Search

A typical workflow for advanced package failure analysis usually focuses around two key sequential steps: defect localization and defect characterization. Defect localization can be achieved using a number of complementary techniques, but electro optical terahertz pulse reflectometry (EOTPR) has emerged as a powerful solution. This paper shows how the EOTPR approach can be extended to provide solutions for the growing complexity of advanced packages. First, it demonstrates how localization of defects can be performed in traces without an external connection, through the use of an innovative cross-sectional probing with EOTPR. Then, the paper shows that EOTPR simulation can be used to extract the interface resistance, granting an alternative way of quantitative defect characterization using EOTPR without the destructive physical analysis. These novel approaches showed the great potential of EOTPR in failure analysis and reliability analysis of advanced packaging.

X-ray imaging for both Failure Analysis and In-line Inspection has been utilized widely in the semiconductor industry, especially for surface mount device applications. During the investigation of total ionizing dose (TID) induced degradation of logic ICs with bulk FinFET technology, we observed that the degradation is mainly in the form of an increase in I/O leakage and IDDQ. Using filters during radiation was shown to impact TID. Failure Analysis was performed to localize the excessive current in both I/O leakage and IDDQ.

X-Ray imaging is widely used in the semiconductor industry, for failure analysis and for in-line inspection of surface mount devices. Here, we investigate the TID-induced degradation of logic ICs, which happens after long-term exposure to X-Ray. The observed degradation is mainly in the form of an increase in the leakage of input/output pins and the IDDQ of their circuitry. Annealing at high temperature is shown to partially recover the leakage degradation caused by the radiation.

We demonstrate that plasmonic response can be tuned spectrally via the alloy composition of an epitaxial semimetallic film. Specifically, attenuated total reflectance studies show that the surface plasmon resonance of rare-earth monopnictide LaxLu1–xAs alloy films can be tuned across the mid-IR, while lattice-matching to technologically important substrates. The electrical properties are a strong function of the composition, which, in turn, manifests as tunability of the optical properties. The ability to produce tunable (semi)metals that can be epitaxially integrated with III–V emitters and absorbers is expected to enable a new generation of novel nanophotonic device architectures and functionality.

Integration of a complementary metal-oxide semiconductor (CMOS) and monolayer graphene is a significant step toward realizing low-cost, low-power, heterogeneous nanoelectronic devices based on two-dimensional materials such as gas sensors capable of enabling future mobile sensor networks for the Internet of Things (IoT). But CMOS and post-CMOS process parameters such as temperature and material limits, and the low-power requirements of untethered sensors in general, pose considerable barriers to heterogeneous integration. We demonstrate the first monolithically integrated CMOS-monolayer graphene gas sensor, with a minimal number of post-CMOS processing steps, to realize a gas sensor platform that combines the superior gas sensitivity of monolayer graphene with the low power consumption and cost advantages of a silicon CMOS platform. Mature 0.18 µm CMOS technology provides the driving circuit for directly integrated graphene chemiresistive junctions in a radio frequency (RF) circuit platform. This work provides important advances in scalable and feasible RF gas sensors specifically, and toward monolithic heterogeneous graphene–CMOS integration generally. The combination of monolayer graphene with a silicon-based CMOS platform results in a monolithically integrated gas sensor. A team led by Deji Akinwande at the University of Texas at Austin developed a graphene-based gas sensing platform that leverages the remarkable gas sensitivity of graphene and the well-established advantages of silicon technology. Using a commercially available 0.18 μm CMOS radio-frequency (RF) circuit, the authors fabricated graphene chemi-resistive junctions atop the CMOS readout circuit, whereby the interaction between gas molecules and graphene can be read as an output frequency while minimizing the number of post-processing steps. The built-in RF functionalities enable a direct wireless connection with the transducer and offer reduced flicker noise, as opposed to direct-current sensors.

A convenient, one-pot three-component synthesis of new photochromic azo-imidazoles ( 1a - 1h ) from the corresponding azo dyes ( 2a - 2h) , benzil and ammonium acetate under microwave irradiation were described and their photochromic properties were investigated. The structures of the new azo-imidazoles were confirmed by UV–Vis, FT-IR and NMR spectroscopies and elemental analysis. The properties and photochromic structural behavior relationship (PSBR) of these compounds have been analyzed. All the compounds exhibit good photochromic behavior upon irradiation with alternative UV and visible light.

This paper tackles a common ground non-isolated bidirectional DC-DC converter for applications of micro-grids. The suggested converter consists of four main switches with their body diodes, three inductors, and four capacitors. Simple structure, vast voltage gain scope, low voltage tension in the switches and joint common ground among the input and the output are the merits of the suggested converter. Furthermore, the suggested converter provides high step-up/step-down voltage gain. Regarding the simplicity in this configuration, the control concept of the suggested converter is a straightforward conception. Doing so, this paper deals with steady-state analyses in both directions, voltage stress across the power switches, and a watchful survey in comparison between other bidirectional converters. Finally, the simulation results are concluded to validate the effectiveness of the analyses in the suggested converter.

We have achieved 140-nm channel length graphene thin-film transistors (TFTs) on flexible glass with a 95-GHz intrinsic cutoff frequency and greater than 30-GHz intrinsic power frequency after standard de-embedding. The flexible glass substrate offers subnanometer surface smoothness as well as high thermal conductivity, 1 W/ $\textrm {m}\,\cdot \, \textrm {K}$ , which can prevent thermomechanical failure, which is a limitation of plastic and rubber substrates. In addition, we developed a flexible 60-nm polyimide thin film as gate dielectric with low surface roughness less than 0.35 nm for optimal carrier transport and facilitate edge-injection contacts for low contact resistance. The maximum electron (hole) mobility is 4540 (1100) cm2/ $\textrm {V}\cdot \textrm {s}$ , and the extracted contact resistance in the electron (hole) branch is 1140 (720) $\Omega \cdot \mu \text{m}$ . The intrinsic cutoff frequency is 196% higher than our previous results on polymeric substrates. Importantly, the experimental saturation velocity of the graphene TFT is the highest for any flexible transistor on any material system reported so far.

Here we present a very fast, selective mechanical approach for transferring graphene with low levels of copper contamination from seed wafers on which it was grown to target wafers for very large scale integration (VLSI) electronics. We found that graphene/copper or copper/silicon oxide delamination paths could be selected by slow and faster separation rates, respectively. Thus graphene can be transferred to a target wafer, either exposed or protected by the seed copper layer, which can later be removed by etching. Delamination paths were identified by SEM and Raman spectroscopy. The sheet resistance of the graphene produced by the two approaches was slightly higher than graphene transferred by a PMMA wet-transfer process, indicating reduced impurity doping, and the variation in the sheet resistance values was much lower. Copper contamination levels, quantitatively established by TOF-SIMS, were several orders of magnitude lower than the values for PMMA assisted transfer. In addition, we demonstrated that top-gated transistor devices from our mechanical, delamination transferred graphene exhibited superior transistor behavior to PMMA-assisted wet transfer graphene. The adhesion energy, strength and range of the interactions were quantitatively determined by nonlinear fracture analyses, and suggest that the roughness of the interface between graphene and copper plays an important role with implications for improvements in manufacturing processes.

There is a growing interest in the design of novel flexible electronics for future internet of things (IoT) systems [1]. IoT requires design of low power RF electronics operating at GHz frequency range. Molybdenum disulphide (MoS2) is the prototypical transitional metal dichalcogenide (TMD) affording a large semiconducting bandgap (1.8eV), high saturation velocity, good mechanical strength, high mobility (> 50cm2/Vs), high on/off ratio (> 106), good current saturation and GHz RF performance [2]. In this work, we demonstrate wafer scale monolayer MoS 2 based flexible RF nanoelectronics that can be used for low power nanoelectronics and flexible IoT systems.

In summary, we report NPI as a flexible dielectric for transistors based on 2D atomic sheets such as graphene and MoS 2 , which features high mechanical flexibility, stable electrical performances and low roughness. NPI offers the realistic prospects for highly flexible electronics beyond the typical 2 % limitation of high-κ or ceramic gate dielectrics

We report the improvement of the electrical performance of field effect transistors (FETs) fabricated on monolayer chemical vapor deposited (CVD) MoS2, by applying an interacting fluoropolymer capping layer (Teflon-AF). The electrical characterizations of more than 60 FETs, after applying Teflon-AF cap, show significant improvement of the device properties and reduced device to device variation. The improvement includes: 50% reduction of the average gate hysteresis, 30% reduction of the subthreshold swing and about an order of magnitude increase of the current on-off ratio. These favorable changes in device performance are attributed to the reduced exposure of MoS2 channels to the adsorbates in the ambient which can be explained by the polar nature of Teflon-AF cap. A positive shift in the threshold voltage of all the measured FETs is observed, which translates to the more desirable enhancement mode transistor characteristics.