Uniaxial-process-induced strained-Si: extending the CMOS roadmap

This paper reviews the history of strained-silicon and the adoption of uniaxial-process-induced strain in nearly all high-performance 90-, 65-, and 45-nm logic technologies to date. A more complete data set of n- and p-channel MOSFET piezoresistance and strain-altered gate tunneling is presented along with new insight into the physical mechanisms responsible for hole mobility enhancement. Strained-Si hole mobility data are analyzed using six band k/spl middot/p calculations for stresses of technological importance: uniaxial longitudinal compressive and biaxial stress on [001] and [110] wafers. The calculations and experimental data show that low in-plane and large out-of-plane conductivity effective masses and a high density of states in the top band are all important for large hole mobility enhancement. This work suggests longitudinal compressive stress on [001] or [110] wafers and <110> channel direction offers the most favorable band structure for holes. The maximum Si inversion-layer hole mobility enhancement is estimated to be /spl sim/ 4 times higher for uniaxial stress on (100) wafer and /spl sim/ 2 times higher for biaxial stress on (100) wafer and for uniaxial stress on a [110] wafer.     

Optimal buffered compression and coding mode selection for MPEG-4shape coding

We propose an optimal buffered compression algorithm for shape coding as defined in the forthcoming MPEG-4 international standard. The MPEG-4 shape coding scheme consists of two steps: first, distortion is introduced by down and up scaling; then, context-based arithmetic encoding is applied. Since arithmetic coding is "lossless," the down up scaling step is considered as a virtual quantizer. We first formulate the buffer-constrained adaptive quantization problem for shape coding, and then propose an algorithm for the optimal solution under buffer constraints. Previously, the fact that a conversion ratio (CR) of 1/4 makes a coded image irritating to human observers for QCIF size was reported for MPEG-4 shape coding. Therefore, careful consideration for small size images such as QCIF should be given to prevent coded images from being unacceptable. To this end, a low bit rate tuned algorithm is proposed in this paper as well. Experimental results are given using an MPEG-4 shape codec.     

Empirical equations on electrical parameters of coupled microstriplines for crosstalk estimation in printed circuit board

Empirical equations for the self and mutual capacitance and inductance (C_s, C_m, L_s, L_m) of coupled microstrip lines in a printed circuit board were derived from the numerical simulation results to reduce the computation time for crosstalk estimation. Comparison of the measured C_s, C_m , L_s and L_m values with the derived empirical equations showed good agreements. Also in the near-end and far-end crosstalks, good agreements were obtained between measurements and the derived empirical equations. Microstrip lines embedded in the homogeneous dielectric material as well as those in the inhomogeneous medium with one side exposed to air were considered in this work. Based on the derived empirical equations, a design guide on the spacing between microstrip lines was established     

Ag Nanowire Reinforced Highly Stretchable Conductive Fibers for Wearable Electronics

Stretchable conductive fibers have received significant attention due to their possibility of being utilized in wearable and foldable electronics. Here, highly stretchable conductive fiber composed of silver nanowires (AgNWs) and silver nanoparticles (AgNPs) embedded in a styrene–butadiene–styrene (SBS) elastomeric matrix is fabricated. An AgNW‐embedded SBS fiber is fabricated by a simple wet spinning method. Then, the AgNPs are formed on both the surface and inner region of the AgNW‐embedded fiber via repeated cycles of silver precursor absorption and reduction processes. The AgNW‐embedded conductive fiber exhibits superior initial electrical conductivity (σ₀ = 2450 S cm^?1) and elongation at break (900% strain) due to the high weight percentage of the conductive fillers and the use of a highly stretchable SBS elastomer matrix. During the stretching, the embedded AgNWs act as conducting bridges between AgNPs, resulting in the preservation of electrical conductivity under high strain (the rate of conductivity degradation, σ/σ₀ = 4.4% at 100% strain). The AgNW‐embedded conductive fibers show the strain‐sensing behavior with a broad range of applied tensile strain. The AgNW reinforced highly stretchable conductive fibers can be embedded into a smart glove for detecting sign language by integrating five composite fibers in the glove, which can successfully perceive human motions.     

Unveiled Ferroelectricity in Well-Known Non-Ferroelectric Materials and Their Semiconductor Applications

Ferroelectric materials are considered ideal for emerging memory devices owing to their characteristic remanent polarization, which can be switched by applying a sufficient electric field. However, even several decades after the initial conceptualization of ferroelectric memory, its applications are limited to a niche market. The slow advancement of ferroelectric memories can be attributed to several extant issues, such as the absence of ferroelectric materials with complementary metal–oxide–semiconductor (CMOS) compatibility and scalability. Since the 2010s, ferroelectric memories have attracted increasing interest because of newly discovered ferroelectricity in well-established CMOS-compatible materials, which are previously known to be non-ferroelectric, such as fluorite-structured (Hf,Zr)O₂ and wurtzite-structured (Al,Sc)N. With advancing material fabrication technologies, for example, accurate chemical doping and atomic-level thickness control, a metastable polar phase, and switchable polarization with a reasonable electric field can be induced in (Hf,Zr)O₂ and (Al,Sc)N. Nonetheless, various issues still exist that urgently require solutions to facilitate the use of the ferroelectric (Hf,Zr)O₂ and (Al,Sc)N in emerging memory devices. Thus, ferroelectric (Hf,Zr)O₂ and (Al,Sc)N are comprehensively reviewed herein, including their fundamental science and practical applications.     

Empirical analysis of strategy selection for the technology leading and technology catch-up in the IT industry

R&D strategies of companies with low and high technological levels are discussed based on the concept of technology convergence and divergence. However, empirically detecting enterprise technology convergence in the distribution of enterprise technology (total productivity increase) over time and identifying key change factors are challenging. This study used a novel statistical indicator that captures the internal technology distribution change with a single number to clearly measure the technology distribution peak as a change in critical bandwidth for enterprise technology convergence and presented it as evidence of each technology convergence or divergence. Furthermore, this study applied the quantitative technology convergence identification method. Technology convergence appeared from the separation of total corporate productivity distribution of 69 IT companies in Korea in 2019–2020 rather than in 2015–2016. Results indicated that when the total technological level was separated from the technology leading and technology catch-up, IT companies were found to be pursuing R&D strategies for technology catch-up.     

Personalized Healthcare System for Chronic Disease Care in Cloud Environment

The rapid increase in the number of patients with chronic diseases is an important public healthcare issue in many countries, which accelerates many studies on a healthcare system that can, whenever and wherever, extract and process patient data. A patient with a chronic disease conducts self‐management in an out‐of‐hospital environment, particularly in an at‐home environment, so it is important to provide integrated and personalized healthcare services for effective care. To help provide effective care for chronic disease patients, we propose a service flow and a new cloud‐based personalized healthcare system architecture supporting both at‐home and at‐hospital environments. The system considers the different characteristics of at‐hospital and at‐home environments, and it provides various chronic disease care services. A prototype implementation and a predicted cost model are provided to show the effectiveness of the system. The proposed personalized healthcare system can support cost‐effective disease care in an at‐hospital environment and personalized self‐management of chronic disease in an at‐home environment.     

High-Performance and Low-Cost Single-Switch Current-Fed Energy Recovery Circuit for ac Plasma Display Panel

A high-performance and low-cost single-switch current-fed energy recovery circuit (ERC) for an alternating current (ac) plasma display panel (PDF) is proposed. Since it is composed of only one power switch compared with the conventional circuit consisting of four power switches and two large energy recovery capacitors, it features a much simpler structure and lower cost. Furthermore, since all power switches can be switched under soft-switching operation, the proposed circuit has desirable merits such as an increased reliability, and low switching loss. Especially, there are no serious voltage notches across the PDP with the aid of gas discharge current compensation, which can greatly reduce the current stress of all inverter switches, and provide those switches with the turn on timing margin. To confirm the validity of the proposed circuit, its operation and performance were verified on a prototype for 7-in test PDP.     

Consideration of the Actual Current-Spreading Length of GaN-Based Light-Emitting Diodes for High-Efficiency Design

Based on the proposed experimental method, the current spreading length of GaN-based light-emitting diodes (LEDs) was measured and analyzed for practical device design. In this study, Thompson's and Guo's models, which are categorized according to vertical series resistance (in particular, p-type contact resistance), were used to extract device parameters. It was shown that the measured current spreading length strongly depends on the injected current density. For LEDs fabricated with low-resistance p-type contacts, this behavior could be explained in terms of the accelerated current crowding with higher current densities occurring as a result of the reduced voltage drop across the junction, which is in good agreement with Thompson's relation. However, for LEDs fabricated with high-resistance p-contacts, unlike Guo's prediction, the measured current spreading length also showed a strong dependence on the injected current density. This was attributed to thermal heating at the p-contact, resulting in the reduction of the voltage drop across the p-contact and so junction voltage, which is also in agreement with Thompson's model. Based on the measured parameters and the design rule, efficient p-type reflectors, namely, hybrid reflectors were designed. Compared with conventional ones, LEDs fabricated with the hybrid reflectors exhibited better output power at a reasonable forward voltage, indicating that the proposed method is effective in understanding the actual current spreading and hence the practical design of high-efficiency LEDs.     

On detecting the presence of fetal R-wave using the moving averagedmagnitude difference algorithm

An efficient algorithm detecting the presence of a fetal QRS complex is presented. The proposed fetal QRS detection method computes the averaged magnitude of the difference between the fetal ECG signal and the reference signal to detect the fetal QRS event. The detected fetal QRS complexes are exponentially averaged to generate the template signal which can track the slowly varying shape of the fetal ECG signal. As an effort to obtain improved detection performances, two approaches of normalizing the fetal ECG signal and the template are considered.