Design and Fabrication of Vertically-Integrated CMOS Image Sensors

Technologies to fabricate integrated circuits (IC) with 3D structures are an emerging trend in IC design. They are based on vertical stacking of active components to form heterogeneous microsystems. Electronic image sensors will benefit from these technologies because they allow increased pixel-level data processing and device optimization. This paper covers general principles in the design of vertically-integrated (VI) CMOS image sensors that are fabricated by flip-chip bonding. These sensors are composed of a CMOS die and a photodetector die. As a specific example, the paper presents a VI-CMOS image sensor that was designed at the University of Alberta, and fabricated with the help of CMC Microsystems and Micralyne Inc. To realize prototypes, CMOS dies with logarithmic active pixels were prepared in a commercial process, and photodetector dies with metal-semiconductor-metal devices were prepared in a custom process using hydrogenated amorphous silicon. The paper also describes a digital camera that was developed to test the prototype. In this camera, scenes captured by the image sensor are read using an FPGA board, and sent in real time to a PC over USB for data processing and display. Experimental results show that the VI-CMOS prototype has a higher dynamic range and a lower dark limit than conventional electronic image sensors

Nanoelectronics-Biology Frontier: From Nanoscopic Probes for Action Potential Recording in Live Cells to Three-Dimensional Cyborg Tissues

Semiconductor nanowires configured as the active channels of field-effect transistors (FETs) have been used as detectors for high-resolution electrical recording from single live cells, cell networks, tissues and organs. Extracellular measurements with substrate supported silicon nanowire (SiNW) FETs, which have projected active areas orders of magnitude smaller than conventional microfabricated multielectrode arrays (MEAs) and planar FETs, recorded action potential and field potential signals with high signal-to-noise ratio and temporal resolution from cultured neurons, cultured cardiomyocytes, acute brain slices and whole animal hearts. Measurements made with modulation-doped nanoscale active channel SiNW FETs demonstrate that signals recorded from cardiomyocytes are highly localized and have improved time resolution compared to larger planar detectors. In addition, several novel three-dimensional (3D) transistor probes, which were realized using advanced nanowire synthesis methods, have been implemented for intracellular recording. These novel probes include (i) flexible 3D kinked nanowire FETs, (ii) branched intracellular nanotube SiNW FETs, and (iii) active silicon nanotube FETs. Following phospholipid modification of the probes to mimic the cell membrane, the kinked nanowire, branched intracellular nanotube and active silicon nanotube FET probes recorded full-amplitude intracellular action potentials from spontaneously firing cardiomyocytes. Moreover, these probes demonstrated the capability of reversible, stable, and long-term intracellular recording, thus indicating the minimal invasiveness of the new nanoscale structures and suggesting biomimetic internalization via the phospholipid modification. Simultaneous, multi-site intracellular recording from both single cells and cell networks were also readily achieved by interfacing independently addressable nanoprobe devices with cells. Finally, electronic and biological systems have been seamlessly merged in 3D for the first time using macroporous nanoelectronic scaffolds that are analogous to synthetic tissue scaffold and the extracellular matrix in tissue. Free-standing 3D nanoelectronic scaffolds were cultured with neurons, cardiomyocytes and smooth muscle cells to yield electronically-innervated synthetic or ‘cyborg’ tissues. Measurements demonstrate that innervated tissues exhibit similar cell viability as with conventional tissue scaffolds, and importantly, demonstrate that the real-time response to drugs and pH changes can be mapped in 3D through the tissues. These results open up a new field of research, wherein nanoelectronics are merged with biological systems in 3D thereby providing broad opportunities, ranging from a nanoelectronic/tissue platform for real-time pharmacological screening in 3D to implantable ‘cyborg’ tissues enabling closed-loop monitoring and treatment of diseases. Furthermore, the capability of high density scale-up of the above extra- and intracellular nanoscopic probes for action potential recording provide important tools for large-scale high spatio-temporal resolution electrical neural activity mapping in both 2D and 3D, which promises to have a profound impact on many research areas, including the mapping of activity within the brain.Chemistry and Chemical BiologyEngineering and Applied Science

Solid State Circuits Technologies

The evolution of solid-state circuit technology has a long history within a relatively short period of time. This technology has lead to the modern information society that connects us and tools, a large market, and many types of products and applications. The solid-state circuit technology continuously evolves via breakthroughs and improvements every year. This book is devoted to review and present novel approaches for some of the main issues involved in this exciting and vigorous technology. The book is composed of 22 chapters, written by authors coming from 30 different institutions located in 12 different countries throughout the Americas, Asia and Europe. Thus, reflecting the wide international contribution to the book. The broad range of subjects presented in the book offers a general overview of the main issues in modern solid-state circuit technology. Furthermore, the book offers an in depth analysis on specific subjects for specialists. We believe the book is of great scientific and educational value for many readers. I am profoundly indebted to the support provided by all of those involved in the work. First and foremost I would like to acknowledge and thank the authors who worked hard and generously agreed to share their results and knowledge. Second I would like to express my gratitude to the Intech team that invited me to edit the book and give me their full support and a fruitful experience while working together to combine this book

Computational fluid dynamics modeling and in situ physics-based monitoring of aerosol jet printing toward functional assurance of additively-manufactured, flexible and hybrid electronics

Aerosol jet printing (AJP)—a direct-write, additive manufacturing technique—has emerged as the process of choice particularly for the fabrication of flexible and hybrid electronics. AJP has paved the way for high-resolution device fabrication with high placement accuracy, edge definition, and adhesion. In addition, AJP accommodates a broad range of ink viscosity, and allows for printing on non-planer surfaces. Despite the unique advantages and host of strategic applications, AJP is a highly unstable and complex process, prone to gradual drifts in machine behavior and deposited material. Hence, real-time monitoring and control of AJP process is a burgeoning need. In pursuit of this goal, the objectives of the work are, as follows: (i) In situ image acquisition from the traces/lines of printed electronic devices right after deposition. To realize this objective, the AJP experimental setup was instrumented with a high-resolution charge-coupled device (CCD) camera, mounted on a variable-magnification lens (in addition to the standard imaging system, already installed on the AJ printer). (ii) In situ image processing and quantification of the trace morphology. In this regard, several customized image processing algorithms were devised to quantify/extract various aspects of the trace morphology from online images. In addition, based on the concept of shape-from-shading (SfS), several other algorithms were introduced, allowing for not only reconstruction of the 3D profile of the AJ-printed electronic traces, but also quantification of 3D morphology traits, such as thickness, cross-sectional area, and surface roughness, among others. (iii) Development of a supervised multiple-input, single-output (MISO) machine learning model—based on sparse representation for classification (SRC)—with the aim to estimate the device functional properties (e.g., resistance) in near real-time with an accuracy of ≥ 90%. (iv) Forwarding a computational fluid dynamics (CFD) model to explain the underlying aerodynamic phenomena behind aerosol transport and deposition in AJP process, observed experimentally. Overall, this doctoral dissertation paves the way for: (i) implementation of physics-based real-time monitoring and control of AJP process toward conformal material deposition and device fabrication; and (ii) optimal design of direct-write components, such as nozzles, deposition heads, virtual impactors, atomizers, etc

VLSI Design

This book provides some recent advances in design nanometer VLSI chips. The selected topics try to present some open problems and challenges with important topics ranging from design tools, new post-silicon devices, GPU-based parallel computing, emerging 3D integration, and antenna design. The book consists of two parts, with chapters such as: VLSI design for multi-sensor smart systems on a chip, Three-dimensional integrated circuits design for thousand-core processors, Parallel symbolic analysis of large analog circuits on GPU platforms, Algorithms for CAD tools VLSI design, A multilevel memetic algorithm for large SAT-encoded problems, etc

Growth, modification and integration of carbon nanotubes into molecular electronics

Molecules are the smallest possible elements for electronic devices, with active elements for such devices typically a few Angstroms in footprint area. Owing to the possibility of producing ultrahigh density devices, tremendous effort has been invested in producing electronic junctions by using various types of molecules. The major issues for molecular electronics include (1) developing an effective scheme to connect molecules with the present micro- and nano-technology, (2) increasing the lifetime and stabilities of the devices, and (3) increasing their performance in comparison to the state-of-the-art devices. In this work, we attempt to use carbon nanotubes (CNTs) as the interconnecting nanoelectrodes between molecules and microelectrodes. The ultimate goal is to use two individual CNTs to sandwich molecules in a cross-bar configuration while having these CNTs connected with microelectrodes such that the junction displays the electronic character of the molecule chosen. We have successfully developed an effective scheme to connect molecules with CNTs, which is scalable to arrays of molecular electronic devices. To realize this far reaching goal, the following technical topics have been investigated. 1. Synthesis of multi-walled carbon nanotubes (MWCNTs) by thermal chemical vapor deposition (T-CVD) and plasma-enhanced chemical vapor deposition (PECVD) techniques (Chapter 3). We have evaluated the potential use of tubular and bamboo-like MWCNTs grown by T-CVD and PE-CVD in terms of their structural properties. 2. Horizontal dispersion of MWCNTs with and without surfactants, and the integration of MWCNTs to microelectrodes using deposition by dielectrophoresis (DEP) (Chapter 4). We have systematically studied the use of surfactant molecules to disperse and horizontally align MWCNTs on substrates. In addition, DEP is shown to produce impurityfree placement of MWCNTs, forming connections between microelectrodes. We demonstrate the deposition density is tunable by both AC field strength and AC field frequency. 3. Etching of MWCNTs for the impurity-free nanoelectrodes (Chapter 5). We show that the residual Ni catalyst on MWCNTs can be removed by acid etching; the tip removal and collapsing of tubes into pyramids enhances the stability of field emission from the tube arrays. The acid-etching process can be used to functionalize the MWCNTs, which was used to make our initial CNT-nanoelectrode glucose sensors. Finally, lessons learned trying to perform spectroscopic analysis of the functionalized MWCNTs were vital for designing our final devices. 4. Molecular junction design and electrochemical synthesis of biphenyl molecules on carbon microelectrodes for all-carbon molecular devices (Chapter 6). Utilizing the experience gained on the work done so far, our final device design is described. We demonstrate the capability of preparing patterned glassy carbon films to serve as the bottom electrode in the new geometry. However, the molecular switching behavior of biphenyl was not observed by scanning tunneling microscopy (STM), mercury drop or fabricated glassy carbon/biphenyl/MWCNT junctions. Either the density of these molecules is not optimum for effective integration of devices using MWCNTs as the nanoelectrodes, or an electroactive contaminant was reduced instead of the ionic biphenyl species. 5. Self-assembly of octadecanethiol (ODT) molecules on gold microelectrodes for functional molecular devices (Chapter 7). We have realized an effective scheme to produce Au/ODT/MWCNT junctions by spanning MWCNTs across ODT-functionalized microelectrodes. A percentage of the resulting junctions retain the expected character of an ODT monolayer. While the process is not yet optimized, our successful junctions show that molecular electronic devices can be fabricated using simple processes such as photolithography, self-assembled monolayers and dielectrophoresis

Growth and Electrical Properties of Chemical Vapour Deposited Low Dimensional sp2 Carbons.

This thesis describes the growth of sp2 carbon materials - namely graphene and carbon nanotube (CNT) materials using a chemical vapour deposition (CVD) process. A novel CVD process tool based on a photothermal process (PT-CVD) that differs from standard thermal CVD has been developed. This thesis reports the investigations into the properties of the deposited carbon nanomaterials and applications that exploit their electronic properties. The first investigation is into the growth of vertically aligned MWCNT forests. Growth of CNTs at 370°C by a one-step PT-CVD method was demonstrated. The growth rate can reach ~1.3 μm/min, which is faster than most other reported thermal CVD methods. The use of bimetallic catalyst (Fe/Ti) and the use of rapid thermal process are the keys to this process. AFM topography studies showed that the fast top-down heating mode of the PT-CVD leads to the formation of a Fe/Ti uniform solid solution, which is believed to improve the CNT growth. These CNTs are composed of a few layer crystalline graphene sheets with a 5-6 nm diameter. Raman scattering provides supporting evidence that the as-grown CNTs are of high quality, better than some CNTs grown at higher temperatures by traditional CVD methods. CVD growth of graphene was investigated using Cu foils as substrate, with the field-effect in the graphene subsequently demonstrated by transferring it to a back-gate bottom contact transistor arrangement using poly-4-vinyl-phenol gate dielectric as an alternative to oxide based insulators. This graphene transistor showed a simple, inexpensive fabrication method that is completely compatible to large scale fabrication of organic devices, to demonstrate a field effect hole mobility of 37 cm2/Vs. Despite the mobility being lower than that found in exfoliated graphene, it demonstrates the potential of a graphene based all carbon transistor for large area electronics. The fabrication and electrical performance of a 3 terminal graphene device is further reported. This device displayed characteristics similar to a p-type graphene FET. While past investigations of distortion and saturation in transfer characteristics of graphene FET indicated that metal-graphene interaction may be the controlling mechanism, this device operation is based on the design of transferring graphene onto a Diamond-like-carbon DLC/p-Si heterostructure with Si as the back contact and with the DLC acting as the dielectric support in contact to graphene. Thus, this provided a mechanism for the DLC/p-Si heterojunction to moderate the I-V characteristics of this device, resulting in a p-type only conduction process in graphene that is also saturable. Following the work on using conventional thermal CVD (T-CVD) for graphene growth, we demonstrated the possibility of using the PT-CVD to develop a graphene growth process. It is found that the non-thermal equilibrium nature of PT-CVD process resulted in a much shorter duration in both heating up and cooling down, thus allows the reduction of the overall growth time for graphene. The choice of performing growth on Ni also allows for the alleviation of hydrogen blister damage that is commonly encountered during growth on Cu substrates. To characterize the film’s electrical and optical properties, pristine PT-CVD grown graphene was used as the transparent electrode material in an organic photovoltaic devices (OPV) and is found to be comparable to that reported using pristine graphene prepared by conventional CVD

Research on flexible display at ulsan national institute of science and technology

Displays represent information visually, so they have become the fundamental building block to visualize the data of current electronics including smartphones. Recently, electronics have been advanced toward flexible and wearable electronics that can be bent, folded, or stretched while maintaining their performance under various deformations. Here, recent advances in research to demonstrate flexible and wearable displays are reviewed. We introduce these results by dividing them into several categories according to the components of the display: active-matrix backplane, touch screen panel, light sources, integrated circuit for fingerprint touch screen panel, and characterization tests; and we also present mechanical tests in nano-meter scale and visual ergonomics research

Carbon Nanomaterials and their application to Electrochemical Sensors: A review

Carbon has long been applied as an electrochemical sensing interface owing to its unique electrochemical properties. Moreover, recent advances in material design and synthesis, particularly nanomaterials, has produced robust electrochemical sensing systems that display superior analytical performance. Carbon nanotubes (CNTs) are one of the most extensively studied nanostructures because of their unique properties. In terms of electroanalysis, the ability of CNTs to augment the electrochemical reactivity of important biomolecules and promote electron transfer reactions of proteins is of particular interest. The remarkable sensitivity of CNTs to changes in surface conductivity due to the presence of adsorbates permits their application as highly sensitive nanoscale sensors. CNT-modified electrodes have also demonstrated their utility as anchors for biomolecules such as nucleic acids, and their ability to diminish surface fouling effects. Consequently, CNTs are highly attractive to researchers as a basis for many electrochemical sensors. Similarly, synthetic diamonds electrochemical properties, such as superior chemical inertness and biocompatibility, make it desirable both for (bio) chemical sensing and as the electrochemical interface for biological systems. This is highlighted by the recent development of multiple electrochemical diamond-based biosensors and bio interfaces