Chip Substrate Research Articles

Two optofluidic devices for the refractive index measurement of small volume of fluids

Two simple optofluidic devices based on a microprism and a refraction channel, respectively, are proposed for measuring the refractive index of fluids. The microprism chip consists of an optical waveguide channel and a single triangular chamber filled with the test fluid, while the refraction channel chip consists of a single turning channel which functions as a liquid-core/solid-cladding optical waveguide. In both chips, the refractive index of the test fluid is calculated from a CCD image of the refracted ray in accordance with simple geometrical optics principles. The experimental results show that the refraction channel chip provides a more accurate measurement performance than the microprism chip; particularly for colloidal samples. However, the refraction channel chip is suitable only for the measurement of fluids with a refractive index greater than that of the chip substrate. Overall, the results presented in this study show that both devices provide a simple, low cost and effective means of determining the refractive index of a wide range of common test fluids with nano-liter volume.

Modeling and Understanding of External Latchup in CMOS Technologies—Part II: Minority Carrier Collection Efficiency

The n-wells of the parasitic p-n-p-n devices found in a CMOS layout will collect excess minority carriers from the chip substrate, potentially triggering latchup. This paper presents a model for the minority carrier collection efficiency of a given substrate current injector and collector pair; the model captures the effects of spacing, supply voltage, temperature, and current level. The model further describes the quantitative reduction in collection efficiency obtained by using guard rings. A good fit of the model to measurement results is observed in four different CMOS technologies.

Ube2w and Ataxin-3 Coordinately Regulate the Ubiquitin Ligase CHIP

The mechanisms by which ubiquitin ligases are regulated remain poorly understood. Here we describe a series of molecular events that coordinately regulate CHIP, a neuroprotective E3 implicated in protein quality control. Through their opposing activities, the initiator E2, Ube2w, and the specialized deubiquitinating enzyme (DUB), ataxin-3, participate in initiating, regulating, and terminating the CHIP ubiquitination cycle. Monoubiquitination of CHIP by Ube2w stabilizes the interaction between CHIP and ataxin-3, which through its DUB activity limits the length of chains attached to CHIP substrates. Upon completion of substrate ubiquitination, ataxin-3 deubiquitinates CHIP, effectively terminating the reaction. Our results suggest that functional pairing of E3s with ataxin-3 orsimilar DUBs represents an important point of regulation in ubiquitin-dependent protein quality control. Inaddition, the results shed light on disease pathogenesis in SCA3, a neurodegenerative disorder caused by polyglutamine expansion in ataxin-3.

Characterization of the adhesion of thin film by Cross-Sectional Nanoindentation: Analysis of the substrate edge chipping and the film delamination

Cross-Sectional Nanoindentation (CSN) is a recent method for adhesion measurement of nanoscale thin films in Ultra-Large Scale Integrated circuits. In the case of ductile thin films, the motion of the substrate chip implies significant plastic deformation of the film and complex geometry of delaminated areas. This article recalls first the experimental procedure and the two main features observed in this test performed on various plane copper films deposited on silicon: the critical force producing silicon edge chipping increases linearly with the distance of the indenter to the interface; on the section the delaminated length of the film ( a − b ) is proportional to the residual silicon chip displacement u f and the ratio S = u f / ( a − b ) depends on the manufacturing process of the film, and is so related to its adhesion to the substrate. One proposes a simple analysis of the silicon edge chipping. Then a model of pull-off of an elastic-strain hardening plastic film is developed, which suggests an explanation for the delamination process. Application of the model to experimental results starting from films plastic properties deduced from nanoindentation measurements provides plausible results. Some improvements for performing the CSN test are proposed in order to make easier its interpretation.

A new bubble-driven pulse pressure actuator for micromixing enhancement

We demonstrate a thermal bubble-driven loop actuator for microfluidic applications. The working principle is similar to that of human being's heart. The actuator consists of a diverging section and a circular chamber. A slim microheater was deposited on the back surface of the glass cover, facing the diverging section of the bottom substrate. The Marangoni effect switches the states of a “long” bubble during the pulse duration stage and a sphere or a circular bubble during the pulse off stage, exporting the pulse pressure and yielding a large convection heat transfer at the vapor–liquid interface. Besides, the loop configuration pumps the bulk fluid movement around the loop. The above features protect the microheater from burnout and dissipate the Joule heat generated by the pulse heating to the supporting structure of the chip substrate, keeping the chip at the room temperature level. The newly designed loop actuator can be integrated with microfluidic systems. The loop actuator has no moving parts thus it has high reliability. Because the thermal bubble never comes out of the loop actuator, the actuator is attractive for biology applications. We demonstrate the loop actuator used for mixing enhancement. The low pulse frequency such as 10 Hz yields a wavy mixing interface, but the high pulse frequencies result in a set of mixing clouds in the mixing channel. The mixing degrees are increased with increases in pulse frequencies. The fluid samples are uniformly distributed across the channel width direction for the pulse frequency of 100 Hz. The mixing degree can reach 0.94 for a short mixing length of about a couple of millimeter at the pulse frequency of 100 Hz. The fluid Reynolds number does not influence the mixing degrees in the mixing channel.

Multi-Order Dynamic Range DNA Sensor Using a Gold Decorated SWCNT Random Network

A novel electrical DNA biosensor is presented, which consists of gold (Au) nanoscale islands and a single-walled carbon nanotube (SWCNT) network on top of a concentric Au electrode array (also referred to as the CGi). The decorated Au islands on the SWCNT network provide ideal docking sites for ss-DNA probe (p-DNA) molecules. They also provide better adhesion between the SWCNT network and the chip substrate. In addition, the concentric electrode gives asymmetric current voltage characteristics in the solution and provides more flexible bias options to the electrodes. The sensor system is applied to a DNA sensor after functionalization with a 25 mer p-DNA (5'-HSC(6)-C(18)-GCCATTCTCACCGGATTCAGTCGTC-3'), hereafter called the [CGi+p-DNA]. The response of the DNA sensor has been measured in both real-time during hybridization with the complementary target ss-DNAs (t-DNA) and the static mode after the hybridization and washing steps. A wide dynamic range from the 100 fM to 1 μM has been achieved from the real-time mode and the static mode. Moreover, it is shown that the sensor system differentiates partially mismatched (single nucleotide polymorphism (SNP), half mismatch, noncomplementary) t-DNA, as well. The [CGi] sensor platform can be easily extended to target specific biological recognition elements such as aptamers or proteins.

Light-driven manipulation of picobubbles on a titanium oxide phthalocyanine-based optoelectronic chip

Microbubbles have a variety of applications in science and biological technology. Here, we demonstrate the manipulation of the picoliter gas bubble (picobubble) based on the optoelectronic-mechanism. The organic photoconductive material, titanium oxide phthalocyanine (TiOPc), was developed to make the light-sensitive substrate of this optoelectronic chip. The virtual electrodes are formed by projecting the dynamic light pattern onto TiOPc layer for generating the desired nonuniform electric field. The picobubble suspended in silicone oil can be manipulated with the velocity of 40–50 μm/s. The driving force up to 160 pico-Newtons could be generated for manipulating a gas bubble of 300 picoliters.

Lab-on-a-chip technologies for massive parallel data generation in the life sciences: A review

Lab-on-a-chip (LOC) technology is an important and rapidly developing research field focused on improving experimentation and analysis in the life sciences through miniaturization of full analytical systems into (monolithic) chip substrates. Since its emergence in the 1970s [1], the field has matured, gaining tremendous momentum in the last two decades. Miniaturization and integration of analytical processes on a chip can offer enormous advantages over existing technologies and can create a range of novel opportunities in the life sciences. The developments in the field have led to significant increases in analysis throughput, more than billion-fold sample volume reductions and increased separation efficiency. Despite its potential for the life sciences, the existence and the implications of LOCs are not widely known outside its community. The aim of this review is to introduce scientists from different disciplines to LOC technology. We will discuss the most important LOCs, their physical operating principles and the unique benefits that can be gained through miniaturization. We will conclude this review with a discussion of the potential of LOCs for massive parallel data generation and their potential implications for the life sciences.

A New Contactless Assembly Method for Paper Substrate Antennas and UHF RFID Chips

This paper deals with a low-cost method for the assembly of flexible substrate antennas and UHF RF identification silicon (Si) chips. Such a method exploits a magnetic coupling mechanism, thus not requiring for galvanic contacts between the Si chip and antenna itself. The magnetic coupling is established by a planar transformer, the primary and secondary windings of which are implemented on flexible substrate and Si chip, respectively. As a result, the Si chip can be assembled on the antenna with a mere placing and gluing process. First, the idea has been validated by theory. Electromagnetic simulations of a square heterogeneous transformer (1.0-mm side) show a maximum available power gain (MAG) of -0.4 dB at 868 MHz. In addition, the heterogeneous transformer is also quite tolerant with respect to misalignment between primary and secondary. An offset error of 150 μm reduces the MAG to - 0.5 dB. A sub-optimal matching strategy, exploiting a simple on-chip capacitor, is then developed for antennas with 50- Ω input impedances. Finally, the idea has been experimentally validated exploiting printed circuit board (PCB) prototypes. A PCB transformer (1.5-mm side) and a transformer rectifier (two-diode Dickson multiplier) have been fabricated and tested. Measurements indicates a MAG of -0.3 dB at 868 MHz for the transformer and the capability of the developed rectifier to supply a 220-kΩ load at 1.5 V with a - 2-dBm input power.

Basic study on nanofabrication of biodegradable plastics applying biochemical machining

Plastics are regarded as proper materials for microfluidic chips, and, in particular, biodegradable plastics will be more appropriate from the viewpoint of environmental friendliness. In addition, when they are utilized as chip substrate, biochemical machining can be applied. Biochemical machining is a process, which utilizes enzymatic biodegradation. This paper describes studies on application of biochemical machining to nanofabrication of poly( l -lactic acid) (PLLA), which is one of the most widely used biodegradable plastics industrially. The degradation performance of enzyme (proteinase K) was experimentally evaluated to extrapolate a suitable condition for nanofabrication. Additionally, in order to make arbitrary channels with nano-order depth on PLLA, mask fabrication was proposed. It is a fabrication method to control degraded regions and obtain desired shapes with a mask, which has penetrating grooves. Using this method, we achieved fabrication of straight grooves with nano-scale depth. In conclusion, it is clear that biochemical machining can realize an effective process of arbitrarily shaped nanogrooves on PLLA.

Embedded Actives and Its Industry Effects

Over the 60 plus year history of microelectronics packaging, electronic devices have been mounted onto an interconnect structure to form a microelectronics circuit. The devices could be bare chips, CSPs or packaged components such as SMT or thru-hole carriers. The interconnect structures could be circuit boards, ceramic substrates or flex circuits. This methodology has enabled a clear divide between the fabrication, assembly and test of the semiconductor device, the fabrication and test of the interconnect structure and the assembly and test of the component/substrate assembly. Over the past decade a new packaging methodology, embedded actives (chips), has been developed that changes all of these industry norms. In an embedded actives packaging approach, one or more bare or chip scale semiconductor devices are embedded within the interconnect structure. Although these approaches have significant electrical performance, size and cost benefits, the normal barriers between chip packaging, substrate fabrication and component assembly are removed. The interconnect structure is not completed prior to component embedding and the embedded component cannot be tested at packaged part level without the interconnect structure. This complicates electrical testing and makes it virtually impossible to differentiate between a defective component, a defective interconnect or a defective component to substrate contact. This paper will look at the history of embedded active developments and go into the various processes and structures being used. It will cover their electrical, reliability and size advantages and will address the revolutionary changes that the microelectronics industry must make to effectively utilize these technologies.

Novel Wet Chemical Copper Metallization for Glass Interposers

The focus of the chip and IC substrate manufacturing industry for interposers is currently shifting from organic substrates to inorganic materials. Interposers overcome the dimensional mismatch between a die and an organic PWB substrate and need to buffer the differences in thermal expansion between these two materials. While inorganics like silicon and glass, have a low CTE value compared to organic material, glass has some significant advantages over silicon. These are namely material cost, availability in panel size and a better electrical insulation. In order to further increase the cost advantage, metallization could be done by either electroless or electrolytic copper plating as an alternative route to sputter technology. Both wet chemical processes are well established in PWB manufacturing and need adaptation to glass substrates. Compared to sputtering, 3D-features can be covered with a wet chemical treatment in a comparatively economical process. Filling of TGVs (Through Glass Vias) by electrolytic copper plating requires the presence of a conductive film which is created by applying electroless copper deposition of typically 300–500nm thickness. The general issue is poor adhesion to the smooth glass surfaces. To improve adhesion between glass and metal, various treatments were assessed in this study: Mechanical anchoring was achieved by etching the substrate (subtractive) as well as by depositing nano-sized silica particles (additive). Both treatments are in solution and 3D-features are accessible in contrast to a purely mechanical approach. Surface treatments without inducing additional roughness included the adsorption of functional metal-affine polyelectrolytes and silanization for conditioning which enhanced the adhesion of the copper layer to various degrees. To study the impact of chemical formulation on strain/stress development and relaxation in the film as a key impact factor for blister (adhesion) performance, the electroless copper layer growth was monitored by in-situ XRD methods during and after deposition.

Single on-chip gold nanowires for electrochemical biosensing of glucose

The development of glucose diagnostic devices with low detection limits is of key importance in diabetes-related research. New highly sensitive sensors are required for non-invasive detection of glucose in bodily fluids, other than blood, and an electrochemical sensor based on a single gold nanowire for rapid, reliable and quantitative detection of low glucose concentrations (10 μM-1 mM), is presented in this paper. Single gold nanowire devices are fabricated at silicon chip substrates using a hybrid electron beam-photolithography approach. Critical dimensions of the nanowires are characterised using a combination of scanning electron and atomic force microscopies. Fabricated nanowire devices are characterised by direct electrical probing and cyclic voltammetry to explore functionality. The voltammetric detection of glucose was performed using ferrocene monocarboxylic acid as an oxidising mediator in the presence of glucose oxidase. The biosensor can be applied to the quantification of glucose in the range of 10 μM-100 mM, with an extremely high sensitivity of 7.2 mA mM(-1) cm(-2) and a low detection limit of 3 μM (S/N = 3). The sensor demonstrated high selectivity towards glucose with negligible interference from other oxidizable species including uric acid, ascorbic acid, mannose, fructose, salicylic acid (Aspirin) and acetaminophen (Paracetamol).

Oligonucleotide immobilization using 10-(carbomethoxy)decyl-dimethylchlorosilane for mRNA isolation and cDNA synthesis on a microfluidic chip

Fabrication of microfluidic systems capable of extracting and isolating nucleic acids from biological samples and preparing them for downstream applications within the same device is of interest as on-chip sample preparation reduces the time and effort expended on multi-step benchtop procedures. A microfluidic chip capable of cell lysis, nucleic acid extraction and immobilization has been developed in our laboratory. This report focuses on substrate development and chip integration of the nucleic acid immobilization platform. The immobilization region was initially developed using poly-adenylated mRNA released from normal human lymphoblastoid cells. After immobilization, the mRNA remains functional for amplification by the reverse transcription polymerase chain reaction (RT-PCR) and quantitative real-time PCR (qPCR) gene expression analyses. Detailed surface functionalization, chemical modification, and covalent oligonucleotide immobilization methods are described. Vapor and liquid deposition techniques for Pyrex functionalization by 10-(carbomethoxy)decyl-dimethylchlorosilane (CMDCS) were developed and an optimal method was determined for microfluidic chip application. CMDCS substrate depositions and modification were characterized by atomic force microscopy and contact angle goniometry, respectively. Oligonucleotide immobilizations and mRNA bindings were determined by fluorescence microscopy. Functional, selective platform integration within the microfluidic chip was confirmed by standard RT-PCR and qPCR systems.

Development of Cell Chip Based on Track Detector for Examination of Biological Damage by Alpha Particles

A cell chip was developed for the examination of biological damage of cells irradiated by high-energy alpha particles. A CR-39 track detector was employed as a chip substrate to identify high-energy charged particles traversing target cells. Moreover, the patterning of a photopolymer layer spatially controlled the cellular adhesiveness on the chip substrate. HeLa cancer cells were cultured on a micropatterned photopolymer layer. In this way, all the cells on the chip were individually addressed through the block number in the photopolymer pattern. The biocompatibility of the cell chip was examined through a viability test with fluophor reagent and measurement of the cell proliferation rate. HeLa cancer cells on the chip were irradiated with alpha particles and stained with a fluorescent probe molecule for DNA damage detection. The CR-39 substrate was etched by means of an alkali solution during cell incubation. The HeLa cells and alpha tracks were successfully observed by microscopy at once. It was confirmed that fluorescent spots corresponding to DNA damage were located in the direction of the major axis of oval alpha tracks.

Thermal measurements and analysis of AlGaInP/GaInP MQW red LEDs with different chip sizes and substrate thicknesses

Thermal properties of AlGaInP/GaInP MQW red LEDs are investigated by thermal measurements and analysis for different chip sizes and substrate thicknesses. To extract the thermal resistance (Rth), junction temperature (Tj) is experimentally determined by both forward voltage and electroluminescence (EL) emission peak shift methods. For theoretical thermal analysis, thermal parameters are calculated in simulation using measured heat source densities. The Tj value increases with increasing the injection current, and it decreases as the chip size becomes larger. The use of a thin substrate improves the heat removal capability. At 450mA, the Tj values of 315K and 342K are measured for 500×500μm2 LEDs with 110μm and 350μm thick substrates, respectively. For 500×500μm2 LEDs with 110μm thick substrate, the Rth values of 13.99K/W and 14.89K/W are obtained experimentally by the forward voltage and EL emission peak shift methods, respectively. The theoretically calculated value is 13.44K/W, indicating a good agreement with the experimental results.

In-Plane Parallel Scanning: A Microarray Technology for Point-of-Care Testing

A new microarray technology is described for rapid, inexpensive, multiplex diagnostics assays. Referred to as "in-plane parallel scanning" (IPPS), this technology replaces expensive laser scanning with a grid of 100-μm-wide waveguides embedded in the chip's substrate, enabling real-time quantification of molecular complex formation on the chip's surface. Compared to conventional microarray technology, IPPS has advantages of shorter assay time and lower instrument cost and complexity so that the platform can potentially be used in point-of-care (POC) settings. Two different chip formats are described: a low-density microarray with 10 sensing wells (IPPS-10) and a medium-density one with 100 sensing wells (IPPS-100). Performance was evaluated in two different proof-of-principle immunoassays: interleukin-1β (IL-1β) and Clostridium difficile toxin A. The two assays gave similar limits of detection of 0.67 and 0.94 pM, respectively. A saturation kinetics model described the sensor response with apparent dissociation constants of 511 pM for IL-1β and 6.47 nM for C. difficile toxin A toxoid. The multiplexing capabilities of the IPPS technology were also demonstrated in a multiplex assay for both analytes on the same IPPS-10 chip. Based on these results, the IPPS technology holds promise for translating diagnostic microarrays into near-patient environments.

Numerical Analysis for Thermal Performance of High Power Multi-Chip LED Packaging

Heat dissipation and cost are the key issues for light-emitting diode (LED) packaging. In this paper, based on the thermal resistance network model of LED packaging, three-dimensional heat dissipation model of high power multi-chip LED packaging is developed and analyzed with the application of finite element method. Temperature distributions of the current multi-chip LED packaging model are investigated systematically under the different materials of the chip substrate, die attach, and/or different structures of the heat sink and fin. The results show that the junction temperature can be decreased effectively by increasing the height of the heat sink, the width of the fin, and the thermal conductivity of the chip substrate and die attach materials. The lower cost and higher reliability for LED source can be obtained through reasonable selection of materials and structure parameters of the LED lighting system.

Integrated Carbon Nanotubes Electrodes in Microfluidic Chip via MWPCVD

An on-chip electrochemical detector for microfluidic chips was described, based on integrated carbon nanotube (CNT) electrodes directly onto the chip substrate through microwave plasma chemical vapor deposition (MWPCVD). The attractive performance of the integrated CNT electrodes was demonstrated for the amperometric detection of sucrose, glucose and D-fructose. The integrated CNT electrodes showed stronger electrocatalytic activity than gold electrodes.

Ultra-Wideband Chip Attenuator for Precise Noise Measurements at Cryogenic Temperatures

A 20-dB chip attenuator designed for cryogenic noise measurements from dc up to 40 GHz is presented. The chip is based on the use of temperature-stable tantalum-nitride thin-film resistors, a high thermal conductivity substrate such as crystal quartz (z-cut), and a suitable design that avoids inner conductor thermal heating, which is an important limiting factor for the precision of cryogenic noise measurements. A high-accuracy temperature sensor installed inside the attenuator module provides precise temperature characterization close to the chip location. The high thermal conductivity of the chip substrate in the designed attenuator assures a negligible temperature gradient between the resistive elements in the chip and the sensor, thus improving the measurement accuracy. The attenuator also shows an excellent electrical performance with insertion losses of 19.9 dB ± 0.65 dB and return losses better than 20.6 dB in the whole frequency range at 296 K. The insertion loss change when cooled to 15 K is less than 0.25 dB, which demonstrates its temperature stability.