing Performance
Authors: Saab Youssef
Published: September 2007

Placement is an important constrained optimization problem in the design of very large scale
(VLSI) integrated circuits [1–4]. Simulated annealing [5] and min‐cut placement [6] are two
of the most successful approaches to the placement problem. Min‐cut methods yield less
congested and more routable placements at the expense of more wire‐length, while simulated
annealing methods tend to optimize more the total wire‐length with little emphasis on the
minimization of congestion. It is also well known that min‐cut algorithms are substantially
faster than simulated‐annealing‐based methods. In this paper, a fast min‐cut algorithm
(ROW‐PLACE) for row‐based placement is presented and is empirically shown to achieve
simulated‐annealing‐quality wire‐length on a number of benchmark circuits. In comparison
with Timberwolf 6 [7], ROW‐PLACE is at least 12 times faster in its normal mode and is at
least 25 times faster in its faster mode. The good results of ROW‐PLACE are achieved using
a very effective clustering‐based partitioning algorithm in combination with constructive
methods that reduce the wire‐length of nets involved in terminal propagation.
A Hardware Accelerator for Fault Simulation Utilizing a Reconfigurable Array Architecture
Authors: Kang Sungho , Hur Youngmin , Szygenda Stephen A.
Published: September 2007

In order to reduce cost and to achieve high speed a new hardware accelerator for fault simulation has been designed. The architecture of the new accelerator is based on a reconfigurabl mesh type processing element (PE) array. Circuit elements at the same topological level are simulated concurrently, as in a pipelined process. A new parallel simulation algorithm expands all of the gates to two input gates in order to limit the number of faults to two at each gate, so that the faults can be distributed uniformly throughout the PE array. The PE array reconfiguration operation provides a simulation speed advantage by maximizing the use of each PE cell.

This new approach provides for a high performance, cost effective, gain over software simulation. Simulation results show that the hardware accelerator is orders of magnitude faster than the software simulation program.
An Efficient and Fast Algorithm for RoutingOver the Cells
Authors: Chang Kuo-En , Chen Sei-Wang
Published: September 2007

A linear time algorithm for routing over the cells is presented. The algorithm tries to reduce
maximum channel density by routing some connections over the cells. The algorithm first
defines a new scheme for channel representation and formulates the problem based on an
intersection graph derived from the new scheme. Then, a feasible independent set of the
intersection graph is found for routing some subnets over the cells. The algorithm is implemented
and evaluated with several well known benchmarks. In comparison with previous
research, our results are satisfactory, and the algorithm takes substantially less CPU time
than those of previous works. For Deutsch′s difficult example, the previous algorithms take
about 29.25 seconds on an average but our new algorithm needs only 5.6 seconds.
Layout Modeling and Design Space Exploration in Pss1 System
Authors: Tsai Fur-Shing , Hsu Yu-Chin
Published: September 2007

This paper presents the design methodology used in PSS1, a high level synthesis system
designed for computation dominated applications. It includes a behavior synthesizer and an
area optimizer. Based on a pre‐defined architecture, the behavior synthesizer translates a
description into a number of designs with different delays and hardware costs. Based on a
two‐level layout model, the area optimizer fine‐tunes the physical design using the information
feedback from the layout tools. All the tools are linked by an X‐window interface in
which users can traverse among different tools and interactively change the design parameters.
The output is linked to Lager system [7], a silicon assembler. The layout model allows
a designer to interactively merge/split modules, change the shape of modules, and define the
pin positions of modules. Experiments show that a considerable area improvement has been
achieved using this methodology.
Current Testing of CMOS Combinational Circuits withSingle Floating Gate Defects
Authors: Champac Victor H. , Figueras Joan
Published: September 2007

The behavior of basic CMOS combinational gates in the presence of a floating gate defect is
characterized in order to investigate its detectability by IDDQ
. The defect is modeled at the
circuit level by the poly‐bulk and metal‐poly capacitances, which determine the quiescent
power supply current consumption (IDDQ
) of the defective circuit. The testing implications
on the type of defective gate are studied. Experimental measures have been made on basic
CMOS combinational modules designed with intentional floating gate defects. A good agreement
is observed between the simulation results and the experimental data. A conventional
ATPG for stuck‐at faults is used to obtain the required exciting vector to test the floating gate
defects by IDDQ
Testing.
Numerical Examination of Photon Recycling as anExplanation of Observed Carrier Lifetime in DirectBandgap Materials
Authors: Parks Joseph W. , Brennan Kevin F. , Smith Arlynn W.
Published: September 2007

Photon recycling is examined as an explanation for the observed large carrier lifetimes in
an InP/InGaAs photodiode. This effect extends the effective carrier lifetime within a
device by re‐absorbing a fraction of the photons generated through radiative band‐toband
recombination events. In order to predict the behavior of this carrier generation,
photon recycling has been added to our two‐dimensional macroscopic device simulator,
STEBS‐2D. A ray‐tracing preprocessing step is used to map all of the possible
trajectories and absorption of various wavelengths of emitted light from each
originating node within the device. The macroscopic simulator uses these data to
determine the spatial location of the re‐absorbed radiation within the geometry of the
device. By incorporating the ray tracer results with the total quantity and spectral
content of recombined carriers at each node within the simulation, the recycled
generation rate can be obtained. A practical application of this model is presented where
the effects of photon recycling are used as a possible explanation of the discrepancy
between the theoretically predicted and experimentally observed radiative recombination
rate in a double heterostructure photodetector.
lntersubband Relaxation in Step QuantumWell Structures
Authors: Sun J. P. , Teng H. B. , Haddad G. I. , Stroscio M. A. , Iafrate G. J.
Published: September 2007

Intersubband relaxation due to electron interactions with the localized phonon modes
plays an important role for population inversion in quantum well laser structures
designed for intersubband lasers operating at mid‐infrared to submillimeter wavelengths.
In this work, intersubband relaxation rates between subbands in step quantum
well structures are evaluated numerically using Fermi′s golden rule, in which the
localized phonon modes including the asymmetric interface modes, symmetric interface
modes, and confined phonon modes and the electron – phonon interaction Hamiltonians
are derived based on the macroscopic dielectric continuum model, whereas the
electron wave functions are obtained by solving the Schrödinger equation for the
heterostructures under investigation. The sum rule for the relationship between the form
factors of the various localized phonon modes and the bulk phonon modes is examined
and verified for these structures. The intersubband relaxation rates due to electron
scattering by the asymmetric interface phonons, symmetric interface phonons, and
confined phonons are calculated and compared with the relaxation rates calculated
using the bulk phonon modes and the Fröhlich interaction Hamiltonian for step
quantum well structures with subband separations of 36 meV and 50meV, corresponding
to the bulk longitudinal optical phonon energy and interface phonon energy,
respectively. Our results show that for preferential electron relaxation in intersubband
laser structures, the effects of the localized phonon modes, especially the interface
phonon modes, must be included for optimal design of these structures.
Plasma Process Modeling for Integrated CircuitsManufacturing
Authors: Meyyappan M. , Govindan T. R.
Published: September 2007

A reactor model for plasma‐based deposition and etching is presented. Two‐dimensional
results are discussed in terms of plasma density, ion flux, and ion energy. Approaches to
develop rapid CAD‐type models are discussed.
Hydrodynamic Device Modeling with Band Nonparabolicity
Authors: Cai J. , Cui H. L. , Lenzing E. H. , Pastore R. , Rhodes D. L. , Perlman B. S.
Published: September 2007

A semiconductor device model based on a set of quantum mechanically derived hydrodynamic
balance equations are presented. This model takes full account of band nonparabolicity,
in addition to its other useful features such as the explicit evaluation of momentum and
energy relaxation rates, in the form of frictional force and energy loss rate, within the model,
and inclusion of carrier‐carrier interaction effects, such as dynamical screening. Numerical
results of one‐dimensional device simulations are presented and compared with parabolic
approximations.
A New HEMT Breakdown Model IncorporatingGate and Thermal Effects
Authors: Albasha Lutfi , Snowden Christopher M. , Pollard Roger D.
Published: September 2007

This paper presents a comprehensive physical model for the breakdown process in
HEMTs. The model is integrated into in a fast quasi‐two‐dimensional HEMT physical
simulator. The work is based on a full study of the complex interactions between the
different breakdown mechanisms and the influence of design parameters. The model
takes account of tunnelling effects in the region of the gate metallization, and of the
thermal effects in the active channel under the gate region.
Placement and Routing for Performance‐Oriented FPGA Layout
Authors: Alexander Michael J. , Cohoon James P. , Ganley Joseph L. , Robins Gabriel
Published: September 2007

This paper presents a performance‐oriented placement and routing tool for field‐programmable
gate arrays. Using recursive geometric partitioning for simultaneous
placement and global routing, and a graph‐based strategy for detailed routing, our tool
optimizes source‐sink pathlengths, channel width and total wirelength. Our results
compare favorably with other FPGA layout tools, as measured by the maximum
channel width required to place and route several benchmarks.
SPIN – A Schrödinger‐Poisson Solver IncludingNonparabolic Bands
Authors: Kosina H. , Troger C.
Published: September 2007

Nonparabolicity effects in two‐dimensional electron systems are quantitatively
analyzed. A formalism has been developed which allows to incorporate a nonparabolic
bulk dispersion relation into the Schrödinger equation. As a consequence of
nonparabolicity the wave functions depend on the in‐plane momentum. Each subband
is parametrized by its energy, effective mass and a subband nonparabolicity coefficient.
The formalism is implemented in a one‐dimensional Schrödinger‐Poisson solver which
is applicable both to silicon inversion layers and heterostructures.
Moment Closure Hierarchies for the Boltzmann‐Poisson Equation
Authors: Levermore C. David
Published: September 2007

We outline a systematic nonperturbative derivation of a hierarchy of closed systems of
moment equations that can be applied to any kinetic description of electrons in a semiconductor.
This entropy based closure procedure extends one that was introduced in the context of
gas dynamics. In the context of semiconductors, this procedure yields generalizations of socalled
hydrodynamic models. It is illustrated on the semiclassical Boltzmann‐Poisson equation
for a single conduction band in the parabolic band approximation.
Temperature Dependence of the Electron and HoleScattering Mechanisms in Silicon Analyzed through aFull‐Band, Spherical‐Harmonics Solution of the BTE
Authors: Reggiani Susanna , Vecchi Maria Cristina , Rudan Massimo
Published: September 2007

By adopting the solution method for the BTE based on the spherical‐harmonics
expansion (SHE) [1], and using the full‐band structure for both the electron and valence
band of silicon [2], the temperature dependence of a number of scattering mechanisms
has been modeled and implemented into the code HARM performing the SHE solution.
Comparisons with the experimental mobility data show agreement over a wide range of
temperatures. The analysis points out a number of factors from which the difficulties
encountered in earlier investigations seemingly originate, particularly in the case of hole
mobility.
A New Method to Recover Vectorial Electric Fields andCurrent Densities from Unstructured Meshes
Authors: Kerr Daniel C. , Mayergoyz Isaak D.
Published: September 2007

In the context of 2‐D and 3‐D unstructured mixed‐element meshes, a new method of recovering
vectorial fields and currents in multidimensional simulation is introduced. The new
method, called the method of edge elements, directly interpolates the projections of the vectors
on the edges of an element into its interior. The new method is compared to two other
recovery methods on the basis of resolution, consistency, and implementation ease.
Quadrilateral Finite Element Monte Carlo Simulation of Complex Shape Compound FETs
Authors: Babiker S. , Asenov A. , Barker J. R. , Beaumont S. P.
Published: September 2007

The complex recess and gate shape of modem compound FETs greatly affect the device parasitics
and therefore impose the need for proper description of the device geometry and surface
conditions in any practical device simulations. In this paper we describe a new Monte Carlo
(MC) module incorporated in our Heterojunction 2D Finite element FET simulator H2F [1].
The module combines realistic quadrilateral finite‐element description of the device geometry
with realistic particle simulation of the non‐equilibrium hot carrier transport in short
recess gate compound FETs. A Single Programme Multiple Data (SPMD) parallel approach
makes it possible to use our MC simulator for practical design work, generating the necessary
I‐V characteristics in parallel. The capabilities of the finite element MC module are illustrated
in example simulations of a 200nm pseudomorphic HEMT fabricated in the Nanoelectronics
Research Centre of Glasgow University.
Simulation of a Single Electron Tunnel Transistor with Inclusion of Inelastic Macroscopic QuantumTunneling of Charge
Authors: Wasshuber Christoph , Kosina Hans
Published: September 2007

We simulated a Single Electron Tunnel (SET) Transistor with the full inclusion of inelastic
macroscopic quantum tunneling of charge (q‐MQT) or co‐tunneling. Numerical results of the
q‐MQT effect over a wide range of bias and gate voltage were achieved.

Monte Carlo method was used to simulate electrons that tunnel back and forth through
the two tunnel junctions of the SET transistor and co‐tunnel back and forth through both junctions
simultaneously.

Resonances in the I‐V characteristic were found. The resonant peaks decrease with
increasing temperature. The origin of this resonance is the q‐MQT or co‐tunnel effect in contrast
with the normal resonant tunneling in double barriers.
A New Self‐Consistent 2D Device Simulator Based onDeterministic Solution of the Boltzmann, Poisson andHole‐Continuity Equations
Authors: Liang Wenchao , Goldsman Neil , Mayergoyz Isaak
Published: September 2007

LDD MOSFET simulation is performed by directly solving the Boltzmann Transport Equation
for electrons, the Hole‐Current Continuity Equation and the Poisson Equation self‐consistently.
The spherical harmonic expansion method is employed along with a new
Scharfetter‐Gummel like discretization of the Boltzmann equation. The solution efficiently
provides the distribution function, electrostatic potential, and the hole concentration for the
entire 2‐D MOSFET.
Electronic Structure Calculations UsingAn Adaptive Wavelet Basis
Authors: Richie D. A. , von Allmen P. , Hess K. , Martin Richard M.
Published: September 2007

The use of a wavelet basis can lead to efficient methods for performing ab initio
electronic structure calculations of inherently localized structures. In this work wavelets
are used to construct an adaptive basis which is optimized dynamically throughout the
calculation. The computational effort of such a method should scale linearly with the
number of basis functions. The adaptive basis is tested for the case of bulk Si using only
a local s‐pseudopotential.
Theory of Electron Transport in Small SemiconductorDevices Using the Pauli Master Equation
Authors: Fischetti M. V.
Published: September 2007

It is argued that the Pauli master equation can be used to simulate electron transport in
very small electronic devices under steady‐state conditions. Written in a basis of suitable
wavefunctions and with the appropriate open boundary conditions, this equation
removes some of the approximations which render the Boltzmann equation
unsatisfactory at small length‐scales. The main problems consist in describing the
interaction of the system with the reservoirs and in assessing the range of validity of the
equation: Only devices smaller than the size of the electron wavepackets injected from
the contacts can be handled. Two one‐dimensional examples solved by a simple Monte
Carlo technique are presented.
Ab‐initio Coulomb Scattering in AtomisticDevice Simulation
Authors: Arokianathan C. R. , Davies J. H. , Asenov A.
Published: September 2007

As devices shrink to dimensions below 0.1 μm, it becomes essential to treat impurities
and carriers as individual charges. We describe some approaches to ionised impurity
scattering where the potential of the impurities is included directly in the dynamics of a
Monto Carlo type simulation rather than as a scattering rate. The divergence in the
Coulomb potential creates difficulties for mesh‐based solutions of Poisson′s equation,
which we have compared with more accurate Ewald summation. However, we find that
the mesh does not introduce significant errors, and reproduces well the expected
mobility as a function of doping. Highly accurate integration of the equation of motion
is needed for free carriers, and the initial distribution is problematic. In contrast, a
simple treatment of phonon scattering by Brownian dynamics is more tolerant of errors
because it tends to restore the system to equilibrium.
Self‐Consistent Calculations of the Ground Stateand the Capacitance of a 3D Si/SiO2 Quantum Dot
Authors: Scholze A. , Wettstein A. , Schenk A. , Fichtner W.
Published: September 2007

We perform self‐consistent electronic structure calculations in the framework of
inhomogeneously and anisotropically scaled local density functional theory of a fully
3D modeled Si/SiO2 quantum dot. Electrons are laterally confined in the semiconductor/
oxide heterojunction by a metallic gate atop of the device. Total charge densities,
total free energies, chemical potentials for different numbers of electrons in the dot, and
the differential capacitances for various dot sizes are calculated. We observe shell filling
effects in the differential capacitance. The magic‐numbers are governed by the six valley
bandstructure of silicon, which leads to four fold degenerated single particle levels in the
dot.
Cellular Automata Studies of Vertical Silicon Devices
Authors: Saraniti M. , Zandler G. , Formicone G. , Goodnick S.
Published: September 2007

We present systematic theoretical Cellular Automata (CA) studies of a novel nanometer
scale Si device, namely vertically grown Metal Oxide Field Effect Transistors
(MOSFET) with channel lengths between 65 and 120 nm. The CA simulations predict
drain characteristics and output conductance as a function of gate length. The excellent
agreement with available experimental data indicates a high quality oxide/semiconductor
interface. Impact ionization is shown to be of minor importance. For
inhomogeneous p‐doping profiles along the channel, significantly improved drain
current saturation is predicted.
Multilevel Algorithms for Large‐scope Molecular DynamicsSimulations of Nanostructures on Parallel Computers
Authors: Nakano Aiichiro , Kalia Rajiv K. , Vashishta Priya
Published: September 2007

Molecular Dynamics (MD) is a powerful tool for the atomistic understanding of longrange
stress‐mediated phenomena, phonon properties, and mechanical failure of
nanostructures. For realistic modeling of nanostructures, however, the scope of
simulations must be extended to large system sizes, long simulated times, and complex
realism. We have developed new multilevel algorithms and physical models encompassing
multiple levels of abstraction: i) space‐time multiresolution schemes; ii) adaptive
curvilinear‐coordinate load balancing; iii) hierarchical dynamics via a rigid‐body/
implicit‐integration/normal‐mode approach; iv) variable‐charge MD based on electronegativity
equalization; and v) multilevel preconditioned conjugate gradient method.
Fuzzy clustering is used to facilitate the seamless integration of the multiple levels of
abstraction.
Simulation of Optical Excitation to and Emissionfrom Electron Fabry‐Perot States Subject to StrongInelastic Scattering.
Authors: Register Leonard F.
Published: September 2007

Photon induced carrier excitation to and escape from Fabry‐Perot electron states in the presence
of subsequent inelastic scattering is simulated. The Fabry‐Perot states exist above a
quantum well sandwiched between quarter‐wave stacks of potential wells and barriers. Two
numerical methods are used: simulation of inelastic scattering via absorbing (optical) potentials,
and simulation via Schrödinger Equation Monte Carlo.
Ensemble Monte Carlo and Full‐Wave ElectrodynamicModels Implemented Self‐Consistently on a ParallelProcessor Using Perfectly Matched LayerBoundary Conditions
Authors: Lim Ik-Sung , Grondin Robert O. , El-Ghazaly Samir
Published: September 2007

We have been using a self‐consistent formulation of full‐wave electromagnetic solvers and
ensemble Monte Carlo techniques to model ultrafast photoconductivity. Our simulations
are running on a MasPar machine. This paper will address aspects ofthis simulation which
may interest workers who are simulating not only photoconductive systems but other
systems as well which involve electrodynamics, waves and wave phenomena and ensemble
Monte Carlo transport models. In particular, we will report on the inclusion of perfectly
matched layer approaches to absorbing boundary conditions for electromagnetic waves.
These have in the past several years become widely used in computational electromagnetics
codes because they reduce error due to spurious numerical wave reflection off of
an absorbing boundary by several orders of magnitude. We will also address the issue of
computational cost and show that a full‐wave electromagnetic approach is more
competitive with a Poisson′s equation approach than one might believe. Lastly, our
system has the feature that the active portion where the electrons and holes lie is in fact a
small fraction of the total experimental system′s volume. Unless care is exerted one either
has a very significant load imbalance problem or high communications overhead. We
compare two different tradeoffs between load imbalance and communications overhead.
Monte Carlo and hydrodynamic simulationof a one dimensional n+ ‐ n ‐ n+ silicon diode
Authors: Muscato O. , Pidatella R. M. , Fischetti M. V.
Published: September 2007

An improved closure relation ‐ based on the entropy principle ‐ is implemented in a Hydrodynamic
model for electron transport. Steady‐state electron transport in the “benchmark” n+ ‐ n ‐ n+ submicron silicon diode is simulated and the quality of the model is assessed by comparison
with Monte Carlo results.
On Hartree–Fock Systems
Authors: Gasser I.
Published: September 2007

We show an existence and uniqueness result for mildly nonlinear Schrödinger systems of
(self‐consistent) Hartree–Fock form. We also shortly resume the already existing results
on the semiclassical limit and the asymptotic and dispersive behavior of such systems.
An Efficient Algorithm for the Calculationof Generalized Adding and Arithmetic TransformsFrom Disjoint Cubes of Boolean Functions
Authors: Falkowski Bogdan J. , Chang Chip-Hong
Published: September 2007

A new algorithm is given that converts a reduced representation of Boolean functions in
the form of disjoint cubes to Generalized Adding and Arithmetic spectra. Since the
known algorithms that generate Adding and Arithmetic spectra always start from the
truth table of Boolean functions the method presented computes faster with a smaller
computer memory. The method is extremely efficient for such Boolean functions that
are described by only few disjoint cubes and it allows the calculation of only selected
spectral coefficients, or all the coefficients can be calculated in parallel.
A Fast Algorithm for Performance‐Driven Module Implementation Selection
Authors: Cheng Edward Y. C. , Sahni Sartaj
Published: September 2007

We develop an O(p log n) time algorithm to obtain optimal solutions to the p‐pin n‐net
single channel performance‐driven implementation selection problem in which each
module has at most two possible implementations (2‐PDMIS). Although Her, Wang
and Wong [1] have also developed an O(p log n) algorithm for this problem, experiments
indicate that our algorithm is twice as fast on small circuits and up to eleven times
as fast on larger circuits. We also develop an O(pnc−1) time algorithm for the c, c > 1,
channel version of the 2‐PDMIS problem.
Accurate Interconnection Length Estimations for Predictions Early in the Design Cycle
Authors: Stroobandt Dirk , Campenhout Jan Van
Published: September 2007

Important layout properties of electronic circuits include space requirements and
interconnection lengths. In the process of designing these circuits, a reliable pre‐layout
interconnection length estimation is essential for improving placement and routing
techniques. Donath found an upper bound for the average interconnection length that
follows the trends of experimentally observed average lengths. Yet, this upper bound
deviates from the experimental value by a factor δ  ≈  2, which is not sufficiently accurate
for some applications. We show that we obtain a significantly more accurate estimate by
taking into account the inherent features of the optimal placement process.
Optimal Differential Routing based on Finite StateMachine Theory
Authors: Krishnamoorthy M. S. , Loy James R. , McDonald John F.
Published: September 2007

Noise margins in high speed digital systems continue to erode. Full differential signal
routing provides a mechanism for deferring these effects. This paper proposes a three
stage routing process for solving the adjacent placement routing problem of differential
signal pairs, and proves that it is optimal. The process views differential pairs as logical
nets; routes the logical nets; then bifurcates the result to achieve a physical realization.
Finite state machine theory provides the critical theoretical underpinning and formal
proof of correctness necessary for linear time bifurcation. Regular expressions map the
theoretical solution to an appropriate implementation strategy that employs feature
vectors for net recognition.
A Practical Load‐optimized VCO Design for Low‐jitter 5V 500 MHz Digital Phase‐locked Loop
Authors: Wang Chua-Chin , Chien Yu-Tsun , Chen Ying-Pei
Published: September 2007

In high‐speed digital systems and high‐resolution display devices, the jitter effect of
phase‐locked loops (PLL) limits the system performance. Power supply noise coupling is
one of the major causes of PLL jitter problems, especially with mixed‐signal systems.
The paper presents a targeted 5.0V 500 MHz PLL which is implemented by a 0.6 um
1P3M digital CMOS technology. The features of the proposed design include a load‐optimized
3‐stage VCO, a frequency limiter RC circuit, and a ratioed VCO controlling
current mirror. The jitter, thus, is reduced to 72.693 ps at 600 MHz at the presence of
supply noise, while the sensitivity is limited to 286.6 ps/V. This high‐noise immunity
design allows that the PLL can be integrated with digital circuits.
Design and Analysis of Digital Ratioed Compressors for Inner Product Processing
Authors: Wang Chua-Chin , Huang Chenn-Jung , Lee Po-Ming
Published: September 2007

Inner product calculations are often required in digital neural computing. The critical
path of the inner product of two binary vectors is the carry propagation delay generated
from individual product terms. In this work, two architectures to arrange digital ratioed
compressors are presented to reduce the carry propagation delay in the critical path.
Besides, the carry propagation delay estimation of these compressor building blocks is
derived and compared. The theoretical analysis and Verilog simulation both indicate
that one of the compressor building blocks we present here might offer a sub‐optimal
solution for the basic building blocks used in digital hardware realization of the inner
product computation.
A Modular and Scalable Architecture for the Realization of High‐speed Programmable Rank Order Filters Using Threshold Logic
Authors: Hatirnaz İ. , Gürkaynak F. K. , Leblebici Y.
Published: September 2007

We present a new scalable architecture for the realization of fully programmable rank
order filters (ROF). Capacitive Threshold Logic (CTL) gates are utilized for the
implementation of the multi‐input programmable majority (voting) functions required
in the architecture. The CTL‐based realization of the majority gates used in the ROF
architecture allows the filter rank as well as the window size to be user‐programmable,
using a much smaller silicon area, compared to conventional realizations of digital
median filters. The proposed filter architecture is completely modular and scalable, and
the circuit complexity grows only linearly with maximum window size (m) and with
word length (n). A prototype of the proposed filter circuit has been designed and
fabricated using double‐polysilicon 0.8 μm CMOS technology. Detailed post‐layout
simulations and test results of the ROF prototype circuit indicate that the new
architecture can accommodate sampling clock rates of up to 50 MHz, corresponding to
an effective data processing rate of 800 Mb/s for a very large filter with window size 63
and word length of 16 bits.
Operation Principle of Resonant TunnelingTHz Oscillator at Fixed Bias Voltages
Authors: Zhao Peiji , Cui H. L. , Woolard D. , Buot Fliex
Published: September 2007

Based on time‐dependent numerical simulation of an double barrier quantum well
structure, a time‐dependent energy coupling model is presented to account for the
operational principle of a new kind of resonant tunneling THz oscillators.
Three‐dimensional Statistical Modeling of the Effectsof the Random Distribution of Dopantsin Deep Sub‐micron nMOSFETs
Authors: Amirante E. , Iannaccone G. , Pellegrini B.
Published: September 2007

We have performed a three‐dimensional statistical simulation of the threshold voltage
distribution of deep submicron nMOSFETs, as a function of gate length, doping
density, oxide thickness, based on a multigrid non‐linear Poisson solver. We compare
our results with statistical simulations presented in the literature, and show that
essentially only the vertical distribution of dopants has an effect on the standard
deviation of the threshold voltage.
Electronic Transport in Self‐organised MolecularNanostructured Devices
Authors: Pecchia A. , Movaghar B. , Kelsall R. W. , Bourlange A. , Evans S. D. , Hickey B. J. , Boden N.
Published: September 2007

We analyse the frequency dependent conductivity of a system which is fabricated using
the combination of a quasi 2‐dimensional MBE grown metal film and an ordered self‐assembled
overlayer of adsorbed molecules. The molecules can self‐assemble to form
quasi 1‐dimensional conducting columns, in which electrons can be temporarily
trapped. Given the short mean free path of conducting electrons, due to surface and
impurity scattering, the long range transport is modelled using a diffusion scheme
through a discrete lattice, whose sites are defined by the locations of the self‐organised
molecular columns. Local conductivities are computed using the Kubo formalism and
mapped into effective transfer rates between adjacent sites of the lattice. This model
includes stochastic excursions of electrons into the molecular states, as well as the
quantum mechanical details of short range transport. External nano‐engineered gate
fields can be used to control the residence time of carriers in molecular bands.
Calculations demonstrate that the in‐plane conductivity is decreased at low frequency
due to electron capture in the molecular columns, and that this effect becomes stronger
as the length of the columns is increased.
Power‐conscious Scheduling for Real‐time Embedded Systems Design
Authors: Shin Youngsoo , Choi Kiyoung , Sakurai Takayasu
Published: September 2007

Power efficient design of real‐time embedded systems based on programmable processors
becomes more important as system functionality is increasingly realized through
software. We address a power optimization method for real‐time embedded applications
on a variable speed processor. The method combines off‐line and on‐line components.
The off‐line component determines the lowest possible maximum processor speed while
guaranteeing deadlines of all tasks. The on‐line component dynamically varies the processor
speed or bring a processor into a power‐down mode to exploit execution time
variations and idle intervals. Experimental results show that the proposed method
obtains a significant power reduction across several kinds of applications.
Simulation of 0.35 μm/0.25 μm CMOSTechnology Doping Profiles
Authors: Lorenzini M. , Haspeslagh L. , Van Houdt J. , Maes H. E.
Published: September 2007

A careful calibration of a continuum process simulator is normally required to achieve a
good agreement between simulated results and experimental dopant profiles. However,
the validity of such a calibration procedure is often limited to a particular technology.
By taking into account a number of physics‐based models and experimental results
available in literature, the predicting capability of the process simulation has been
conveniently improved. In particular, this paper shows how concentration‐depth
profiles from two different CMOS technologies have been successfully reproduced with
a unique set of fitting parameters.
A Fast and Accurate Method of Power Estimation for Logic Level Networks
Authors: Theodoridis G. , Theoharis S. , Soudris D. , Goutis C.
Published: September 2007

A method for estimating the power consumption of multilevel combinational networks
is introduced. The proposed method has as inputs the signal probabilities, the data
correlations of the primary inputs and the structure of the circuit, and consists of two
major steps: (i) the calculation of the switching activity on an individual gate and (ii) the
calculation of the switching activity of any node of the network. The foregoing step
includes the derivation of novel formulas for calculating the switching activity of basic
gates. The latter step includes the development of an algorithm, which propagates the
signal probabilities through the network and calculates the switching activity of any
logic node. The proposed method provides accurate switching activity values
performing their calculation in reduced time interval. The experimental results prove
that the proposed method achieves significant reduction up to 50% in terms of
multiplications compared to method of [6].
Dynamical Equation and Monte Carlo Simulationof the Two‐time Wigner Function for ElectronQuantum Transport
Authors: Brunetti R. , Bertoni A. , Bordone P. , Jacoboni C.
Published: September 2007

Within the Wigner‐function formalism for electron quantum transport in semiconductors
a two‐time Wigner function is defined starting from the Green‐function formalism.
After a proper Fourier transform a Wigner function depending on p and w as
independent variables is obtained. This new Wigner function extends the Wigner
formalism to the frequency domain and carries information related to the spectral
density of the system. A Monte Carlo approach based on the generation of Wigner
paths, already developed for the single‐time Wigner function, has been extended to
evaluate the momentum and energy‐dependent Wigner function. Results will be shown
for electrons subject to the action of an external field and in presence of scattering with
optical phonons.
Evaluation of an Equivalent Hole Effective Massfor Si/SiGe Structures
Authors: Rodríguez Salvador , Banqueri J. , Carceller J. E.
Published: September 2007

We have studied the carrier profile and calculated a unique effective mass for a two‐dimensional
hole gas confined in a SiO2/Si/Si1_xGex/Si structure when an external
voltage is applied. For this purpose, we have solved the system of differential equations
provided by the 6 x 6 Luttinger Hamiltonian [1] simultaneously with the Poisson
equation, applying an iterative process until convergence was achieved. This enabled us
to incorporate the warping and the strong coupling among the subbands that constitute
the band structure [2].

From the calculated density of carriers we were able to evaluate an average effective
mass. Although our calculations indicate that this effective mass varies notably with the
hole confinement level, in general, we observed a decrease in the calculated effective
mass as the molar fraction of Ge increases, which might justify the use of this kind of
device.
An Analytic Expression of Thermal DiffusionCoefficient for the Hydrodynamic Simulationof Semiconductor Devices
Authors: Tang Ting-Wei , Wang Xinlin , Gan Haitao , Ieong Meikei
Published: September 2007

A new analytical expression of thermal diffusion coefficient DT is derived. To the firstorder
approximation, it is given by (1+η)-1(D/Tn) rather than (1–η)(D/Tn) where
η=–(Tn/η*)(∂η*/∂Tn
) and η* represents the temperature‐dependent bulk mobility.
This new transport coefficient is implemented in our 2‐D hydrodynamic device
simulator and it seems to produce more reasonable results.
A Backward Monte Carlo Method for Simulationof the Electron Quantum Kinetics in Semiconductors
Authors: Nedjalkov M. , Kosina H. , Selberherr S. , Dimov I.
Published: September 2007

A quantum‐kinetic equation accounting for the electron‐phonon interaction is solved by
a stochastic approach. Analyzed are three analytically equivalent integral formulation
of the equation which appear to have different numerical properties. Particularly the
path‐integral formulation is found to be advantageous for the numerical treatment. The
analysis is supported by the presented simulation results. A variety of physical effects
such as collisional broadening and collision retardation introduced by the equation are
discussed.
Detection of Quantum Cellular AutomatonAction in Silicon‐on‐insulator Cells
Authors: Gattobigio M. , Macucci M. , Iannaccone G.
Published: September 2007

We present a proposal for an experiment to demonstrate QCA (Quantum Cellular
Automaton) functionality for a cell fabricated with silicon‐on‐insulator technology. The
fundamental feature of a working QCA cell consists in the anticorrelated transition of
electrons in the two pairs of dots forming the cell: we show how such a phenomenon can
be detected from the appearance of a “locking” effect between the Coulomb Blockade
current peaks relative to each pair. The proposed approach allows the detection of QCA
action without the need for additional noninvasive charge detectors probing each dot.
We have performed detailed numerical simulations on the basis of interdot capacitance
values obtained from experimental data and determined the range of parameters within
which the effect should be detectable.
Monte Carlo Study of the Lateral Distributionof Gate Current Density Along the Channelof Submicron LDD MOSFET′s
Authors: Harkar A. , Kelsall R. W. , Ellis J. N.
Published: September 2007

This paper presents the spatial distribution of hot electrons along the channel of a
0.35 micron MOSFET using the full band pseudopotential Monte Carlo simulator
DAMOCLES. The important aspect of this investigation is the implementation of a
rigorous statistical enhancement technique along the channel of the device, to probe the
hot electrons generated along the channel. Simulations have been carried out for different
bias points. The results clearly show that the probability of generating electrons with
energies sufficient for injection into the oxide layer is significant only at the drain side of
the device. It is also observed that the peak gate current occurs exactly just inside the
LDD region coincident with the position of maximum lateral electric field.
A Systematic Approach to Reduce the System Bus Load and Power in Multimedia Algorithms
Authors: Danckaert Koen , Kulkarni Chidamber , Catthoor Francky , De Man Hugo , Tiwari Vivek
Published: September 2007

Multimedia algorithms deal with enormous amounts of data transfers and storage,
resulting in huge bandwidth requirements at the off‐chip memory and system bus level.
As a result the related energy consumption becomes critical. Even for execution time the
bottleneck can shift from the CPU to the external bus load. This paper demonstrates
a systematic software approach to reduce this system bus load. It consists of source‐to‐source
code transformations, that have to be applied before the conventional ILP
compilation. To illustrate this we use a cavity detection algorithm for medical imaging,
that is mapped on an Intel Pentium® II processor.
Soft Sphere Model for Electron Correlationand Scattering in the Atomistic Modellingof Semiconductor Devices
Authors: Watling J. R. , Barker J. R. , Asenov A.
Published: September 2007

As MOSFET devices within the deep sub‐micron regime are modelled, it is no longer
feasible to represent the charged dopants by a continuous charge distribution. In this
regime an ensemble of devices, each with different spatial distributions and the number
of dopants, must be modelled. However, it is computationally prohibitive to solve for
the full Coulomb interaction required for particle simulators, especially for an ensemble
of devices. To address this point, the paper focuses on the issue of modelling the
dynamics in the presence of discrete carrier–carrier scattering and carrier‐fixed impurity
scattering which is suitable for efficient simulations of large ensembles of devices.
Influence of Electron‐Electron Interactionon Electron Distributions in Short Si‐MOSFETsAnalysed Using the Local IterativeMonte Carlo Technique
Authors: Mietzner T. , Jakumeit J. , Ravaioli U.
Published: September 2007

The effects of electron–electron interaction on the electron distribution in n‐channel
metal‐oxide‐semiconductor field‐effect transistors (MOSFETs) are studied using the
Local Iterative Monte Carlo (LIMO) technique. This work demonstrates that electron–electron
scattering can be efficiently treated within this technique. The simulation results
of a 90 nm Si‐MOSFET are presented. We observe an increase of the high energy tail of
the electron distribution at the transition from channel to drain.
Accurate Power Estimation for Sequential CMOS Circuits Using Graph‐based Methods
Authors: Leeser Miriam , Ohm Valerie
Published: September 2007

We present a novel method for estimating the power of sequential CMOS circuits.
Symbolic probabilistic power estimation with an enumerated state space is used to
estimate the average power switched by the circuit. This approach is more accurate than
simulation based methods. Automatic circuit partitioning and state space exploration
provide improvements in run‐time and storage requirements over existing approaches.
Circuits are automatically partitioned to improve the execution time and to allow larger
circuits to be processed. Spatial correlation is dealt with by minimizing the cutset
between partitions which tends to keep areas of reconvergent fanout in the same
partition. Circuit partitions can be recombined using our combinational estimation
methods which allow the exploitation of knowledge of probabilities of the circuit inputs.
We enumerate the state transition graph (STG) incrementally using state space
exploration methods developed for formal verification. Portions of the STG are
generated on an as‐needed basis, and thrown away after they are processed. BDDs are
used to compactly represent similar states. This saves significant space in the storage of
the STG. Our results show that modeling the state space is imperative for accurate
power estimation of sequential circuits, partitioning saves time, and incremental state
space exploration saves storage space. This allows us to process larger circuits than
would otherwise be possible
Langevin Forces and Generalized Transfer Fields forNoise Modelling in Deep Submicron Devices
Authors: Shiktorov P. , Starikov E. , Gruzinskis V. , GonzáLez T. , Mateos J. , Pardo D. , Reggiani L. , Varani L. , Vaissiére J. C.
Published: September 2007

We present a generalized transfer field method with the microscopic noise sources
directly connected with the velocity and energy change during single scattering events.
The advantages of this method are illustrated by hydrodynamic calculations of current
and voltage noise spectra in several two‐terminal submicron structures.
Simulation of Drastic Lag Phenomena in GaAs‐Based FETs for Large Voltage Swing
Authors: Horio K. , Mitani Y. , Wakabayashi A. , Kurosawa N.
Published: September 2007

Turn‐on characteristics of GaAs MESFETs and HEMTs are simulated when the gate voltage is changed abruptly. The gate‐lag or slow current transient becomes more pronounced when the off‐state gate voltage is more negative, because the surface‐state effects or substrate‐trap effects become more significant. Changes of I–V curves of GaAs MESFETs, when the drain voltage is swept with different speeds, are also simulated. When the swept time is short, the curve shows overshoot‐like behavior and the kink disappears, indicating that the I–V characteristics should be quite different between DC and RF conditions.
Low Power Design for ASIC Cores
Authors: Dean Alvar , Garrett David , Stan Mircea R. , Ventrone Sebastian
Published: September 2007

A semicustom ASIC design methodology is used to develop a low power DSP core for
mobile (battery powered) applications. Different low power design techniques are used,
including dual voltage, low power library elements, accurate power reporting, pseudomicrocode,
transition‐once logic, clock gating, and others.