Contactless Test Access Mechanism for 3D IC

3D IC integration presents many advantages over the current 2D IC integration. It has the potential to reduce the power consumption and the physical size while supporting higher bandwidth and processing speed. Through Silicon Via’s (TSVs) are vertical interconnects between different layers of 3D ICs with a typical 5μm diameter and 50μm length. To test a 3D IC, an access mechanism is needed to apply test vectors to TSVs and observe their responses. However, TSVs are too small for access by current wafer probes and direct TSV probing may affect their physical integrity. In addition, the probe needles for direct TSV probing must be cleaned or replaced frequently. Contactless probing method resolves most of the TSV probing problems and can be employed for small-pitch TSVs. In this dissertation, contactless test access mechanisms for 3D IC have been explored using capacitive and inductive coupling techniques. Circuit models for capacitive and inductive communication links are extracted using 3D full-wave simulations and then circuit level simulations are carried out using Advanced Design System (ADS) design environment to verify the results. The effects of cross-talk and misalignment on the communication link have been investigated. A contactless TSV probing method using capacitive coupling is proposed and simulated. A prototype was fabricated using TSMC 65nm CMOS technology to verify the proposed method. The measurement results on the fabricated prototype show that this TSV probing scheme presents -55dB insertion loss at 1GHz frequency and maintains higher than 35dB signal-to-noise ratio within 5µm distance. A microscale contactless probe based on the principle of resonant inductive coupling has also been designed and simulated. Experimental measurements on a prototype fabricated in TSMC 65nm CMOS technology indicate that the data signal on the TSV can be reconstructed when the distance between the TSV and the probe remains less than 15µm

Wireless Testing of Integrated Circuits.

Integrated circuits (ICs) are usually tested during manufacture by means of automatic testing equipment (ATE) employing probe cards and needles that make repeated physical contact with the ICs under test. Such direct-contact probing is very costly and imposes limitations on the use of ATE. For example, the probe needles must be frequently cleaned or replaced, and some emerging technologies such as three-dimensional ICs cannot be probed at all. As an alternative to conventional probe-card testing, wireless testing has been proposed. It mitigates many of the foregoing problems by replacing probe needles and contact points with wireless communication circuits. However, wireless testing also raises new problems which are poorly understood such as: What is the most suitable wireless communication technique to employ, and how well does it work in practice? This dissertation addresses the design and implementation of circuits to support wireless testing of ICs. Various wireless testing methods are investigated and evaluated with respect to their practicality. The research focuses on near-field capacitive communication because of its efficiency over the very short ranges needed during IC manufacture. A new capacitive channel model including chip separation, cross-talk, and misalignment effects is proposed and validated using electro-magnetic simulation studies to provide the intuitions for efficient antenna and circuit design. We propose a compact clock and data recovery architecture to avoid a dedicated clock channel. An analytical model which predicts the DC-level fluctuation due to the capacitive channel is presented. Based on this model, feed-forward clock selection is designed to enhance performance. A method to select proper channel termination is discussed to maximize the channel efficiency for return-to-zero signaling. Two prototype ICs incorporating wireless testing systems were fabricated and tested with the proposed methods of testing digital circuits. Both successfully demonstrated gigahertz communication speeds with a bit-error rate less than 10^−11. A third prototype IC containing analog voltage measurement circuits was implemented to determine the feasibility of wirelessly testing analog circuits. The fabricated prototype achieved satisfactory voltage measurement with 1 mV resolution. Our work demonstrates the validity of the proposed models and the feasibility of near-field capacitive communication for wireless testing of ICs.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/93993/1/duelee_1.pd

Indirect contact probing method for characterizing vertical interconnects

Department of Electrical EngineeringRecently, vertical interconnects in wafer-level are used to achieve system integration with stacked chips. Although the wafer-level vertical interconnects provide smaller interconnection delay and lower power consumption, popularizing the technology is difficult due to testing issues. A main difficulty in testing vertical interconnects comes from that possible damages caused by the direct-contact probing. Therefore, an indirect contact probing method is presented for safe characterization in waver level. The proposed method is based on the capacitive coupling method. Utilizing a dielectric contactor, the sensitivity of capacitive coupling can be improved with ensuring the protection of vertical interconnects. In addition, extra probe control module and sensor electronics are not required since the dielectric contactor maintains the constant gap. The proposed method is verified in both cases of a single-pair via and multiple vias. The procedure of the proposed method for a single-pair vias starts with one-port calibration. To apply one-port calibration, we have measurements on three different calibration vias by the indirect and the direct-contact probing. From the measurement data, the characteristic of dielectric contactor is fully characterized. After the dielectric contactor is mounted on the DUT containing vertical interconnects, the DUT is measured by the indirect-contact probing manner. Finally, de-embedding the dielectric contactor portion, we can obtain the characteristic of a single-pair via. The proposed method is verified in printed circuit board (PCB) level. The extracted via impedances show a good agreement with the direct-contact probing in frequency ranges 0.8 GHz to 30 GHz and 2.5 GHz to 18 GHz by simulations and measurements, respectively. In the case of multi-via testing, the procedure is similar to a single-pair via extraction but additional fixtures are required. By adopting the socket and calibration substrates, the dielectric contactor consisting of multiple pads can be characterized. From dielectric contactor characteristics corresponding to each via, multiple vias can be extracted based on the reference plane. The extracted impedances of multiple vias show a good agreement with the direct-contact probing up to 24 GHz by simulations and 22 GHz by measurements. From the extracted impedances, we can diagnose all defects among multiple vias. Since the proposed method for multi-via test is limited to testing, the indirect contact probing method for the multi-port characterization is also proposed. It characterizes a multi-port network of a DUT by de-embedding the multi-port characteristics of the dielectric contactor, hence we can also capture inter-via couplings from a multi-port network. Based on simulations, a two-port network is successfully characterized in the range of 0.8 GHz to 24 GHz.ope

Planar-Goubau-line components for terahertz applications

Terahertz-wave technology has a broad range of applications, including radio astronomy, telecommunications, security, medical applications, pharmaceutical quality control, and biological sensing. However, the sources, detectors, and components are less efficient at this frequency band due to parasitic effects and increased total losses, which hinder the performance of terahertz systems. A common platform for terahertz systems is planar technology, which offers good integration, ease of fabrication, and low cost. However, it also suffers from high losses, which must be minimised to keep the system\u27s performance. A pivotal choice to reduce losses is using power-efficient waveguides, and single-conductor waveguides have shown promisingly high power efficiencies compared to multi-conductor planar waveguides. The planar Goubau line (PGL) is a planar single-conductor waveguide consisting of a metal strip on top of a dielectric substrate which propagates a quasi-transverse magnetic surface wave, similarly to Sommerfeld\u27s wire and the Goubau line, a conducting wire coated with a dielectric layer. Some limitations of the PGL, which complicate the design of components, are the lack of a ground plane and the weak dependence of impedance with the metal strip width of the line.This thesis presents the development of PGL technology and components for terahertz frequencies. It developed design strategies to maximise the power efficiency, using electrically-thin substrates, which drastically drop radiation losses compared to thick substrates. The first PGL calibration standards were developed, which de-embeds the transition needed to excite the propagation mode and sets the calibration plane along the line, allowing the direct characterisation of PGL components. This work also presents several PGL components with a straightforward design procedure, including a stopband filter based on capacitively-coupled λ/2 resonators, an impedance-matched load based on an exponentially-tapered corrugated line, and a power divider based on capacitive-gap coupled lines to a standing wave in the input port. Finally, the PGL was integrated with a microfluidic channel to measure changes in the complex refractive index of a high-loss aqueous sample (water/isopropyl alcohol) as the first step toward a biological sensor

Field-Effect Sensors

This Special Issue focuses on fundamental and applied research on different types of field-effect chemical sensors and biosensors. The topics include device concepts for field-effect sensors, their modeling, and theory as well as fabrication strategies. Field-effect sensors for biomedical analysis, food control, environmental monitoring, and the recording of neuronal and cell-based signals are discussed, among other factors

QUBIT COUPLED MECHANICAL RESONATOR IN AN ELECTROMECHANICAL SYSTEM

This thesis describes the development of a hybrid quantum electromechanical system. In this system the mechanical resonator is capacitively coupled to a superconducting transmon which is embedded in a superconducting coplanar waveguide (CPW) cavity. The difficulty of achieving high quality of superconducting qubit in a high-quality voltage-biased cavity is overcome by integrating a superconducting reflective T-filter to the cavity. Further spectroscopic and pulsed measurements of the hybrid system demonstrate interactions between the ultra-high frequency mechanical resonator and transmon qubit. The noise of mechanical resonator close to ground state is measured by looking at the spectroscopy of the transmon. At last, fabrication and tests of membrane resonators are discussed

Integrated Nanoscale Tools for Interrogating Living Cells

The development of next-generation, nanoscale technologies that interface biological systems will pave the way towards new understanding of such complex systems. Nanowires – one-dimensional nanoscale structures – have shown unique potential as an ideal physical interface to biological systems. Herein, we focus on the development of nanowire-based devices that can enable a wide variety of biological studies. First, we built upon standard nanofabrication techniques to optimize nanowire devices, resulting in perfectly ordered arrays of both opaque (Silicon) and transparent (Silicon dioxide) nanowires with user defined structural profile, densities, and overall patterns, as well as high sample consistency and large scale production. The high-precision and well-controlled fabrication method in conjunction with additional technologies laid the foundation for the generation of highly specialized platforms for imaging, electrochemical interrogation, and molecular biology. Next, we utilized nanowires as the fundamental structure in the development of integrated nanoelectronic platforms to directly interrogate the electrical activity of biological systems. Initially, we generated a scalable intracellular electrode platform based on vertical nanowires that allows for parallel electrical interfacing to multiple mammalian neurons. Our prototype device consisted of 16 individually addressable stimulation/recording sites, each containing an array of 9 electrically active silicon nanowires. We showed that these vertical nanowire electrode arrays could intracellularly record and stimulate neuronal activity in dissociated cultures of rat cortical neurons similar to patch clamp electrodes. In addition, we used our intracellular electrode platform to measure multiple individual synaptic connections, which enables the reconstruction of the functional connectivity maps of neuronal circuits. In order to expand and improve the capability of this functional prototype device we designed and fabricated a new hybrid chip that combines a front-side nanowire-based interface for neuronal recording with backside complementary metal oxide semiconductor (CMOS) circuits for on-chip multiplexing, voltage control for stimulation, signal amplification, and signal processing. Individual chips contain 1024 stimulation/recording sites enabling large-scale interfacing of neuronal networks with single cell resolution. Through electrical and electrochemical characterization of the devices, we demonstrated their enhanced functionality at a massively parallel scale. In our initial cell experiments, we achieved intracellular stimulations and recordings of changes in the membrane potential in a variety of cells including: HEK293T, cardiomyocytes, and rat cortical neurons. This demonstrated the device capability for single-cell-resolution recording/stimulation which when extended to a large number of neurons in a massively parallel fashion will enable the functional mapping of a complex neuronal network.Physic

The rise of flexible electronics in neuroscience, from materials selection to in vitro and in vivo applications

Neuroscience deals with one of the most complicate system we can study: the brain. The huge amount of connections among the cells and the different phenomena occurring at different scale give rise to a continuous flow of data that have to be collected, analyzed and interpreted. Neuroscientists try to interrogate this complexity to find basic principles underlying brain electrochemical signalling and human/animal behaviour to disclose the mechanisms that trigger neurodegenerative diseases and to understand how restoring damaged brain circuits. The main tool to perform these tasks is a neural interface, a system able to interact with brain tissue at different levels to provide a uni/bidirectional communication path. Recently, breakthroughs coming from various disciplines have been combined to enforce features and potentialities of neural interfaces. Among the different findings, flexible electronics is playing a pivotal role in revolutionizing neural interfaces. In this work, we review the most recent advances in the fabrication of neural interfaces based on flexible electronics. We define challenges and issues to be solved for the application of such platforms and we discuss the different parts of the system regarding improvements in materials selection and breakthrough in applications both for in vitro and in vivo tests