Smaller Feature Sizes Research Articles

Analysis and Control of the Permanent Magnet Synchronous Motor With Auxiliary Modular Design

U-shape core permanent magnet synchronous motor (PMSM) has the features of small size, simple and robust construction, generally working in the low power and low cost industry applications [1], [2]. Due to the simple structure and the self-starting ability, single-phase PMSM with U-shape core got more attentions in early research and application, however, its development was limited by motor large torque ripple and low efficiency. As one effective way to solve the problem, the PMSM with auxiliary modular design comes out [2], which can obtain a smooth operation feature with shifted magnets array and supply the opportunity for fault tolerant control. Based on the two-phase PMSM with auxiliary modular design, the motor mathematical model and the fault tolerant control configuration are presented in this paper to illustrate motor characteristics and achieve the fault-tolerant ability. Finally, the motor prototype is tested and the experimental results are used to verify the proposed steady operation and the fault-tolerant strategy.

Extinction Capability of Carbon Nanofibers to Millimeter Wave

Carbon nanofibers, whose diameter is between carbon nanotubes and conventional carbon fibers, is a new type of nanomaterials with features of good absorbing performance, small size and low density, and is easy to meet the requirements of passive interference materials.To study the interference properties of carbon nanofibers to millimeter wave, the interaction model of carbon nanofibers and electromagnetic field is established in this paper. The integral equation of the carbon nanofibers inductive current is established and solved by using of the method of moment, and the formula of mass extinction coefficient is obtained. The relationships between the mass extinction coefficient of carbon nanofibers and the millimeter wavelength, the diameter and length of fibers are analyzed via programming by Matlab. It is revealed that the extinction capability of carbon nanofibers decreases as the wavelength of millimeter wave increases. The larger the ratio of length to diameter of carbon nanofibers, the better its extinction capability to millimeter wave will be.

A Rectangular Loop Yagi–Uda Antenna by the Two Materials 3-D Printing Technology

We present a rectangular loop Yagi–Uda antenna based on the three-dimensional (3-D) printing technology. The antenna comprises a ground plane, a rectangular loop driven element, and rectangular loop directors. The loop driven element is about λ0/20 above the ground plane and is fed by a 50 Ω microstrip feedline. We fabricated the Yagi–Uda antenna by two materials 3-D printing technology and the following chemical plating process. The measured results show the antenna's working frequency is at 2.392 GHz while the |S 11|, gain, and efficiency are –12.63 dB, 8.99 dBi, and 79.5%, respectively. The experimental results are in a good agreement with the design. Our loop Yagi–Uda antenna features good antenna performances, small size, and easy fabrication, which can be an excellent candidate for antenna arrays and applications that need directional radiation property. Our work paves the way to the application of 3-D printing technology in the field of antennas.

Performance of a Semi-Analytical Dose Engine Designed for Spot Scanning Proton Therapy with Small Spot Sizes

To study the clinical performance of a semi-analytical dose engine developed for spot scanning proton delivery systems that feature small spot sizes. The dose engine used a ray-tracing pencil beam algorithm with three lateral Gaussian components. It was commissioned using Monte Carlo (MC) data generated by an experimentally well-benchmarked Geant4 code and then fine-tuned using point dose measurements with various combinations of energy layers, field sizes, depths, and SOBPs. The dose engine used water-equivalent distance in both the beam direction and the lateral direction to account for inhomogeneity. Ten patients representing different disease sites were randomly selected for validation. Comparisons were done in water with data calculated from a fast MC code and with ionization chamber array measurements for patient-specific QA (including point doses, dose profiles, 2D-3D, and 3D-3D gamma analysis) and in patient geometries with MC data (including dose volume histogram indices and 3D-3D gamma analysis). In-water gamma passing rates using 3%/3mm criteria for these ten patients were greater than 97% when compared to MC and greater than 95% when compared to dose plane measurements. Excellent agreement was observed for dose profiles and point dose measurements in water. Good agreement between the semi-analytical engine and the MC code was also observed in patient geometries. This dose engine has been successfully used at our institution as a fast, independent second check for over two years. A ray-tracing dose engine with three lateral Gaussian components can accurately calculate dose distributions for our proton delivery system.Abstract 1167; TableExample treatment plan DVH indicesMonte CarloDose engineCTV statisticsMean dose [cGy(RBE)]5228.65229.1D95% [cGy(RBE)]4943.45006.6Head and NeckBrain D1% [cGy(RBE)]4336.34330.6OARsBrain stem D1% [cGy(RBE)]3906.94062.2Spinal cord D1% [cGy(RBE)]2684.32728.5Eye mean dose (L/R) [cGy(RBE)]1362.7 / 1947.21389.7 / 1890.1 Open table in a new tab

Real-time distributed monitoring of pressure and shock velocity by ultrafast spectrometry with Chirped Fiber Bragg Gratings: Experimental vs calculated wavelength-to-pressure sensitivities in the range [0–4 GPa

Fiber Bragg Gratings (FBGs) are gaining acceptance as velocity/pressure gauges in the fields of detonation and shock physics on account of their sensitivity, small size, flexibility, electromagnetic immunity, and wavelength-encoded feature. Chirped FBGs (CFBGs) are investigated as wavelength-to-position discriminators with the purpose of monitoring pressure/velocity profiles over a distance range of typically 100 mm. The use of CFBGs simplifies both sensor deployment and data retrieval and finally improves the accuracy due to the increased number of measurement data. In this paper, the metrological performance of CFBGs used as in situ distributed shock pressure/velocity gauges is investigated both theoretically and experimentally in a planar shock loading configuration with an aluminum-based flyer and target. In the intermediate range for shock stress, i.e., less than the Hugoniot Elastic Limit (HEL) of silica, CFBGs provide simultaneous measurements of both shockwave velocity and stress within the target material. A Bragg wavelength-to-stress model is proposed that takes into account (i) the state-of-stress within the target material, (ii) the stress coupling coefficient due to imperfect impedance matching between the target material and the silica fiber, (iii) the conversion of the state-of-stress into a state-of-strain within the silica fiber, and (iv) the conversion of strain data into observable Bragg wavelength shifts. Finally, the model also takes into account the pressure dependence of constitutive parameters for silica and aluminum. Experiments were performed in planar shock loading using CFBGs as stress gauges, bonded along the target axis with Araldite glue. 6061-T6 aluminum flyers were launched at several velocities by a gas gun onto targets of the same material. A free-space Czerny-Turner (CT) spectrometer and an integrated-optics Arrayed-Waveguide Grating (AWG) were both used as dynamic spectrum analyzers. Experimental Bragg wavelength shifts agree well with theoretical predictions for both elastic and hydrodynamic planar shock loading of 6061-T6 aluminum, opening up large perspectives for shock physics experiments.

Upscaling panel size for Cu plating on FOPLP (Fan Out Panel Level Packaging) applications to reduce manufacturing cost

Abstract Electrolytic metal deposition is a key process step in the manufacturing of vertical and horizontal interconnections used in today's PCBs and IC substrates on one hand and advanced packaging applications on the other hand. Historically both application areas were clearly defined and separated by different requirements in feature sizes and substrate formats. PCBs and IC substrates were based on organic large scale substrates with rather large features while advanced packaging technology is wafer based with the capability to incorporate fine features down to a few microns. The ever increasing demand of higher performance, lower cost and thinner end user devices like smartphones require intense developments and innovation in all areas of the electronic component design including the substrate and chip packaging. Latest manufacturing technologies in both areas like fan-out wafer level packaging and advanced substrates are constantly emerging and promise to be a critical piece to meet these requirements. As a consequence both areas are currently merging while creating a new application segment. This segment combines the request of small feature sizes with the manufacturability on large scale substrates. Obviously many of the traditional process technologies like plating and available equipment cannot be easily adopted and need certain developments, adaptions and improvements. In this respect, a key challenge in the area of electrolytic metal deposition is the combination of various challenging requirements: creation of feature sizes down to 2μm L/S with heterogeneous feature density on large substrates up to 600mm at excellent metal thickness uniformity and high plating speed. The paper presents latest studies and conclusions in critical performance areas of the plating process such as electrolyte fluid dynamics, impact of anode design, pulse reverse rectification and newly designed electrolytes. Finally latest test results of optimized process conditions will be discussed in detail with different feature sizes providing data of within die and within substrate uniformity. All tests are done on panel level, both organic and glass substrates. The latest findings and achievements of the discussed panel based plating process technology will support the industry to develop panel based packaging processes that meet both technical and commercial requirements.

Process intensification for scalable synthesis of ytterbium and erbium co-doped sodium yttrium fluoride upconversion nanodispersions

Rare-earth doped NaYF4 upconversion nanomaterials have found many applications from biosensing through photoelectric conversion to luminescent anti-counterfeiting. However, the scalable synthesis methods of ultrasmall NaYF4 nanoparticles are still challenging. Herein, We demonstrated that the intensified mixing of the precursor by a high-gravity rotating packed bed (RPB) reactor before the hydrothermal synthesis process enabled the preparation of ultrasmall NaYF4:Yb3+/Er3+ upconversion nanoparticles, with much smaller size, more uniform distributions and higher Er3+-doping level than those obtained in the stirred tank reactor (STR) route. In stark contrast to conventional synthetic techniques that require stringent control over several experimental variables for controlling morphologies and sizes, the process intensification approach presented here requires modification of only a single variable while enabling tremendous improvements to control the formation of NaYF4 based UCNPs with small feature size. The UCNPs dispersed well in various organic solvents (e.g. ethanol, acetone, toluene, cyclohexane, etc.), forming transparent nanodispersions with upconversion luminescence under 980 nm NIR light irradiation. The preliminary applications of NaYF4:Yb3+/Er3+ nanodispersions for upconversion luminescent transparent hybrid films and anti-counterfeiting were also demonstrated.

Monocoque shell and tube heat exchanger for thermoacoustics

Heat exchangers can be a limiting factor to thermoacoustic power density. They can also be difficult to construct because of a tendency toward many small parts due to the small size of the thermal penetration depth. We present a heat exchanger that consists of around five pieces and yet has very small feature size and is easy to construct in large numbers. A sacrificial mandrel, consisting of a sheet with a lattice of specially shaped holes, is formed by casting in a mold with a lattice of specially shaped pins. The mandrel is plated with nickel, electroless nickel, or other metal. The mandrel is then removed by melting or dissolving, leaving a monocoque tube bundle. A screen mesh may be joined to one or both faces of the monocoque to act as fins to improve thermal contact to the working fluid that flows through the tubes. Coolant flows around the tubes within the monocoque shell. For a typical device, we find that without a mesh on the monocoque, lost work is minimized with tubes on the order of 8 mm long and spaced by 0.4 mm, but with a 100-mesh copper screen on both faces, the tubes can be a more manageable 3 mm long spaced by 4 mm.

Buckling, build orientation, and scaling effects in 3D printed lattices

Cellular lightweight structures offer superior mechanical properties when compared to their bulk counterparts. Fabricating them, however, remains a challenge as even the most advanced processes exhibit considerable limitations. Material jetting, also referred to as (inkjet) 3D printing, offers multi-material capability, which, in combination with soluble support material, makes it a capable alternative to conventional processes. However, while the process is well investigated on a macro scale, these findings do not apply to small feature sizes. Here, we study the impact of buckling, build-orientation, and scaling on the mechanical properties at scales that approach the printers’ limits. Strong interaction effects and large discrepancies from macro scale parts are found. Specifically, the findings show that complete stress–strain curves can be accurately predicted when these effects are considered, whereas conventional material models tend to overestimate the mechanical properties of bend- and stretch-dominated lattices by up to an order of magnitude. This is particularly important for safety-critical and highly efficient parts. Further, the findings might help to establish the material jetting process in the field of cellular structures, which has to date been dominated by single material processes.

Fused Filament Fabrication of Small Ceramic Components.

With respect to rapid prototyping of ceramic components, there are known only a few processes (stereo lithography, binder jetting). In this work, a new process chain is described in detail, showing that ceramics can be printed in a very cost-efficient way. We developed a ceramic–polymer composite as filament material that can be printed on a low-cost fused filament fabrication (FFF) desktop printer, even with very small nozzle sizes enabling very small geometric feature sizes. The thermal post-processing, with debinding and sintering, is very close to the ceramic injection molding (CIM) process chain.

A Multilevel Zero-Inflated Model for the Study of Copper Hillocks Growth in Integrated Circuits Manufacturing

As integrated circuits (ICs) are rapidly migrating to smaller feature sizes, copper hillocks growing vertically from the copper back-end interconnects may cause inter layer metallic shorts and reliability issues. Uncovering the impact of design factors on the formation of copper hillocks is of importance for reducing the number of shorts and improving the ICs design. The purpose of this paper is twofold: 1) to experimentally investigate the mechanisms for hillock formation in a manufacturing environment and to develop a statistical model incorporating these features for more accurate predictions and 2) to determine optimal design settings to minimize hillock related short-circuits. In this paper, we describe our approach to collecting the data and our statistical model for the analysis of copper hillocks growth on ICs. To capture the low failure observations and multilevel variations, we extend the zero-inflated model, which assumes the system randomly shifts between a zero state and a count state, to a multilevel model for our problem. We first analyze the mechanism causing the zero state to determine at which level the state shift occurs. Then, the distribution of the count state is derived based on the hillocks number and the hillock height. Finally, flexible random effects distributions are incorporated to model the non-normal variations. Our analysis of the process and development of the model enable the capture of the unique characteristics of the process, and provide a platform to understand the factors governing the growth of copper hillocks in a manufacturing environment that would not have been possible if standard existing models have been applied. This has led to some previously unknown insights on the physical hillocks growth process.

Flexible, Reusable and Ultra-Thin Parylene-C/Cr Shadow Mask for Versatile Micropatterning Applications on Planar and Nonplanar Surfaces

In this paper, a reusable, flexible, and ultra-thin parylene-C/Cr shadow mask for fabricating diverse micropatterns on arbitrary surfaces is introduced. The shadow mask is composed of 3- $\mu \text{m}$ parylene-C film and 100-nm Cr layer. The flexible nature of this ultra-thin shadow mask makes it easy to attach to any surfaces. The smallest feature size of the fabricated micropatterns can reach $3~\mu \text{m}$ and the shadow mask can be reused for more than six times with good integrity and high accuracy. Various etching and deposition micropatterns with different shapes and dimensions were successfully fabricated on both flat and curved surfaces with well-defined edges and good feature transfer fidelity. With the combination of this shadow mask and an atmospheric pressure microplasma jet, selective micropatterning can be easily achieved on conventional and unconventional substrates, especially the curved and bulky objects. The potential applications of this shadow mask technology cover multiple fields, including MEMS, flexible electronics, and biomedical applications. [2018-0055]

(Invited) Using Amorphous Carbon to Enable Area-Selective Atomic Layer Deposition for Advanced Patterning Applications

The demand for transistors and memory devices with smaller feature sizes and increasingly complex architectures furthers the need for advanced thin film patterning techniques. A pre-patterned, sacrificial layer can be used as a template for bottom-up fill of new materials which would otherwise be difficult to pattern using traditional top-down lithographic methods. This work investigates initial growth of TiN, TiO2, and HfO2 thin films during thermal atomic layer deposition (ALD) onto a high density, amorphous carbon (aC) sacrificial layer. ALD of TiN by TiCl4/NH3 at 390oC, TiO2 by Ti(OCH3)4/H2O at 250oC, and HfO2 by HfCl4/H2O at 300oC on as-deposited aC films resulted in uninhibited, continuous thin film growth. We find that carbon surface reduction and passivation using a H2 plasma resulted in delayed film coalescence for TiN, TiO2, and HfO2 on the aC. After 200 TiN cycles on H2 plasma-treated aC, Rutherford backscattering spectrometry shows Ti levels below the detection limit (8×1013 at/cm2), whereas SiO2 or Si3N4 substrates show TiN growth of ~6 nm, corresponding to a selectivity of ~200:1. Exposing plasma-treated aC to H2O induces nucleation for TiN ALD, consistent with favorable nucleation on hydroxyl sites. Therefore, the H2O co-reagent in TiO2 and HfO2 ALD contributes to loss of selectivity compared to TiN ALD using NH3. Furthermore, we demonstrate the use of the Avrami Equation to model the nucleation behavior on plasma-treated aC, providing useful insights into process improvements for increased selectivity. We confirm scaling of selectivity to sub 50 nanometer patterns using 45 nm aC/Si3N4 line/space patterns, where 3.5 nm TiO2 and 5.8 nm TiN films are deposited on Si3N4 with minimal particle formation on aC, with selectivity loss primarily on feature corners and edges. We conclude that improved scaling of selectivity to nanometer scale patterns can be achieved by optimizing surface loading and extent of plasma exposure, and by further understanding shape effects in nanoscale surface plasma modification.

Aging-Aware Workload Management on Embedded GPU Under Process Variation

Graphics Processing Units (GPUs) have been employed in embedded systems to handle increased amounts of computation and to satisfy the timing requirement. Due to the small feature size, chip aging and within-die parameter variations have been considered to be among the challenging problems for state-of-the-art processors, including GPUs. In order to deal with the process variation, several processors use chip-level guardbanding, which uses the lowest operating frequency that results in a significant chip-level performance drop. Other processors improve their performance efficiency through core-level guardbanding that may use a different operating frequency for each core. Existing aging management techniques are based on the chip-level guardbanding, which assigns the same number of instructions to the cores that have the same aging status. However, in the presence of the process variation, existing aging management techniques have a limitation in minimizing the aging effect because each core has a different amount of stress for the same number of instructions. In order to tackle this problem, we propose a low-overhead aging and process variation aware workload management technique for embedded GPUs. The proposed technique considers the process variation and the current aging status together, and assigns a different number of instructions to clusters to minimize the aging effect in the presence of process variation. Results show that our technique improves the GPU aging in over 95 percent of cases whereas the state-of-the-art compiler-based technique improves the GPU aging in 72.25 percent of cases. Moreover, compared to the compiler-based technique, our technique reduces the performance overhead by 40 percent while achieving almost the same GPU aging improvement.

The Role of Liquid Ink Transport in the Direct Placement of Quantum Dot Emitters onto Sub-Micrometer Antennas by Dip-Pen Nanolithography.

Dip-pen nanolithography (DPN) is used to precisely position core/thick-shell ("giant") quantum dots (gQDs; ≥10 nm in diameter) exclusively on top of silicon nanodisk antennas (≈500 nm diameter pillars with a height of ≈200 nm), resulting in periodic arrays of hybrid nanostructures and demonstrating a facile integration strategy toward next-generation quantum light sources. A three-step reading-inking-writing approach is employed, where atomic force microscopy (AFM) images of the pre-patterned substrate topography are used as maps to direct accurate placement of nanocrystals. The DPN "ink" comprises gQDs suspended in a non-aqueous carrier solvent, o-dichlorobenzene. Systematic analyses of factors influencing deposition rate for this non-conventional DPN ink are described for flat substrates and used to establish the conditions required to achieve small (sub-500 nm) feature sizes, namely: dwell time, ink-substrate contact angle and ink volume. Finally, it is shown that the rate of solvent transport controls the feature size in which gQDs are found on the substrate, but also that the number and consistency of nanocrystals deposited depends on the stability of the gQD suspension. Overall, the results lay the groundwork for expanded use of nanocrystal liquid inks and DPN for fabrication of multi-component nanostructures that are challenging to create using traditional lithographic techniques.

Hazy Al₂O₃-FTO Nanocomposites: A Comparative Study with FTO-Based Nanocomposites Integrating ZnO and S:TiO₂ Nanostructures.

In this study, we report the use of Al2O3 nanoparticles in combination with fluorine doped tin oxide (F:SnO2, aka FTO) thin films to form hazy Al2O3-FTO nanocomposites. In comparison to previously reported FTO-based nanocomposites integrating ZnO and sulfur doped TiO2 (S:TiO2) nanoparticles (i.e., ZnO-FTO and S:TiO2-FTO nanocomposites), the newly developed Al2O3-FTO nanocomposites show medium haze factor HT of about 30%, while they exhibit the least loss in total transmittance Ttot. In addition, Al2O3-FTO nanocomposites present a low fraction of large-sized nanoparticle agglomerates with equivalent radius req > 1 μm; effectively 90% of the nanoparticle agglomerates show req < 750 nm. The smaller feature size in Al2O3-FTO nanocomposites, as compared to ZnO-FTO and S:TiO2-FTO nanocomposites, makes them more suitable for applications that are sensitive to roughness and large-sized features. With the help of a simple optical model developed in this work, we have simulated the optical scattering by a single nanoparticle agglomerate characterized by bottom radius r0, top radius r1, and height h. It is found that r0 is the main factor affecting the HT(λ), which indicates that the haze factor of Al2O3-FTO and related FTO nanocomposites is mainly determined by the total surface coverage of all the nanoparticle agglomerates present.

Double-Layer Morphologies from a Silicon-Containing ABA Triblock Copolymer.

A combined experimental and self-consistent-field theoretical (SCFT) investigation of the phase behavior of poly(stryrene- b-dimethylsiloxane- b-styrene) (PS- b-PDMS- b-PS, or SDS32) thin films during solvent vapor annealing is presented. The morphology of the triblock copolymer is described as a function of the as-cast film thickness and the ratio of two different solvent vapors, toluene and heptane. SDS32 formed terraced bilayer morphologies even when the film thickness was much lower than the commensurate thickness. The morphology transitioned between bilayer cylinders, bilayer perforated lamellae, and bilayer lamellae, including mixed structures such as a perforated lamella on top of a layer of in-plane cylinders, as the heptane fraction during solvent annealing increased. SCFT modeling showed the same morphological trends as a function of the block volume fraction. In comparison with diblock PS- b-PDMS with the same molecular weight, the SDS32 offers a simple route to produce a diversity of well-ordered bilayer structures with smaller feature sizes, including the formation of bilayer perforated lamellae over a large process window.

Features in Microfluidic Paper-Based Devices Made by Laser Cutting: How Small Can They Be?

In this paper, we determine the smallest feature size that enables fluid flow in microfluidic paper-based analytical devices (µPADs) fabricated by laser cutting. The smallest feature sizes fabricated from five commercially available paper types: Whatman filter paper grade 50 (FP-50), Whatman 3MM Chr chromatography paper (3MM Chr), Whatman 1 Chr chromatography paper (1 Chr), Whatman regenerated cellulose membrane 55 (RC-55) and Amershan Protran 0.45 nitrocellulose membrane (NC), were 139 ± 8 µm, 130 ± 11 µm, 103 ± 12 µm, 45 ± 6 µm, and 24 ± 3 µm, respectively, as determined experimentally by successful fluid flow. We found that the fiber width of the paper correlates with the smallest feature size that has the capacity for fluid flow. We also investigated the flow speed of Allura red dye solution through small-scale channels fabricated from different paper types. We found that the flow speed is significantly slower through microscale features and confirmed the similar trends that were reported previously for millimeter-scale channels, namely that wider channels enable quicker flow speed.

Area-Selective Atomic Layer Deposition of TiN, TiO2, and HfO2 on Silicon Nitride with inhibition on Amorphous Carbon

The demand for transistors and memory devices with smaller feature sizes and increasingly complex architectures furthers the need for advanced thin film patterning techniques. A prepatterned, sacrificial layer can be used as a template for bottom-up fill of new materials which would otherwise be difficult to pattern using traditional top-down lithographic methods. This work investigates initial growth of TiN, TiO2, and HfO2 thin films during thermal atomic layer deposition (ALD) onto a high density, amorphous carbon (aC) sacrificial layer. ALD of TiN by TiCl4/NH3 at 390 °C, TiO2 by Ti(OCH3)4/H2O at 250 °C, and HfO2 by HfCl4/H2O at 300 °C on as-deposited aC films resulted in uninhibited, continuous thin film growth. We find that carbon surface reduction and passivation using a H2 plasma resulted in delayed film coalescence for TiN, TiO2, and HfO2 on the aC. After 200 TiN cycles on H2 plasma-treated aC, Rutherford backscattering spectrometry shows Ti levels below the detection limit (8 × 1013 at/cm2), where...

Comparative analysis of adiabatic logic challenges for low power CMOS circuit designs

In a deep sub-micrometer regime as the scaling improves (reduction in feature size), gate oxide becomes thin and threshold voltage gets reduced, and thus the contribution in power dissipation due to leakage currents increases. Consequently, leakage currents in small feature size devices become a critical factor for low power applications. As the feature size has been reduced very much already, therefore it becomes very important to identify new techniques for power reduction instead of decreasing the feature size. Energy recovery technique is such a prominent technique which recycles the stored charge at different nodes and reduces power dissipation significantly. This paper reviews various energy recovery techniques based on different adiabatic logics. Analysis and comparison of different adiabatic logic techniques based on various parameters such as, the frequency of operation, µm technology used, supply voltage, the number of devices used has been done successfully in this paper. This paper explores various aspects of energy recovery logics.