Said F. Al-Sarawi

A review of 3-D packaging technology

This paper reviews the state-of-the-art in three-dimensional (3-D) packaging technology for very large scale integration (VLSI). A number of bare dice and multichip module (MCM) stacking technologies are emerging to meet the ever increasing demands for low power consumption, low weight and compact portable systems. Vertical interconnect techniques are reviewed in detail. Technical issues such as silicon efficiency, complexity, thermal management, interconnection density, speed, power etc. are critical in the choice of 3-D stacking technology, depending on the target application, and are briefly discussed.

High-Sensitivity Metamaterial-Inspired Sensor for Microfluidic Dielectric Characterization

A new metamaterial-inspired microwave microfluidic sensor is proposed in this paper. The main part of the device is a microstrip coupled complementary split-ring resonator (CSRR). At resonance, a strong electric field will be established along the sides of CSRR producing a very sensitive area to a change in the nearby dielectric material. A micro-channel is positioned over this area for microfluidic sensing. The liquid sample flowing inside the channel modifies the resonance frequency and peak attenuation of the CSRR resonance. The dielectric properties of the liquid sample can be estimated by establishing an empirical relation between the resonance characteristics and the sample complex permittivity. The designed microfluidic sensor requires a very small amount of sample for testing since the cross-sectional area of the sensing channel is over five orders of magnitude smaller than the square of the wavelength. The proposed microfluidic sensing concept is compatible with lab-on-a-chip platforms owing to its compactness.

The fourth element: characteristics, modelling and electromagnetic theory of the memristor

In 2008, researchers at the Hewlett–Packard (HP) laboratories published a paper in Nature reporting the development of a new basic circuit element that completes the missing link between charge and flux linkage, which was postulated by Chua in 1971 (Chua 1971 IEEE Trans. Circuit Theory 18, 507–519 (doi:10.1109/TCT.1971.1083337)). The HP memristor is based on a nanometre scale TiO2 thin film, containing a— doped region and an undoped region. Further to proposed applications of memristors in artificial biological systems and non-volatile RAM, they also enable reconfigurable nanoelectronics. Moreover, memristors provide new paradigms in application-specific integrated circuits and field programmable gate arrays. A significant reduction in area with an unprecedented memory capacity and device density are the potential advantages of memristors for integrated circuits. This work reviews the memristor and provides mathematical and SPICE models for memristors. Insight into the memristor device is given via recalling the quasi-static expansion of Maxwell’s equations. We also review Chua’s arguments based on electromagnetic theory.

Displacement Sensor Based on Diamond-Shaped Tapered Split Ring Resonator

Split-ring resonators (SRRs) are ideal structures for the realization of compact high-sensitivity and high-resolution sensors due to their high-quality factor resonance, compact size, and high sensitivity to changes in the constituent materials and physical dimensions. This paper presents a displacement sensor based on a diamond-shaped tapered SRR coupled to a coplanar waveguide. Two significant improvements over previous designs are reported. Firstly, the proposed sensor has higher dynamic range and linearity for displacement sensing. Secondly, compared with previous designs, where the displacement changes both the resonant frequency and depth of the transmission notch, the proposed sensor has a fixed resonant frequency. This is an important improvement since the sensor can be operated at a single fixed frequency and bypass the need for a frequency-sweeping microwave source and measurement system such as an expensive network analyzer. It is shown that, while preserving the compact size, the proposed sensor also benefits from a lower operating frequency. The design principle and simulation results are validated through measurement.

Memristive Device Fundamentals and Modeling: Applications to Circuits and Systems Simulation

The nonvolatile memory property of a memristor enables the realization of new methods for a variety of computational engines ranging from innovative memristive-based neuromorphic circuitry through to advanced memory applications. The nanometer-scale feature of the device creates a new opportunity for realization of innovative circuits that in some cases are not possible or have inefficient realization in the present and established design domain. The nature of the boundary, the complexity of the ionic transport and tunneling mechanism, and the nanoscale feature of the memristor introduces challenges in modeling, characterization, and simulation of future circuits and systems. Here, a deeper insight is gained in understanding the device operation, leading to the development of practical models that can be implemented in current computer-aided design (CAD) tools.

An Analytical Approach for Memristive Nanoarchitectures

As conventional memory technologies are challenged by their technological physical limits, emerging technologies driven by novel materials are becoming an attractive option for future memory architectures. Among these technologies, Resistive Memories (ReRAM) created new possibilities because of their nanofeatures and unique I-V characteristics. One particular problem that limits the maximum array size is interference from neighboring cells due to sneak-path currents. A possible device level solution to address this issue is to implement a memory array using complementary resistive switches (CRS). Although the storage mechanism for a CRS is fundamentally different from what has been reported for memristors (low and high resistances), a CRS is simply formed by two series bipolar memristors with opposing polarities. In this paper, our intention is to introduce modeling principles that have been previously verified through measurements and extend the simulation principles based on memristors to CRS devices and, hence, provide an analytical approach to the design of a CRS array. The presented approach creates the necessary design methodology platform that will assist designers in implementation of CRS devices in future systems.

Spike-Based Synaptic Plasticity in Silicon: Design, Implementation, Application, and Challenges

The ability to carry out signal processing, classification, recognition, and computation in artificial spiking neural networks (SNNs) is mediated by their synapses. In particular, through activity-dependent alteration of their efficacies, synapses play a fundamental role in learning. The mathematical prescriptions under which synapses modify their weights are termed synaptic plasticity rules. These learning rules can be based on abstract computational neuroscience models or on detailed biophysical ones. As these rules are being proposed and developed by experimental and computational neuroscientists, engineers strive to design and implement them in silicon and en masse in order to employ them in complex real-world applications. In this paper, we describe analog very large-scale integration (VLSI) circuit implementations of multiple synaptic plasticity rules, ranging from phenomenological ones (e.g., based on spike timing, mean firing rates, or both) to biophysically realistic ones (e.g., calcium-dependent models). We discuss the application domains, weaknesses, and strengths of various representative approaches proposed in the literature, and provide insight into the challenges that engineers face when designing and implementing synaptic plasticity rules in VLSI technology for utilizing them in real-world applications.

Metamaterial-Inspired Rotation Sensor With Wide Dynamic Range

A rotation sensor with a wide dynamic range is designed based on tapered U-shaped resonators. The proposed device is composed of a rounded microstrip transmission line that couples to two meandered resonators that are stacked on top of each other. By rotating the upper resonator, the overlapping area between the two resonators is increased causing a stronger coupling that shifts down the resonance frequency of the device. This frequency shift can be read out in the transmission response from which the rotation angle is determined. The operation principle of the sensor is explained in detail by using a circuit model. A sensor prototype is designed for the microwave frequency range and an experiment is presented for validating the proposed sensing approach. This sensing device is well suited for further miniaturization using microelectromechanical systems technology.

Memristive crypto primitive for building highly secure physical unclonable functions.

Physical unclonable functions (PUFs) exploit the intrinsic complexity and irreproducibility of physical systems to generate secret information. The advantage is that PUFs have the potential to provide fundamentally higher security than traditional cryptographic methods by preventing the cloning of devices and the extraction of secret keys. Most PUF designs focus on exploiting process variations in Complementary Metal Oxide Semiconductor (CMOS) technology. In recent years, progress in nanoelectronic devices such as memristors has demonstrated the prevalence of process variations in scaling electronics down to the nano region. In this paper, we exploit the extremely large information density available in nanocrossbar architectures and the significant resistance variations of memristors to develop an on-chip memristive device based strong PUF (mrSPUF). Our novel architecture demonstrates desirable characteristics of PUFs, including uniqueness, reliability, and large number of challenge-response pairs (CRPs) and desirable characteristics of strong PUFs. More significantly, in contrast to most existing PUFs, our PUF can act as a reconfigurable PUF (rPUF) without additional hardware and is of benefit to applications needing revocation or update of secure key information.

Second-Order Terahertz Bandpass Frequency Selective Surface With Miniaturized Elements

In this paper, a second-order frequency selective surface (FSS) made of miniaturized elements is proposed and designed for terahertz applications. The FSS is composed of two layers of metallic arrays separated from each other by a polymer dielectric spacer. The unit cells on the front and back layers are smaller than λ0/5, where λ0 is the free space wavelength. The operation principle of the proposed FSS is described through a circuit model, and a synthesis procedure is presented for designing a desired filtering response. A prototype of the FSS is synthesized to operate at a center frequency of 0.42 THz with 45% fractional bandwidth. The designed FSS is fabricated by using microfabrication process. The performance is evaluated by using terahertz time-domain spectroscopy. Measurement results show a low sensitivity of the FSS response to oblique angles of incidence for both of the TE and TM polarizations.