Gate capacitances behavior of nanometer FD SOI CMOS devices with HfO/sub 2/ high-k gate dielectric considering vertical and fringing displacement effects using 2-D Simulation

This paper reports the gate-source (drain)/source (drain)-gate capacitance behavior of 100-nm fully depleted silicon-on-insulator CMOS devices with HfO/sub 2/ high-k gate dielectric considering vertical and fringing displacement effects. Based on the two-dimensional simulation results, a unique two-step C/sub S(D)G//C/sub GS/ versus V/sub G/ curve could be identified for the device with the 1.5-nm HfO/sub 2/ gate dielectric due to the vertical and fringing displacement effects.     

Gate tunneling leakage current behavior of 40 nm PD SOI NMOS device considering the floating body effect

This paper reports an analysis of floating body effect related gate tunneling leakage current behavior of the 40 nm PD SOI NMOS device using bipolar/MOS equivalent circuit approach. As confirmed by the experimentally measured data, the bipolar/MOS equivalent circuit approach could predict the gate tunneling leakage current behavior, which is strongly affected by the parasitic bipolar device in the floating body as observed from the perpendicular electric field along the path of the U-shaped edges of the polysilicon gate.     

用三维蒙特卡罗模拟栅-源/漏不对准对体硅FinFET器件性能的影响

We investigate the influence of gate-source/drain(G-S/D) misalignment on the performance of bulk fin field effect transistors(FinFETs) through the three-dimensional(3D) full band Monte Carlo simulator.Several scattering mechanisms,such as acoustic and optical phonon scattering,ionized impurity scattering,impact ionization scattering and surface roughness scattering are considered in our simulator.The influence of G-S/D overlap and underlap on the on-states performance and carrier transport of bulk FinFETs are mainly discussed in our work.Our results show that the on-states currents increase with the increment of G-D/S overlap length and the positions of a potential barrier and average electron energy maximum vary with the G-D/S overlap length.The carrier transport phenomena in bulk FinFETs are due to the effect of scattering and the electric field in the overlap/underlap regime.     

Analysis of floating substrate effects on the intrinsic gatecapacitance of SOI MOSFETSs using two-dimensional device simulation

Points out that the theoretical foundation of unique floating substrate effects, which have been observed experimentally, on the intrinsic gate capacitance characteristics of SOI n-MOSFETs has been clearly established using original two-dimensional device simulations. A transient simulation scheme for calculating intrinsic capacitances is introduced and tested against the classical quasi-static and small-signal analyses. The results are discussed and used to gain a deep physical insight into the basic mechanisms responsible for the anomalous (when compared to conventional bulk devices) intrinsic capacitances observed in the case of SOI MOSFETs. The analyses yields basic guidelines for an adequate analytical modeling of SOI MOSFET capacitive behavior to be used for accurate large- and small-signal simulation of SOI MOS digital and analog circuits     

Analysis of multifinger power HEMTs supported by effective 3-D device electrothermal simulation

The influence of the metallization layer geometry on the electrothermal behavior of the multifinger power high-electron mobility transistors (HEMTs) is studied. The analysis of thermal and electrical behavior is supported by effective 3-D electrothermal device simulation method developed for Synopsys TCAD Sentaurus environment using mixed-mode setup. The proposed methodology allows fast simulation of complex systems from individual semiconductor layers at a frontend up to package and cooling assemblies at a backend. More accurate electrothermal model of power HEMT is proposed and validated by finite element method (FEM) simulations. The analysis points on significant influence of metallization geometry design on electrothermal properties and reliability of the multifinger power HEMTs. The unique identification and visualization of the critical regions allows effective device optimization. Very good comparison between simulation results and experimental data demonstrate validity of the proposed simulation methodology and HEMT structures analysis.     

Modeling the effect of back gate bias on the subthreshold behavior of a SiGe-channel SOI PMOS device

This paper reports on a simulation study on the back gate bias effect on the subthreshold behavior of a SiGe-channel SOI PMOS device using a device simulator. With a SiGe channel, the SOI PMOS device shows a smaller back gate bias effect as compared to the one without it.     

Analysis of modes in a freestanding microsquare resonator by 3-D finite-difference time-domain simulation

Modes in a microsquare resonator slab with strong vertical waveguide consisting of air/semiconductor/air are analyzed by three-dimensional (3-D) finite-difference time-domain simulation, and compared with that of two-dimensional (2-D) simulation under effective index approximation. Mode frequencies and field distributions inside the resonator obtained by the 3-D simulation are in good agreement with those of the 2-D approximation. However, field distributions at the boundary of the resonator obtained by 3-D simulation are different from that of the 2-D simulation, especially the vertical field distribution near the boundary is great different from that of the slab waveguide, which is used in the effective index approximation. Furthermore the quality factors obtained by 3-D simulation are much larger than that by 2-D simulation for the square resonator slab with the strong vertical waveguide.     

Analysis of 3-D integral imaging displays using the Wigner distribution

Integral imaging is a promising technology for 3-D TV and 3-D display. In this paper, a theoretical analysis of 3-D integral imaging systems is performed in the frame of the Wigner distribution formalism. It is shown that the entire intensity distribution in the pick-up image plane of these systems can be obtained from a single 2-D Wigner distribution function of a single lenslet pupil. This result reveals the Wigner distribution function as a powerful tool for analysis of 3-D integral imaging systems with different pupil functions. As an example, the extension of the depth of field of an integral imaging system with lenslets having amplitude modulation (central obscuration) is proposed.     

Compression of hyperspectral imagery using the 3-D DCT and hybridDPCM/DCT

Two systems are presented for compression of hyperspectral imagery which utilize trellis coded quantization (TCQ). Specifically, the first system uses TCQ to encode transform coefficients resulting from the application of an 8×8×8 discrete cosine transform (DCT). The second systems uses DPCM to spectrally decorrelate the data, while a 2D DCT coding scheme is used for spatial decorrelation. Side information and rate allocation strategies are discussed. Entropy-constrained code-books are designed using a modified version of the generalized Lloyd algorithm. These entropy constrained systems achieve compression ratios of greater than 70:1 with average PSNRs of the coded hyperspectral sequences exceeding 40.0 dB     

An analysis of the difference in behavior of top and bottom contact organic thin film transistors using device simulation

This paper presents a systematic analysis of an already reported phenomenon, namely, the difference in device performance of top and bottom contact organic thin film transistors (OTFT) by combining experiments and two-dimensional device simulations. The mobility of the as measured devices in the bottom contact OTFT is found to be lower by two orders of magnitude than the top contact structure, which is generally attributed to the higher metal-semiconductor contact resistance in the bottom contact devices due to lower contact area. However, we found that this large mobility difference exists even after correcting for the metal-semiconductor contact resistance through transfer line method (TLM). This result suggests that structural differences are playing a dominant role in lowering down the performance of bottom contact devices. This effect is then systematically investigated through two-dimensional physics-based numerical simulations by considering several structural inhomogenities around the contacts. The main reason for such an occurrence is attributed to the poor morphology (or comparatively low mobility) of pentacene films around the source/drain electrodes in the bottom contact devices. Finally, we also show a reasonable match between the simulated and experimental device characteristics, enabling calibration of the simulator for further use in design of OTFTs.     

On the device design assessment of multigate FETs (MuGFETs) using full process and device simulation with 3D TCAD

A design evaluation is reported for multigate FETs (MuGFETs) by implementing a full process flow using a commercial three-dimensional technology CAD (TCAD) tool within the context of optimizing the device design and underlying fabrication processes. The simulation is based on and refers to the development of the SOI-based 30 nm MuGFET devices. Using our real process flow, various process simulation parameters from diffusion and activation models are first calibrated to the experimental data. Device simulations are then performed with varying fin doping, fin width, fin height, L_dd and halo implant tilt, and box thickness. For a given fin thickness and increasing fin height, the threshold voltage, off-current, delay and short channel effects (SCEs) remain approximately insensitive, while the on-current and transconductance increases approximately linearly with the increase in fin height. On the other hand drain-induced barrier lowering (DIBL), subthreshold slope (S) and off-current I_OFF are quite sensitive to the variations in fin width (at fixed fin height). We found that the lower L_dd and halo implant tilt angle (20–30°) are beneficial in reducing the SCEs and off-current. Finally, a comparison of the simulation results with electrical measurement data is presented, which shows fairly good agreement.     

On the blocking capability of a planar p-n junction under theinfluence of a high-voltage interconnection - a 3-D simulation

The routing of interconnections along the surface of a high-voltage IC presents one of the major issues for the IC designer. A special problem appears, if the interconnection can stay under a high-voltage signal and has to cross the boundaries of p-n junctions. In this paper, the influence of a high-voltage interconnection (HVI) on the blocking capability of a planar p-n junction including a JTE-design is investigated numerically by solving Poisson's equation under the depletion approximation. Recent 2-D simulations have shown, that a HVI crossing the space charge region within a distance smaller than 5 μm reduces the breakdown voltage drastically. However, these calculations ignored the limited lateral extension of real interconnection stripes and tend to overestimate its influence. As exhibited by the 3-D simulations in this paper, the influence of the stripe width can be ignored only for such structures, where the width of the stripe is in the same order of magnitude as the depletion layer width. For smaller stripe widths the influence of the HVI is lower. The dependence of the breakdown voltage on the stripe width is investigated for different distances between the HVI and the semiconductor surface     

Registration of 3-D intraoperative MR images of the brain using a finite-element biomechanical model

We present a new algorithm for the nonrigid registration of three-dimensional magnetic resonance (MR) intraoperative image sequences showing brain shift. The algorithm tracks key surfaces of objects (cortical surface and the lateral ventricles) in the image sequence using a deformable surface matching algorithm. The volumetric deformation field of the objects is then inferred from the displacements at the boundary surfaces using a linear elastic biomechanical finite-element model. Two experiments on synthetic image sequences are presented, as well as an initial experiment on intraoperative MR images showing brain shift. The results of the registration algorithm show a good correlation of the internal brain structures after deformation, and a good capability of measuring surface as well as subsurface shift. We measured distances between landmarks in the deformed initial image and the corresponding landmarks in the target scan. Cortical surface shifts of up to 10 mm and subsurface shifts of up to 6 mm were recovered with an accuracy of 1 mm or less and 3 mm or less respectively.     

A 3-D reconstruction system for the human jaw using a sequence of optical images

This paper presents a model-based vision system for dentistry that will assist in diagnosis, treatment planning, and surgical simulation. Dentistry requires an accurate three-dimensional (3-D) representation of the teeth and jaws for diagnostic and treatment purposes. The proposed integrated computer vision system constructs a 3-D model of the patient's dental occlusion using an intraoral video camera. A modified shape from shading (SFS) technique, using perspective projection and camera calibration, extracts the 3-D information from a sequence of two-dimensional (2-D) images of the jaw. Data fusion of range data and 3-D registration techniques develop the complete jaw model. Triangulation is then performed, and a solid 3-D model is reconstructed. The system performance is investigated using ground truth data, and the results show acceptable reconstruction accuracy.     

DOE/Opt: a system for design of experiments, response surfacemodeling, and optimization using process and device simulation

Rapid modeling and optimization of manufacturing processes, devices, and circuits are required to support modern integrated circuit technology development and yield improvement. We have prototyped and applied an integrated system, called DOE/Opt, for performing Design of Experiments (DOE), Response Surface Modeling (RSM), and Optimization (Opt). The system to be modeled and optimized can be either physical or simulation based. Within the DOE/Opt system, coupling to external simulation or experimental tools is achieved via an embedded extension language based on Tcl. The external problem then appears to DOE/Opt as a model with user defined inputs and outputs. DOE/Opt is used to generate splits for experiments, to dynamically build and evaluate regression models from experimental runs, and to perform nonlinear constrained optimizations using either regression models or embedded executions. The intermediate regression modeling can appreciably accelerate the optimization task when simulation or physical experiments are expensive. The primary application of DOE/Opt has been to process optimization using coupled process and device simulation. DOE/Opt has also been applied to process and device simulator tuning, and to aid in device characterization. Such a DOE/Opt system is expected to augment the use of TCAD tools and to utilize data collected by CIM systems in support of process synthesis. We have demonstrated the application of the system to process parameter determination, simulator tuning, process control modeling, and statistical process optimization. We are extending the system to more fully support emerging device design and process synthesis methodologies     

Accuracy and precision of the three-dimensional assessment of the facial surface using a 3-D laser scanner

Three-dimensional (3-D) recording of the surface of the human body or anatomical areas has gained importance in many medical specialties. Thus, it is important to determine scanner precision and accuracy in defined medical applications and to establish standards for the recording procedure. Here we evaluated the precision and accuracy of 3-D assessment of the facial area with the Minolta Vivid 910 3D Laser Scanner. We also investigated the influence of factors related to the recording procedure and the processing of scanner data on final results. These factors include lighting, alignment of scanner and object, the examiner, and the software used to convert measurements into virtual images. To assess scanner accuracy, we compared scanner data to those obtained by manual measurements on a dummy. Less than 7% of all results with the scanner method were outside a range of error of 2 mm when compared to corresponding reference measurements. Accuracy, thus, proved to be good enough to satisfy requirements for numerous clinical applications. Moreover, the experiments completed with the dummy yielded valuable information for optimizing recording parameters for best results. Thus, under defined conditions, precision and accuracy of surface models of the human face recorded with the Minolta Vivid 910 3D Scanner presumably can also be enhanced. Future studies will involve verification of our findings using test persons. The current findings indicate that the Minolta Vivid 910 3D Scanner might be used with benefit in medicine when recording the 3-D surface structures of the face.     

Suppression of the floating-body effect in SOI MOSFET's by thebandgap engineering method using a Si1-xGex sourcestructure

The bandgap engineering method using a SiGe source structure is presented as a means to suppress the floating-body effect in SOI MOSFET's. Experiments using Ge implantation are carried out to form a narrow-bandgapped SiGe layer in the source region. It has been confirmed that Ge-implanted SIMOX exhibited a 0.1 eV bandgap narrowing with a relatively low Ge-dosage of 10¹⁶ cm^-2. The fabricated N-type SOI-MOSFET's exhibited suppressed parasitic bipolar effects, such as improvement of the drain breakdown voltage or latch voltage, and suppression of abnormal subthreshold slope. Advantages over other conventional methods are also discussed, indicating that the bandgap engineering provides a practical method to suppress the floating-body effect     

Analysis of electrical characteristics of Au/SiO2/n-Si (MOS) capacitors using the high-low frequency capacitance and conductance methods

The purpose of this paper is to analyze electrical characteristics in Au/SiO₂/n-Si (MOS) capacitors by using the high-low frequency (C_HF-C_LF) capacitance and conductance methods. The capacitance-voltage (C-V) and conductance-voltage (G/ω-V) measurements have been carried out in the frequency range of 1 kHz-10 MHz and bias voltage range of (−12 V) to (12 V) at room temperature. It was found that both C and G/ω of the MOS capacitor were quite sensitive to frequency at relatively low frequencies, and decrease with increasing frequency. The increase in capacitance especially at low frequencies is resulting from the presence of interface states at Si/SiO₂ interface. Therefore, the interfacial states can more easily follow an ac signal at low frequencies, consequently, which contributes to the improvement of electrical properties of MOS capacitor. The interface states density (N_ss) have been determined by taking into account the surface potential as a function of applied bias. The energy density distribution profile of N_ss was obtained from C_HF-C_LF capacitance method and gives a peak at about the mid-gap of Si. In addition, the high frequency (1 MHz) capacitance and conductance values measured under both reverse and forward bias have been corrected for the effect of series resistance (R_s) to obtain the real capacitance of MOS capacitors. The frequency dependent C-V and G/ω-V characteristics confirm that the N_ss and R_s of the MOS capacitors are important parameters that strongly influence the electrical properties of MOS capacitors.