RF Regime Research Articles

(Invited, Digital Presentation) Copper Nanowire 3-D Interconnects for Mm-Wave Applications

Small, lightweight mobile devices are the beneficiaries of fabrication miniaturization that follow Moore’s law predictions, advances in complex integration concepts, and wireless technology. Successful implementations have therefore stimulated unprecedented growth in mobile applications. Within these miniaturized devices, contact electrodes with small form factors in some applications are needed but unfortunately present many challenges and can lead to unwanted parasitic effects. Identifying ways to meet this need without introducing parasitic effects is essential to minimize signal distortion and loss in integrated circuits. The plethora of applications, however, produce large number of users and also generate extremely large amounts of data that require higher data rates. Higher frequency designs satisfy bandwidth requirements and maintain miniature size; unfortunately, this comes at a cost. When operating frequencies increase, available power decreases due to transistor technology limitations and the corresponding shrinkage in circuit size results in higher resistance leading to more power consumption. To address this conundrum, approaches are needed that allow losses to much be managed, and ideally reduced to achieve the desired performance requirements.This talk will present the investigation of copper nanowire (CuNW) technology for use in millimeter wave regime (30 GHz to 300 GHz) interconnect design in silicon integrated circuits. The parallel nature of nanowires to behave like bundles offers the potential to minimize loss and parasitic effects at millimeter wave frequencies. Co-integration of CuNW into coplanar waveguide (CPW) interconnect configurations that are single and multi-layer architectures will be discussed. Two types of interconnects are studied: vertical via and CuNW integrated into CPW lines. The findings from the study of these structures will include a discussion on the fabrication and characterization methods used for each technology followed by the loss performance results observed for the different types of designs.At 40 and 60 GHz, vertical CuNW via loss values of 0.095 dB and 0.149 dB was observed, respectively. These responses were lower than those of other via technologies and comparable to those in anodized aluminum substrates. Thus, they were favorable and indicate that CuNW can be used in a co-integrate manner to incorporate small contact features into designs that can maintain or reduce loss in the millimeter wave regime. CuNWs integrated CPW interconnects can also be used as a transmission line. In this case, loss responses, observed in the millimeter wave regime, can be reduced. In one design, loss values of 0.48 dB/mm and 0.59 dB/mm at 90 and 180 GHz, respectively, were determined, suggesting that conductor loss can be reduced in upper millimeter regime. At these frequencies, higher order mode suppression is essential to minimize unwanted substrate losses. Another design, however, improved losses in the low RF and microwave frequency regime, suggesting that low frequency designs can also experience conductor loss reduction. The conclusion thus far is that CuNW co-integration into CPW lines show promise for improving the performance of interconnect design across the RF to millimeter-wave spectrum when designed carefully.

Theoretical Prediction of Electrical Conductivity Percolation of Poly(lactic acid)-Carbon Nanotube Composites in DC and RF Regime.

Polymer composites based on polylactic acid (PLA) reinforced with 0.25-5 wt.% of carbon nanotubes (CNTs) were synthesized by melt blending. The static (DC) and microwave (RF) electrical conductivity have been investigated on the PLA-CNT composites. The electrical percolation threshold has been theoretically determined using classical models of percolation in order to predict the conductivity of the different nanocomposites. Through the fitting process, it has been found that the percolation threshold is obtained at 1 wt.% of CNTs in the DC regime and reached below 0.25 wt.% of CNTs in the microwave regime. Among the Mamunya, McLachlan, or GEM models, the McCullough model remarkably fits the experimental DC and RF electrical conductivities. The obtained results are correlated to the electrical properties of a range of CNT-based composites, corresponding to the percolation threshold required for a three-dimensional network of CNTs into the polymer matrix.

Visualization of Metasurface Eigenmodes with Magnetic Resonance Imaging

Standard techniques to image the eigenmodes of a metasurface are based on collecting signals from various spatial positions via a probe on a motorized platform---typically a slow procedure, and only a two-dimensional near-field profile can be measured in one scan. This work demonstrates an innovative way to visualize and study metasurface eigenmode profiles through magnetic resonance imaging. The approach offers a practical, nonperturbing, rapid means of imaging the eigenmodes of metasurfaces or volumetric structures, which is significant to obtain insight into the physics of artificial materials in the rf regime.

Feed competition reduces heritable variation for body weight in Litopenaeus vannamei

BackgroundCompetition is a common social interaction among shrimp and depending on its intensity, it can affect heritable variation and response to selection. Little is known about the variance of indirect genetic effects (IGE) under competitive and non-competitive conditions in shrimp. In this study, we used extended mixed linear models to estimate genetic parameters for the direct genetic effect (DGE) and IGE on body weight in Litopenaeus vannamei raised under ad libitum (AF, non-competitive environment) and restricted (RF, competitive environment) feeding regimes.ResultsEstimates of heritabilities for body weight obtained with a traditional animal model (i.e. without accounting for IGE) were 0.11 ± 0.09 under AF and 0.25 ± 0.11 under RF. With extended animal models that accounted for IGE, the corresponding estimates for body weight were 0.07 ± 0.08 and 0.34 ± 0.11. Thus, heritabilities were higher under the RF regime than under the AF regime, regardless of whether IGE was accounted for or not. The log-likelihood ratio test revealed significant IGE under the RF regime. Although estimates of indirect genetic variance were low (0.0023 ± 0.0013 for AF and 0.0028 ± 0.0012 for RF), they contributed substantially to the total heritable variance: 66.8% for AF and 692.2% for RF. The total heritable variance was smaller under the RF regime (0.7 ± 1.3) than under the AF regime (5.8 ± 2.6) because of the high contribution of the negative covariance between DGE and IGE (− 7.03). Estimates of the correlation between DGE and IGE were 0.32 ± 0.47 under AF and − 0.93 ± 0.15 under RF, those of DGE and IGE for body weight between both regimes were 0.94 ± 0.07 and 0.67 ± 0.20, respectively, and those of IGE for body weight with DGE for survival were − 0.12 ± 0.22 under AF and − 0.58 ± 0.20 under RF.ConclusionsThese results indicate that strong competitive interactions occurred under the RF regime in L. vannamei. Significant reranking and variation in IGE of individuals were observed between the two feeding regimes. Strong competitive interactions reduced the total heritable variation for body weight when food was restricted. These results indicate that the extent of competition among L. vannamei depends on the feeding regime applied and that this competition affects the genetic basis of body weight.

Thermal and electrical performance investigation of FinFET with encased air-gap gate sidewalls from spacer encapsulation layer material and structure parameter perspectives

We explore the potential benefits of using spacer engineering to improve Bulk FinFET electrical and thermal characteristics. Based on the comparative study of five different spacer configurations, the spacer with encased air-gap and Si3N4 encapsulation layer is regarded as the most promising gate sidewall scheme for the advanced technology node due to the reduced instinct delay and improved SHEs suppression. The further investigation of the encased air-gap spacer with Si3N4 demonstrates that spacer structure parameters have modulation effects on device performance. With the analysis of the normalized RF, analog, digital, thermal and subthreshold regime property parameters, the suitable air-gap percentage window and the determined optimum spacer structure parameters of 14 ​nm Bulk FinFET are proposed.

Mechanical properties, chemical analysis and evaluation of antimicrobial response of Si-DLC coatings fabricated on AISI 316 LVM substrate by a multi-target DC-RF magnetron sputtering method for potential biomedical applications

In this study silicon doped diamond-like carbon (Si-DLC) coatings were synthesized on two substrates: silicon and AISI 316LVM stainless steel using a multi-target DC-RF magnetron sputtering method. The Si content in the films ranged between 4 and 16at.%, and was controlled by the electrical power applied in RF regime to Si cathode target.The character of the chemical bonds was revealed by FTIR analysis. With the addition of silicon the hydroxyl absorption (band in the range of 3200–3600cm−1) increased what suggests more hydrophilic character of the coating. There were also observed significant changes in bonding of Si atoms. For low content of dopant, Si-O-Si bond system is predominant, while for the highest content of silicon there is an evidence of the shift to Si-C bonds in close proximity to methyl groups. The Raman spectroscopy revealed that the G peak position is shifted to a lower wavenumber and the ID/IG ratio decreased with increasing Si content, which indicates an increase in the C-sp3 content. Regardless of the coatings’ composition, the improvement of hardness in comparison to pure substrate material (AISI 316 LVM) was observed. Although the reduction of the level of hardness from the level of 10.8GPa for pure DLC to about 9.4GPa for the silicon doped coatings was observed, the concomitant improvement of films adhesion with higher amount of Si was revealed. Although incorporation of the dopant to DLC coatings increases the number of E. coli cells which adhered to the examined surfaces, the microbial colonisation remains on the level of substrate material.The presented results prove the potential of Si-DLC coatings in biomedical applications from the point of view of their mechanical properties.

Challenges in packaging of IR detectors - technology of elastic electrical connections

This paper describes the study on flexible connections application in IR detector package. Such a connection is used between two modules in single package. One module is IR detector operating at -73 °C, other is electronic controlling circuit operating at room temperature. Flexible electrical connection must provide good electrical parameters in both DC and RF regime as well as poor thermal conductivity. 35 μm epoxy-phenolic foil with 5 μm Ni film and special RF compatible Ground-Signal-Ground geometry was successfully applied as connection. Low eutectic temperature InSn solder was used for soldering flexible connection to both IR detector and electronic circuit. Two types of soldering processes were investigated: bump and lap type. Flexible connection was tested for DC operation with long term stability test and RF parameters were determined. Authors found that both joining techniques are suitable for application in IR photodetector devices. However lap type joint is easier to apply in technological process, therefore it will be applied in final assembly.

High-frequency signal transmission through single-atom contacts of Au and Pt

Signal transmission through atom-sized contacts of Au and Pt has been studied at room temperature for frequencies from 9 kHz to 1 GHz and for conductances (1−10)G0 (G≡2e2/h is the quantum unit of conductance). We measured the frequency spectrum of S parameter S21=|S21|eiθ and found θ∼0 up to 1 GHz for all contacts irrespective of their conductance. Our observations directly prove that the atom-sized contacts of Au and Pt, including their single-atom contacts, behave as a pure resistance in the RF regime.

ANALYSIS OF NOVEL FRACTAL OPTICAL ANTENNA ARRAYS - A CONCEPTUAL APPROACH

Fractal antennas have undergone dramatic changes since they were flrst considered for wireless systems. Numerous advancements are developed both in the area of fractal shaped elements and fractal antenna array technology for fractal electrodynamics. This paper makes an attempt of applying the concept of fractal antenna array technology in the RF regime to optical antenna array technology in the optical regime using nonlinear array concepts. The paper further discusses on the enhancement of nonlinear array characteristics of fractal optical antenna arrays using nonlinearities in coupled antennas and arrays in a conceptual manner.

AN ANALYSIS OF JUNCTION DISCONTINUITY EFFECTS IN MULTI-ELEMENT COUPLED LINES AND ITS DIMINUTION AT DESIGNING STAGE

The analysis and design of the multi-element coupled lines, in conjunction with the junction discontinuity efiect, is presented, and its applicability in high power rf regime is discussed. Junctions are usually employed to connect two difierent coupled elements, which gives rise to undesirable reactance, i.e., junction discontinuity efiect. These efiects are found prominent in the high power coupled lines for HF and VHF applications because of its large structural dimensions. The design and simulation of 3-element, 8:34 § 0:2dB coupled line section rated for 38 to 112MHz and 200kW has been performed. The simulated results are signiflcantly deviated from the theoretically calculated ones where the discontinuity efiect is usually ignored. A generalized theoretical procedure is developed to take into account the efiect of junction discontinuity at the designing stage. The theory is applied to the 3-element 8:34 § 0:2dB coupled-line section, and simulation is performed by using standard Ansoft HFSS software. The HFSS simulation results are in close agreement with the theoretical predictions.

ANALYSIS OF NONLINEAR FRACTAL OPTICAL ANTENNA ARRAYS - A CONCEPTUAL APPROACH

Fractal antennas have undergone dramatic changes since they were flrst considered for wireless systems. Numerous advancements are developed both in the area of fractal shaped elements and fractal antenna array technology for fractal electrodynamics. This paper makes an attempt of applying the concept of fractal antenna array technology in the RF regime to optical antenna array technology in the optical regime using nonlinear array concepts. The paper further discusses on the enhancement of nonlinear array characteristics of fractal optical antenna arrays using nonlinearities in coupled antennas and arrays in a conceptual manner.

Negative capacitor paves the way to ultra-broadband metamaterials

Experimental demonstration of the overcoming of basic dispersion-energy constraints in metamaterials with the help of active non-Foster negative capacitors is reported. The experimental metamaterial operates in RF regime, and it is based on air transmission line loaded with negative capacitors. Measurement results clearly show almost dispersionless Epsilon-Near-Zero behavior, accompanied with superluminal both phase and group velocities, over a bandwidth of more than four octaves (2 MHz-40 MHz). The principle of periodic loading of transmission line with negative capacitors may find applications in ultra-broadband active metamaterials for antennas and cloaking technology.

Real-time synchronous imaging of electromechanical resonator mode and equilibrium profiles

Interferometric imaging of normal mode dynamics in electromechanical resonators, oscillating in the rf regime, is demonstrated by synchronous imaging with a pulsed nanosecond laser. Profiles of mechanical modes in suspended thin film structures and their equilibrium profiles are measured through all-optical Fabry-Perot reflectance fits to the temporal traces. As a proof of principle, the mode patterns of a microdrum silicon resonator are visualized, and the extracted vibration modes and equilibrium profile show good agreement with numerical estimations.

Time domain modeling of plasmas at RF time-scales

Results from tokamak experiments such as PPPL's NSTX indicate that significant anomalous power absorption can occur in the edge of the fusion plasma. Understanding of this phenomenon is a critical issue for analysis of RF heating scenarios on the ITER fusion experiment. Two probable edge absorption candidates, rf sheath losses and parametric decay instability, are both inherently non-linear, and likely to depend significantly on non-axi-symmetric geometric detail in the vicinity of the antenna structures. Analysis of these phenomenon is beyond the capabilities of existing axi-symmetric frequency-domain linear-solvers used for analysis of heating and current drive in core fusion plasma, and so we are augmenting our analysis capability with the time-domain 3-D general-geometry electromagnetic and particle-in-cell simulation framework, Vorpal [1]. This framework is a modern object-oriented software package, which has demonstrated fast scalable operation on clusters of over 1000 cpu's, a necessity for this type of calculation. We have successfully introduced into this framework an implicit plasma solver [2], in order to accurately treat electromagnetic plasma wave characteristics in the wide range of plasma conditions occurring from edge plasma to core plasma, including situations where the plasma frequency is not resolvable at the rf time-scales of interest, and including sharp plasma resonances and cutoff behaviours common in the rf regime. We present benchmarking of this new plasma solver for 1-D, 2-D, and 3-D scenarios. We also discuss implementation plans for non-linear sheath boundary models, non-linear edge-plasma conditions leading to parametric decay, and also tracking of high-energy particles in core-heating scenarios, where issues of finite-banana-width effects and superadiabaticity remain outside the scope of the existing frequency-domain solvers.

Nanostructured porous silicon as thick electrical insulator for radio-frequency applications

Nanostructured porous silicon layers are studied for the purpose of their use as electrical insulators between mono-crystalline silicon substrates and integrated planar radio frequency (rf) devices. The capacitive nature of the layers with a tangent loss lower than 10 -2 is demonstrated in the 10 5 -10 9 Hz range by means of complex impedance measurements and rf regime experiments on micro L-C resonant circuits. Finally, the insulating capabilities of nanostructured porous silicon were evaluated using numerical simulations combined with our experimental data. A minor contribution of the porous silicon residual conductance to the rf energy loss is found.

Surface-Potential-Based Metal–Oxide–Silicon-Varactor Model for RF Applications

We have developed a surface-potential-based metal–oxide–silicon (MOS)-varactor model valid for RF applications up to 200 GHz. The model enables the calculation of the MOS-varactor capacitance seamlessly from the depletion region to the accumulation region and explicitly considers the carrier-response delay causing a non-quasi-static (NQS) effect. It has been observed that capacitance reduction due to this non-quasi-static effect limits the MOS-varactor application to an RF regime.

MESFET fabricated on deuterium-implanted polycrystalline diamond

Cr- and Al-gate MESFETs have been fabricated on deuterium-implanted polycrystalline diamond and characterized both in DC and RF regime. Their performances are compared with those of similar devices fabricated on plasma hydrogenated polycrystalline diamond, which suffer for instabilities related to the large sensitivity of the channel to surface adsorbates. It is shown that similar characteristics can be achieved both in MESFETs with deuterium-implanted and plasma hydrogenated diamond.

Fluoropolymer Coating of Medical Grade Poly(vinyl chloride) by Plasma‐Enhanced Chemical Vapor Deposition Techniques

AbstractSummary: Medical grade poly(vinyl chloride) was modified by RF plasma‐deposition of teflon‐like coatings to create a platform for the physisorption of PEO‐containing copolymers, Pluronics®. Thin teflon‐like coatings were deposited in an RF‐plasma reactor by plasma‐enhanced chemical vapor deposition (PE‐CVD) methods, using hexafluoroethane (C2F6) as a precursor and H2 as a carrier gas. A systematic study of the deposition parameters, C2F6 percentage in the C2F6‐H2 gas feed, power input and pressure was completed using X‐ray Photoelectron Spectroscopy and water contact angle measurements to characterize the various coatings. The surface analysis results were further correlated to the existing ion‐activated growth model. XPS results indicated that the coatings which had the maximum fluorine incorporation, as determined by the F/C ratio, or CFx functional groups, had the highest surface hydrophobicity. The parameters that were determined to yield the maximum contact angle (104°) in the continuous power, RF regime were a high C2F6 percentage (80%) in the C2F6‐H2 gas feed and the mid‐range power input and pressure values tested (30 W and 0.4 mbar).Change in C 1s high resolution scans and contact angle achieved following teflon‐like deposition on native PVC.imageChange in C 1s high resolution scans and contact angle achieved following teflon‐like deposition on native PVC.

High-Density RF MIM Capacitors Using High-k La2 O 3 Dielectrics

The integrity of the metal-insulator-metal (MIM) capacitor with high-k dielectrics formed using a 400°C back-end process was investigated. A very high capacitance per unit area of 9.2 fF/μm2 was achieved for MIM capacitors at 1 MHz, significantly reducing the chip size of radio frequency (rf) circuits. A mathematical derivation, involving measured S parameters, yielded the small voltage-dependent capacitance ppm at 1 GHz, indicating that the precision capacitor circuit can be applied in the rf regime. Furthermore, such a high capacitance density can be maintained as the frequency is increased from 10 KHz to 20 GHz with a large Q factor ⩾90. © 2004 The Electrochemical Society. All rights reserved.

Mechanical gating of coupled nanoelectromechanical resonators operating at radio frequency

We report measurements on hybrid gold/silicon suspended nanostructures operating as electromechanical resonators in the rf regime. The device consists of two nanoresonators operating as mechanical gating elements. We demonstrate this gating mechanism by tuning the mechanical modes of the device. Detailed numerical calculations are performed to model the device.