Wolfgang Fichtner's research while affiliated with ETH Zurich and other places

Publications (210)

Article
Accurate transient temperature prediction in GaN devices is an increasingly important process in the design of dependable radio frequency systems. In this paper, a methodology for dynamic electro-thermal simulation of GaN microwave and power devices is presented, which bases on the extraction of compact thermal models by three-dimensional finite el...
Conference Paper
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We present a multi-dimensional, atomistic, quantum transport simulation approach to investigate the performances of realistic nanoscale transistors for various geometries and material systems. The central computation consists in solving the Schrödinger equation with open boundary conditions several thousand times. To do that, a Wave Function approa...
Article
Scanning electron microscopy is still the technique of choice for imaging and for in-line measurement of critical dimensions and overlay accuracy in most of the core technology processes. In particular, critical dimension microscopy provides information about design template matching and edge placement errors through links with design having proven...
Article
Emerging applications like solar, automotive, railway traction, and nuclear impose to electrical cables increased performances in terms of dependability. Therefore, new tools and procedures are needed to design manufacturing processes for improved reliability and less parameter variability. This paper demonstrates the use of a dedicated simulation...
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We have developed a novel methodology to design systems composed of complementary metal-oxide-semiconductor (CMOS) and microelectromechanical systems (MEMS) parts. This multiscale methodology combines bottom-up modeling and top-down design-space exploration through the following steps: 1) In bottom-up modeling, characteristics of CMOS circuits and...
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Efficient screening procedures for the control of defectivity are vital to limit early failures, particularly in critical automotive applications. Traditional strategies based on burn-in and in-line tests are able to provide the required level of reliability, but they are expensive and time consuming. This paper presents a novel built-in circuitry...
Article
Full-text available
Efficient screening procedures for the control of the defectivity are vital to limit early failures especially in critical automotive applications. Traditional strategies based on burn-in and in-line tests are able to provide the required level of reliability but they are expensive and time consuming. This paper presents a novel built-in reliabilit...
Conference Paper
The forthcoming IEEE 802.3ba Ethernet standard will provide data transmission at a bandwidth of 100 Gbit/s. Currently, the fastest cryptographic primitive approved by the U.S. National Institute for Standard and Technology, that combines data encryption and authentication, is the Galois/Counter Mode (GCM) of operation. If the feasibility to increas...
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Traditional procedures for the extraction of mechanical properties of thin films by nanoindentation measurements have shown problems in terms of accuracy and in the ability to support sophisticated constitutive models. In this paper, an inverse modeling procedure based on finite element analysis is presented to solve these limitations. Finite eleme...
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A novel built-in approach is proposed to screen out defects in the array of capacitors and control logic of Successive Approximation Register Analog to Digital Converters. This technique is based on an embedded circuitry for the configuration, the stressing and for an accurate and fast leakage current measurement. The built-in screening system redu...
Article
Modeling of critical dimensions scanning electron microscopy with sub-nanometer uncertainty is required to provide a metrics and to avoid yield loss in the processing of advanced CMOS technologies. In this paper, a new approach is proposed, which includes a new Monte Carlo scheme, a new Monte Carlo code, as well as the coupling with electrostatic f...
Conference Paper
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In this paper, the validity of the dose ratio criterion to define the optimum processing conditions for electron crosslinking of electric cables and wires is investigated. The energy values obtained by different calculation procedures are correlated to the results obtained by simulation with a realistic three-dimensional Monte Carlo model in conjun...
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Besides the use of the most sophisticated equipment, accurate nanometrology for the most advanced CMOS processes requires that the physics of image formation in scanning electron microscopy (SEM) being modeled to extract critical dimensions. In this paper, a novel Monte Carlo simulation code based on the energy straggling principle is presented, wh...
Article
We investigated the diffusion of arsenic (As) in [100]-uniaxially compressive and tensile stressed silicon with density functional simulations, for stress values up to 1.8 GPa. At a temperature of 1000 °C, the diffusion coefficient of the most prevalent As vacancy pair (As-V) was found to be up to eight times higher in compressively strained silico...
Article
Galvanic coupling is a promising approach for wireless intrabody data transmission between sensors. Using the human body as a transmission medium for electrical signals becomes a novel data communication technique in biomedical monitoring systems. In this paper, special attention is given to the coupling of the current into the human body. Safety r...
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The main scattering mechanisms governing the transport of electrons in PMMA in an energy domain ranging from the energy of the primary electron beam down to few hundreds of meV are identified. A quantitative Monte Carlo model for the emission of secondary electrons is developed to be applied for critical dimensions extraction from high-resolution s...
Article
This paper describes the implementation of the hard computational kernels required for the baseband (BB) processing of a 2×2 multiple-input multiple-output (MIMO)-OFDM receiver on a design-framework for application specific processors. The employed low-complexity BB algorithms are described and their computational complexity is derived. The receive...
Article
The reliability of electric cables and wires using electron beam crosslinked polymers as isolator materials strongly depends on the accuracy in predicting the dose deposited during irradiation. This paper presents the main reliability issues that can be encountered in field operation, experimental data showing the criticality of the dose parameter,...
Article
Efficient screening procedures for the control of the defectivity are vital to limit early failures especially in critical automotive applications. Traditional strategies based on burn-in and in-line tests are able to provide the required level of reliability but they are expensive and time consuming. This paper presents a novel built-in reliabilit...
Article
Galvanic coupling has been shown to be the best method for low-power on-body data transmission. This approach has been extended toward wireless communication between implanted devices, building a real intrabody sensor network. To show the feasibility, a test system has been developed and implemented. The measurements are compared with the numerical...
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A multiscale simulation methodology is presented to predict the macroscopic mechanical properties of aluminum thin films with a columnar grain structure from the morphology at microscopic scale. The elasto–plastic characteristics of the thin films are calculated as a function of the grain size, temperature, and strain rate by taking into account cr...
Article
At the current stage of the SHA-3 competition organized by the U.S. National Institute of Standards and Technology (NIST), the 51 accepted candidates for the next-generation cryptographic hash standard SHA-3 are being evaluated in terms of security properties, computational efficiency, and memory requirements. While detailed information about the s...
Article
We present results of ab initio calculations for point defect clusters with phosphorus, arsenic, and antimony in silicon, including mixed clusters. We show that these dopant species interact, modifying their diffusion and activation. Most importantly, mixed clusters can exist in similar concentrations as pure clusters, reducing the fraction of acti...
Article
We determine the dominant mobile fluorine defect in silicon by density-functional based simulations. Among the mobile defects FV2, FV, F, and FI, we find the extra fluorine atom (F) to dominate diffusion. In p-type silicon it is neutral and in n-type silicon it is negatively charged. The calculated concentration of this defect is by a factor of at...
Conference Paper
A public competition organized by the NIST recently started, with the aim of identifying a new standard for cryptographic hashing (SHA-3). Besides a high security level, candidate algorithms should show good performance on various platforms. While an average performance on high-end processors is generally not critical, implementability and flexibil...
Conference Paper
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Efficient screening procedures for the control of the gate oxide defectivity are vital to limit early failures especially in critical automotive applications. Traditional strategies based on burn-in and in-line tests are able to provide the required level of reliability but they are expensive and time consuming. This paper presents a novel approach...
Conference Paper
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The goal of the demonstration is to show the visitor how MIMO-OFDM communication works and what gains in terms of throughput, link reliability, etc. can be achieved, visualized by different experiments.
Conference Paper
In the next years, new hash function candidates will replace the old MD5 and SHA-1 standards and the current SHA-2 family. The hash algorithms RadioGatún and irRUPT are potential successors based on a stream structure, which allows the achievement of high throughputs (particularly with long input messages) with minimal area occupation. In this pape...
Conference Paper
Software-defined radio (SDR) platforms represent a promising approach to facing the demands of the fast evolving field of wireless communications. The flexibility of SDR solutions is typically obtained at the cost of limited processing power, which imposes the use of low-complexity algorithms. This task is particularly challenging within multiple-i...
Conference Paper
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This paper provides an overview of a real-time multi-user multiple-input multiple-output (MIMO) communication testbed designed for demonstration and assessment of real-world wireless communication aspects. The testbed is built on a modular hardware platform consisting of three different boards and incorporates a MIMO-OFDM-based physical (PHY) layer...
Conference Paper
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This paper describes an efficient sparse linear solver for block tri-diagonal systems arising from atomistic device simulation based on the nearest-neighbor tight-binding method. The algorithms a parallel Gaussian elimination of blocks corresponding to atomic layers instead of single elements. It is known in the physics community as the renormaliza...
Article
The most widespread 16-bit multiplier architectures are compared in terms of area occupation, dissipated energy, and EDP (Energy-Delay Product) in view of low-power low-voltage signal processing for digital hearing aids and similar applications. Transistor-level simulations including back-annotated wire parasitics confirm that the propagation of gl...
Article
Various 16-bit multiplier architectures are compared in terms of dissipated energy, propagation delay, energy-delay product (EDP), and area occupation, in view of low-power low-voltage signal processing for low-frequency applications. A novel practical approach has been set up to investigate and graphically represent the mechanisms of glitch genera...
Conference Paper
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The gate currents of Si nanowire transistors are investigated using a three-dimensional, real-space, and self-consistent Schrodinger-Poisson solver. The influence of the gate material (metal or poly-Si) and the choice of the dielectric (SiO<sub>2</sub> or high- kappa stacks) are studied in details. Then, the performances of nanometer-scaled triple-...
Conference Paper
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Simulation is a well established support tool in the design, development and characterisation of power components and systems. However, technological advances are resulting in increasingly integrated devices, whose accurate virtual analysis is calling for novel approaches, offering enhanced flexibility. In this work, some interesting features of VH...
Article
Using the human body as a transmission medium for electrical signals offers novel data communication in biomedical monitoring systems. In this paper, galvanic coupling is presented as a promising approach for wireless intra-body communication between on-body sensors. The human body is characterized as a transmission medium for electrical current by...
Article
In this paper, we showed that the maximum active P concentration of approximately 2 times10<sup>20</sup> cm<sup>-3</sup> exists during solid-phase epitaxial recrystallization (SPER). This maximum active concentration is close to the reported values for other active impurity concentrations during SPER. We introduced the concept of an isolated impuri...
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The capabilities of three techniques to measure the transient average junction temperature in power MOS devices based on the electrical thermo-sensitive parameters are assessed experimentally and by compact device simulation. The first two methods make use of the dependency of dIds/dt on the temperature, while the third one exploits the temperature...
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Semiconductor nanowires are possible candidates to replace the metal-oxide-semiconductor field-effect transistors (MOSFET) since they can act both as active devices or as device connectors. In this article, the transmission coefficients of Si and GaAs nanowires with arbitrary transport directions and cross sections are simulated in the nearestneigh...
Article
The aggressive down-scaling in semiconductor devices implies the transistor voltage threshold reduction, which is associated with an exponential increase in sub-threshold leakage currents. For this reason, static power consumption is becoming the major issue of the newer technologies. A novel low-leakage technique (2Phi+sleep), which combines level...
Article
Diodes and diode strings in 90 nm and beyond technologies are investigated by measurement and device simulation. After a thorough calibration, the device simulator is utilised to achieve a better understanding and an enhanced device performance of diode strings under static and transient ESD conditions. Thereto, parasitic transistors and a so far n...
Conference Paper
Galvanic coupling provides a novel data transmission between sensor units for low frequency intra-body communication with electrodes attached to the human skin. In this work, that approach has been adapted to implantable miniaturized pills. A communication system for wireless data transmission in muscle tissue is developed capable of transmitting d...
Conference Paper
Monitoring of human vital functions is enabled by wireless technologies for distributed on-body mounted monitoring sensors. Galvanic coupling provides a novel data communication between sensors with coupling electrodes attached to the human skin. The next step is an implantable communication device. This study focuses on coupling strategies for int...
Conference Paper
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This paper proposes the development of a complete compact model of an IGBT-module, for use in a circuit simulation environment. The model includes all major electro-thermal effects and such features as the self-heating of the silicon dies and package related parasitic effects. An accurate selection of simulation examples, derived from a railway tra...
Conference Paper
Pilot-assisted channel estimation for communication systems employing orthogonal frequency division multiplexing modulation requires significant signal processing at the receiver if the correlation among the frequency-domain channel coefficients is to be exploited in order to improve accuracy. In this work, a conventional FFT processor is extended...
Conference Paper
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The QR decomposition is an important, but often underestimated prerequisite for pseudo- or non-linear detection methods such as successive interference cancellation or sphere decoding for multiple-input multiple-output (MIMO) systems. The ability of concurrent iterative sorting during the QR decomposition introduces a moderate overall latency, but...
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A study was conducted to analyze the importance of the dopant contrast in wide-bandgap semiconductors and the impact of relevant factors, such as surface effects and sample preparation, on the image quality. Scanning electron microscopy (SEM) was sed for getting secondary electron potential contrast (SEPC) for 2-D quantitative dopant imaging. The q...
Conference Paper
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Maximum likelihood (ML) detection provides optimum error rate performance for uncoded multiple-input multiple-output (MIMO) systems. However, circuit complexity of a straightforward implementation of ML detection is uneconomic for high-rate systems. This paper addresses the VLSI implementation trade-offs of a MIMO detection algorithm that achieves...
Article
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Nanowire transistors with a perfect crystal structure and a well-defined Si–SiO2 interface cannot be grown with the actual technology. The shape of the semiconducting channel varies from source to drain. By self-consistently coupling the three-dimensional Schrödinger and Poisson equations, interface roughness (IR) effects are studied in Si triple-g...
Conference Paper
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In this paper the current characteristics of Si triple-gate nanowire transistors are simulated for different channel orientations. The full-band properties of Si are taken into account via the semi-empirical sp<sup>3</sup>d<sup>5</sup>s* tight-binding method. The 3D electrostatic potential is solved self-consistently with the device charge density....
Chapter
Data communication between body mounted sensors is progressing towards wireless monitoring networks. In this work, digital data communication by galvanic coupling through the body is presented as a promising approach for wireless intra-body communication.
Chapter
Novel wireless communication networks for body mounted sensors explore the use of human tissue as a transmission medium. Electrical signal propagation through the human body requires a deep understanding of the dielectrical properties of human tissue. In this work, the dielectrical properties have been investigated to determine the pathway of curre...
Conference Paper
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In this paper, a generalization of tree-search algorithms with maximum likelihood (ML) error rate performance for the detection in multiple-input multiple-output (MIMO) systems is presented. The Schnorr-Euchner sphere decoder, Djikstra's algorithm applied to MIMO detection, and an ML- optimal variant of the K-best detector are shown to be special c...
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As the active dimensions of metal-oxide field-effect transistors are approaching the atomic scale, the electronic properties of these "nanowire" devices must be treated on a quantum mechanical level. In this paper, the transmission coefficients and the density of states of biased and unbiased Si and GaAs nanowires are simulated using the sp3d5s* em...
Conference Paper
Secondary electrons potential contrast (SEPC) by scanning electron microscopy has emerged as a powerful tool for two-dimensional quantitative dopant imaging. The main component of the SEPC signal arises from the difference in the built-in potential between differently doped regions; which is very high in wide-band-gap semiconductors and particularl...
Article
Dopant profiling and 2D imaging of device cross-sections have a strategic relevance for the development and for the failure analysis of new devices based on silicon carbide (SiC). Due to the extreme physical properties of SiC, the common electrical dopant profiling techniques have been shown to be poorly reliable. In this work, we report the latest...
Conference Paper
Two versions of a front-end circuit for hearing aids have been placed on the same die fabricated in 0.18¿m CMOS technology. The VHDL source code has been the same in either case. The difference has been in the set of standard cells made available to the synthesis tool. In the reference design, this has been a regular industrial cell library, while...
Conference Paper
Wavelet algorithms with subsequent encoders are used in the newest image compression standards such as JPEG2000 including EBCOT. The set partitioning in hierarchical trees (SPIHT) algorithm belongs to the next generation of encoders for wavelet-transformed images employing more sophisticated coding. SPIHT utilizes inherent redundancy among wavelet...
Conference Paper
A comprehensive study of spurious activity propagation, based on transistor-level simulations targeting a 0.18 CMOS process, is carried out in traditional multiplier architectures (Carry-Save, Carry-Save with Booth receding and Wallace tree). The results suggest to implement self-timed multipliers, i.e. multipliers in which partial products are tri...
Article
IGBT modules are critical components for the reliability of power converters used in traction applications. A thorough analysis of all stressful operating conditions is a complex task, which requires versatile simulation capability. In this paper a comprehensive electro-thermal model of an IGBT-module is developed. Then, circuit simulation is used...
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In this article, we study the coupled mode space approach to nonequilibrium Green’s function (NEGF) simulation. When the lateral confinement of nanoscale devices changes abruptly and the correlation functions arising from coupled mode effects are improperly evaluated in the current and charge density calculations, it becomes difficult to solve none...
Article
Secondary Electron Potential Contrast has been shown recently to be a very effective method for two-dimensional mapping the dopant distribution in Silicon Carbide devices. This work extends the range of applications of the technique to the characterization of photonic devices. Special attention is paid here to the analysis of unipolar and bipolar j...
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In this paper, the secondary electron dopant contrast in scanning electron microscopy is proposed as the method of choice for dopant imaging and profiling in silicon carbide devices. After reviewing the physical principles of the signal generation, the impact on the image quality of relevant factors such as experimental conditions, surface effects,...
Conference Paper
Glitches are responsible for a significant proportion of overall power dissipation in digital signal processing circuits. Activity-reduction techniques that involve an optimized clocking strategy have been applied to a front-end block in a DSP adaptive directional microphone for hearing aids. Functionally equivalent implementations, differing only...
Conference Paper
Using the human body as a transmission medium for electrical signals becomes a novel data communication technique in biomedical monitoring systems. Galvanical coupling is a promising approach for wireless intra-body data transmission between sensors. In this work, special attention is given to the coupling of the current into the human body. Safety...
Article
Full-text available
A number of devices, that are under investigation for implementing and calibrating physical models at high operating temperatures and transient high current stress, exhibit geometrical features that do not allow for the application of the standard Hall theory. This makes the outcome of measurements based on the Hall effect unreliable. A more genera...
Article
Data communication between body-mounted sensors is progressing towards wireless monitoring networks. In this work, digital data communication by galvanic coupling through the body is presented as a promising approach for wireless intra-body communication. The human body itself serves as the transmission medium of electrical current. Both binary and...
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Full-text available
In recent years several successful GALS realizations have been presented. The core of a GALS system is a locally synchronous island that is designed using industry standard synchronous design methodologies. In principle, any functional synchronous block can be encapsulated as a locally synchronous island to form a GALS module. There are, however, s...
Article
A new process optimization procedure is hereby presented, based on the quantitative impact of the variations of process variables on VLSI design performance. Process tuning is obtained through reverse modeling on transistor characteristics, process variations are then addressed by means of consistent TCAD simulations. Optimum process variables for...
Article
A new constant-coefficient FIR filter architecture is hereby presented, specifically designed for a VLSI adaptive directional microphone for hearing aids. Gate-level simulations targeting a 0.25 mum process point out relevant power savings compared to both the fully time-shared reference design (-80%) and a recently published low-power circuit (-32...
Conference Paper
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From an error rate performance perspective, maximum likelihood (ML) detection is the preferred detection method for multiple-input multiple-output (MIMO) communication systems. However, for high transmission rates a straight forward exhaustive search implementation suffers from prohibitive complexity. The K-best algorithm provides close-to-ML bit e...
Article
Two DSP algorithms for hearing aids have been integrated on silicon in a 0.18 mum CMOS process. Various level-sensitive two-phase clocking schemes have been evaluated in terms of energy efficiency. Actual measurements have confirmed energy savings of 64% over a recently published clock-gated single-edge-triggered one-phase implementation. Most of t...
Conference Paper
The performance of systems employing bit-interleaved coded modulation (BICM) critically depends on the availability of soft information. In the multi-antenna case, the extraction of optimum bit-metrics becomes prohibitively complex, so that suboptimal solutions need to be adopted for practical implementation. Instead of considering all the spatiall...
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One important requirement imposed on all eSTREAM stream cipher candidates was to show the potential to be superior to the AES in at least one significant aspect. We present hardware,implementation,results of eight different eSTREAM Profile-II candidates, all integrated in 0.25 µm 5-Metal CMOS technology. The goal of this work was to provide a fair...
Conference Paper
Resonant clocking holds the promise of trading speed for energy in CMOS circuits that can afford to operate at low frequency, like hearing aids. An experimental chip with 110k transistors and more than 2500 latches, has been designed, fabricated and tested. The measured energy con sumption of the design at 0.8 V is 62μW/MHz, about 7.5% less than th...
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The paper describes an algorithm and a corresponding VLSI architecture for the implementation of linear MMSE detection in packet-based MIMO-OFDM communication systems. The advantages of the presented receiver architecture are low latency, high-throughput, and efficient resource utilization, since the hardware required for the computation of the MMS...
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RESUMEN . RESUMEN In<sup> </sup>this paper useful physical objects called moments of the inverse<sup> </sup>scattering operator (MISO) of the Boltzmann equation (BE) are studied.<sup> </sup>The existence and uniqueness of the MISO is proven and<sup> </sup>a simple, generally valid, iterative scheme to actually compute those<sup> </sup>objects is...