Radiation induced loss properties and hardness enhancement technique for ErYb doped fibers for avionic applications

We present radiation reliability properties and their enhancement of ErYb doped optical fibers in terms of induced loss and lifetime prediction via master curve analysis method. In this study, we are primarily concerned with the effects of ionizing radiation on the performance of double cladded ErYb doped optical fibers in an accelerated low dose γ-radiation environment (i.e. <120 rad/h rate) for high power optical amplifiers to be used in satellite communication systems. We demonstrate a novel method that utilizes pre-radiation exposure and thermal annealing, for enhancing radiation hardness of the fibers with respect to induced optical loss and lifetime prediction. Based on this method, we are able to modify radiation induced loss-rate properties of the fiber with an initial loss penalty, realizing overall loss-budget improvement for relatively long-term deployment (i.e. >5 years). In a direct comparison to non-hardened ErYb doped fibers, we demonstrate approximately 0.16 dB/m of radiation induced loss improvement including an initial loss penalty of 0.14 dB for radiation-hardened fibers over a 10-year duration in a natural low dose (i.e. <0.3 rad/h) radiation environment, i.e. low earth orbit.     

Synthesis and characterization of sub-micron sized copper–ruthenium–tantalum composites for interconnection application

Sub-micron sized ruthenium and tantalum reinforced copper composites as suitable material for electronic interconnection applications was synthesized using high temperature high pressure technique. High purity sub-micron starting powders were blended in a turbula mixer at varying compositions and consolidated at temperature of 850 °C and pressure of 30 MPa for 30 min. The density, phase composition, microstructure, hardness and electrical conductivity of the resulting materials were investigated. The addition of 2.5 vol% ruthenium improved the density of the pure sintered Cu from 97.20% of the theoretical to 99.89% and increased the Vickers hardness value from 114.2 HV to 127.8 HV. Tantalum addition was found to inhibit copper grain growth during sintering. The electrical resistivity of copper based composites remained relatively low with the addition of reinforcement materials.     

Multiband monopole antenna loaded with Complementary Split Ring Resonator and C-shaped slots

This paper presents a compact semi circular monopole antenna loaded with Complementary Split Ring Resonator (CSRR) and two C-shaped slots is proposed for Global System for Mobile Communication (GSM), Worldwide Interoperability for Microwave Access (WiMAX) and C-band applications. The size of the proposed antenna is 20 × 20 × 0.5 mm³. The resonance frequency of WiMAX (3.73 GHz) is achieved by introducing CSRR slots on the ground plane. To realize multiband characteristics for GSM (1.77 GHz), WiMAX (2.6 GHz) and C-band (4.15 GHz), two C-shaped slots of quarter wavelength are introduced in radiating element. The extraction procedure of negative permittivity for the proposed CSRR is discussed in detail. The proposed antenna is fabricated and measured. Simulated and measured results are in good agreement. Omni directional radiation pattern is obtained in H-plane and bi directional radiation pattern is obtained in E-plane. Parametric study of CSRR and C-shaped slot are examined to obtain best results. The proposed antenna has significant advantages, including low profile, miniaturization ability, and good impedance matching.     

Anodic Ta2O5 for CMOS compatible low voltage electrowetting-on-dielectric device fabrication

This paper reports a CMOS compatible fabrication procedure that enables electrowetting-on-dielectric (EWOD) technology to be post-processed on foundry CMOS technology. With driving voltages less than 15 V it is believed to be the lowest reported driving voltage for any material system compatible with post-processing on completed integrated circuits wafers. The process architecture uses anodically grown tantalum pentoxide as a pinhole free high dielectric constant insulator with an overlying 16 nm layer of Teflon-AF^®, which provides the hydrophobic surface for droplets manipulation. This stack provides a very robust dielectric, which maintains a sufficiently high capacitance per unit area for effective operation at a reduced voltage (15 V) which is more compatible with standard CMOS technology. The paper demonstrates that the sputtered tantalum layer used for the electrodes and the formation of the insulating dielectric can readily be integrated with both aluminium and copper interconnect used in foundry CMOS.     

Multi-Poisson process analysis of real-time soft-error rate measurements in bulk 65 nm and 40 nm SRAMs

Altitude and underground real-time soft error rate (SER) measurements on SRAM circuits have been analyzed in terms of independent multi-Poisson processes describing the occurrence of single events as a function of bit flip multiplicity. Applied for both neutron-induced and alpha particle-induced SERs, this detailed analysis highlights the respective contributions of atmospheric radiation and alpha contamination to multiple cell upset mechanisms. It also offers a simple way to predict by simulation the radiation response of a given technology for any terrestrial position, as illustrated here for bulk 65 nm and 40 nm SRAMs.     

Design of an integrated UWB antenna with dual band notch characteristics

A miniaturized couple-line-fed planar ultra-wideband (UWB) antenna is proposed, which has a dual band-notched characteristic as well as two integrated monopoles. Narrowband notches are generated at frequencies of 3.5 GHz and 5.5 GHz using independently controlled bent resonators, whereas the monopoles are designed for radiation at 900 MHz and 2.4 GHz. The proposed design is simulated with full wave solvers and verified with measurements. A good agreement is observed between the simulations and measurements for the antenna's return loss, gain and radiation pattern performances.     

Design,fabrication and measurement of triple band frequency reconfigurable antennas for portable wireless communications

In this paper two triple-band monopole antennas are proposed for portable wireless applications such as WiFi, WiMAX and WLAN. Two different geometrical structures are used for the radiating elements of these antennas, each printed on a low cost FR-4 substrate. Truncated metallic copper ground is used to attain optimum radiation pattern and better radiation efficiency. The frequency of the antennas is reconfigured using a lumped-element switch. The proposed antennas covers three frequency bands 2.45, 3.50 and 5.20 GHz depending upon the switching conditions. Both antennas works with an optimum gain (1.7–3.4 dB), bandwidth (6–35%), VSWR (<1.5) and radiation efficiency (85–90%). Due to its affordable size (1.6 × 35 × 53 mm³), the antennas can be used in modern and portable communication devices such as laptops, iPads and mobile phones. The prototype of the antennas are fabricated and the measurements and simulations are found in close agreement.     

Nanomechanical properties of Ag solder bumps doped with Pd and Au

As an approach to increasing their reliability, we doped Ag solder bumps with Pd and Au alloys to enhance their creep resistance, which we characterized using a nanoindentation technique. The hardnesses of the pure Ag and the Ag solders doped with Pd:3%, Pd:5%, and Pd:2%-Au:3% were 0.6 ± 0.1, 1.8 ± 0.2, 2.8 ± 0.3, and 3.1 ± 0.5 GPa, respectively. Although the hardness of the Ag solder was enhanced significantly when it contained Pd:2%-Au:3%, it exhibited a lower creep exponent (n > 2). The mechanism of the thermal recovery of the sample appears to be associated with activation of dislocation sources—also the reason for the decrease in hardness. The compounds doped with Pd:2%-Au:3% displayed significantly greater bond strengths and creep exponents, whereas the Pd-only compounds exhibited poorer reliability.     

Impact toughness,hardness and shear strength of Fe and Bi added Sn-1Ag-0.5Cu lead-free solders

In this study, the new Fe/Bi-bearing Sn-1Ag-0.5Cu (SAC105) solder alloys were studied for their mechanical properties, including impact toughness, hardness and shear strength. Charpy impact tester with impact speed of 5.4 m/s was used to determine the impact absorbed energy during impact tests. With the 0.05 wt.% Fe and 1 wt.% Bi addition to the SAC105 alloy, the impact absorbed energy increased from 8.1 J to 9.7 J by about 20% and literally no further improvement was observed by increasing the Bi content in the alloy. Vickers hardness tests were performed with a load of 245.2 mN and load dwell time of 10 s. The addition of Fe/Bi to SAC105 increased the hardness of the alloy from 10.5 HV to 22.6 HV showing an increase of more than two fold. Shear tests were performed with a shear speed of 0.25 mm/min. Shear strength almost doubled for the Fe/Bi added SAC105, as compared to the base alloy, increasing from 17.8 MPa to 34.3 MPa. The microstructure study shows that Bi is dissolved in the solder bulk and strengthens the solder alloys by its solid solution strengthening mechanism. The β-Sn grain size, as revealed by cross-polarized optical microscopy, significantly reduced from 60–100 μm to 20–40 μm with Fe/Bi addition to SAC105. The micrographs of field emission scanning electron microscopy (FESEM) with backscattered electron detector and their further analysis via ImageJ software indicated that Fe/Bi addition to SAC105 significantly reduced the Ag₃Sn and Cu₆Sn₅ IMCs size and refined the microstructure. These changes in the microstructure of Fe/Bi added SAC105 expectedly resulted in such improvement in their mechanical properties.     

Offset-fed complementary split ring resonators loaded monopole antenna for multiband operations

A miniaturized multiband monopole antenna based on rectangular-shaped Complementary Split Ring Resonators (CSRRs) with offset-fed microstrip line is proposed for Global System for Mobile Communication (GSM) and Wireless Local Area Network (WLAN) applications. The proposed antenna is fabricated on a FR-4 substrate having a dielectric constant (ɛ_r) of 4.4 within a small size of 19.18 × 22.64 × 1.6 mm³. CSRRs in the monopole antenna create a multiband characteristics and bandwidth improvement, which is analyzed by use of the precise quasi-static design equations and electromagnetic simulation software (HFSS version 13). By selecting a proper offset-fed microstrip line, it is capable to achieve 50 Ω characteristic impedance and good impedance matching. The parameter extraction procedure of the metamaterial property of the CSRRs is enlightened in detail, by which the negative permittivity existence and the new resonance frequencies are verified. Simulated and measured result coincides with each other. The measured H-Plane (azimuthal plane) exhibits omnidirectional radiation pattern and E-plane (elevation plane) shows a dipole like bidirectional radiation pattern. The proposed antenna has adequate advantages, including simple design, small size, lower return loss and capable of multiband operations.     

Flexible Chip-on-Flex (COF) and embedded Chip-in-Flex (CIF) packages by applying wafer level package (WLP) technology using anisotropic conductive films (ACFs)

Due to increasing demand for higher performance, greater flexibility, smaller size, and lighter weight in electronic devices, extensive studies on flexible electronic packages have been carried out. However, there has been little research on flexible packages by wafer level package (WLP) technology using anisotropic conductive films (ACFs) and flex substrates, an innovative packaging technology that requires fewer process steps and lower process temperature, and also provides flexible packages. This study demonstrated and evaluated the reliability of flexible packages that consisted of a flexible Chip-on-Flex (COF) assembly and embedded Chip-in-Flex (CIF) packages by applying a WLP process.The WLP process was successfully performed for the cases of void-free ACF lamination on a 50 μm thin wafer, wafer dicing without ACF delamination, and a flip-chip assembly which showed stable bump contact resistances. The fabricated COF assembly was more flexible than the conventional COF whose chip thickness is about 700 μm. To evaluate the flexibility of the COF assembly, a static bending test was performed under different bending radiuses: 35 mm, 30 mm, 25 mm, and 20 mm. Adopting optimized bonding processes of COF assembly and Flex-on-Flex (FOF) assembly, CIF packages were then successfully fabricated. The reliability of the CIF packages was evaluated via a high temperature/humidity test (85 °C/85% RH) and high temperature storage test (HTST). From the reliability test results, the CIF packages showed excellent 85 °C/85% RH reliability. Furthermore, guideline of ACF material property was suggested by Finite Element Analysis (FEA) for better HTST reliability.     

Leakage reduction through optimization of regular layout parameters

Regular layouts that follow restrictive design rules are essential to robust CMOS design in order to alleviate many manufacturing induced effects, such as the effect of non-rectangular gate (NRG) due to sub-wavelength lithograph. NRG dramatically increases the leakage current by more than 15X compared to that of ideal physical layout. To mitigate such a penalty, we developed a technique to optimize regular layout through restrictive design rule parameters and to benchmark post-lithography circuit performance. We propose a procedure to systematically optimize key layout parameters in regular layout to minimize the leakage energy with minimal over head to active energy, circuit speed and area. The proposed layout optimization technique is demonstrated with a 65 nm technology and projected for 45 nm and 32 nm technology nodes. Experimental results show that more than 70% reduction in leakage can be achieved with area penalty of ～10% and 9–12% overhead on circuit speed and active energy.     

Chemically deposited ZnS thin film as potential X-ray radiation sensor

In this article X-ray radiation sensitivity of ZnS thin film prepared by a chemical bath deposition technique has been reported. The films were prepared under 0.10, 0.15 and 0.20 molarity (M). Characterization reports show that the 0.20 M film has the best quality than the other low molarity films. I-V characteristics of the films were studied under dark condition and observed that the film prepared at 0.20 M has an electrical conductivity of 2.06×10⁻⁶ (Ω cm)⁻¹ which is about 10 times greater than the other lower molarity films. Further, the I-V characteristic of this film has studied under UV and X-ray radiations. The current under X-ray radiation is found to be significantly higher than that under the UV radiation. At a fix bias voltage of 1.0 V, the conductivity under UV radiation is found to be 3.26×10⁻⁶ (Ω cm)⁻¹ whereas that under the X-ray is 4.13×10⁻⁵ (Ω cm)⁻¹. The sensitivity under X-ray radiation is significantly greater than that under the UV radiation. This analysis suggests that the ZnS thin film which is used as a UV radiation sensor can also be used as a potential X-ray radiation sensor.     

Thermal stability of melt grown Tl-doped PbTeSe material for thermoelectric applications

Although the thermoelectric performance of PbTe-based materials, processed by hot-pressing, has recently been improved, there are concerns about its thermal stability. On the other hand, during the process of melt crystal growth the material is formed in a quasi-equilibrium condition, which results in homogeneous solid structure in a lower-energy state and, consequently, more thermally stable and mechanically robust. To test the thermal stability of the melt-grown crystal, a Tl-doped PbTe_0.85 Se_0.15 ingot has been grown from the melt by directional solidification. Four adjacent disc-shape samples were sliced perpendicular to the growth axis from the grown boule. The thermoelectric characterizations together with microstructure examination and mechanical hardness measurements were performed on each of the three as-grown samples as well as on the fourth sample after it has been annealed at 455 °C for 570 h. The characterization results, showing that the annealing has essentially no effects on the thermoelectric properties, metallurgical microstructure as well as mechanical hardness of the annealed sample, have demonstrated that structurally homogeneous materials processed by melt growth are more suitable than those processed by other methods, such as hot press or quench-annealing, for long-term thermoelectric applications at elevated temperatures.     

The effect of oxide layer thickness on the quantification of 1.5 MeV γ–radiation induced interface traps in the Ag/SiO2/Si MOS devices

This work presents the effect of varied thickness of oxide layer and radiation dose on electrical characteristics of Ag/SiO₂/Si MOS devices irradiated by 1.5 MeV γ–radiations of varied doses. SiO₂ layers of 50, 100, 150 and 200 nm thickness were grown on Si substrates using dry oxidation and exposed to radiation doses of 1, 10 and 100 kGy. The exposure to radiation resulted in generation of fixed charge centers and interface traps in the SiO₂ and at the Si/SiO₂ interface. Capacitance-conductance-voltage (C-G-V) and capacitance-conductance-frequency (C-G-f) measurements were performed at room temperature for all MOS devices to quantify the active traps and their lifetimes. It is shown that accumulation and minimum capacitances decreased as the thickness of SiO₂ layer increased. For the unexposed MOS devices, the flat band voltage V_FB decreased at a rate of −0.12 V/nm, density of active traps increased by 4.5 times and depletion capacitance C_DP, increased by 2.5 times with the increase of oxide layer thickness from 50 to 200 nm. The density of active traps showed strong dependence on the frequency of the applied signal and the thickness of the oxide layer. The MOS device with 200 nm thick oxide layer irradiated with 100 kGy showed density of active interface traps was high at 50 kHz and was 3.6×10¹⁰ eV⁻¹ cm⁻². The relaxation time of the interface traps also increased with the exposure of γ–radiation and reached to 9.8 µs at 32 kHz in 200 nm thick oxide MOS device exposed with a dose of 100 kGy. It was inferred that this was due to formation of continuum energy states within the band gap and activation of these defects depended on the thickness of oxide layer, applied reverse bias and the working frequency. The present study highlighted the role of thickness of oxide layer in radiation hard environments and that only at high frequency, radiation induced traps remain passivated due to long relaxation times.     

Design of implantable CPW fed monopole H-slot antenna for 2.45 GHz ISM band applications

In this paper, the design and radiation performance of the novel miniature implantable coplanar waveguide fed H-slot antenna for embedded in human body operating in the ISM band frequency is proposed. A parametric model of a skin, fat and muscle implantable antenna is designed and a prototype is fabricated on biocompatible alumina ceramic substrate (ɛ_r = 9.8 and thickness = 0.65 mm) and it is tested. Antennas are further analyzed in inside a pork tissue and human body phantom liquid. Results indicate strong dependence of the exhibited radiation performance (radiation pattern, gain, specific absorption rate and quality of communication with exterior instruments) on design parameters and operating frequency. The proposed antenna design methodology can be applied to optimize antenna for several implantation scenarios and ISM band applications.     

Characterization of TiAl alloy films for potential application in MEMS bimorph actuators

In this letter, we demonstrate the feasibility of applying TiAl alloy film for the fabrication of bimorph actuators. The TiAl alloy films were prepared by thermal annealing at 400°C of Ti/Al multilayers, which were deposited by DC magnetron sputtering from Ti and Al targets. The microstructure and surface morphology of TiAl alloy films were analyzed by X-ray diffraction and scanning electron microscopy, which showed that TiAl alloy film is formed in the mixed phases of TiAl₃ and Ti₃₆Al₆₄, depending on the deposition conditions. The resistivity of TiAl film is about 9 μΩ cm, and the stress is about 200 MPa. Our nano-indentation measurements showed that the Young's modulus and hardness of TiAl alloy films are 175 and 6.5 GPa, respectively, which are larger than that of Al and comparable to Si. We have successfully fabricated the bimorph actuators based on the TiAl alloy films and our test cantilevers up to 500 μm long showed very straight with tip bending as small as ±5 μm, indicating negligible stress gradient in TiAl film. Our preliminary testing results indicated that TiAl alloy film has potential application for bimorph actuators.     

Rail to rail radiation hardened operational amplifier in standard CMOS technology with standard layout techniques

This work presents a rail-to-rail operational amplifier hardened by design against ionizing radiation at circuit level, using only standard layout techniques. Not changing transistor layout, for instance by using enclosed layout structures, allows design and simulation using the standard models provided by the foundry. The circuit was fabricated on a standard 0.35 μm CMOS process, and submitted to a total ionizing dose (TID) test campaign using a ⁶⁰Co radiation source, at a dose rate of 0.5 rad(Si)/s, reaching a final accumulated dose of 500 krad(Si). The circuit proved to be radiation tolerant for the tested accumulated dose. The design practices used to mitigate TID effects are presented and discussed in detail.     

Reliability of high voltage/high power L/S-band Hbt technology

This paper presents the qualification methodology and results of an InGaP HBT process industrialised by UMS to cover high power L and S band applications. The high level of robustness of the technology has been demonstrated with RF test up to 9 dB compression without any degradation. MTTF of 12 FIT/mm² of semiconductor at a junction temperature of 175 °C have been demonstrated based on more than 560,000 component hours. Also, following the activation period, an asymptotic decrease of the Beta is pointed out both at WLR and long term reliability test and modelled by a Black law. Activation energy between 0.52 and 0.75 eV and a Black factor between 1 and 2 was found. An original and complete failure analysis methodology including NIR emission microscopy, FIB and TEM analysis, have been used to characterised infant mortality for which the root cause is attributed to the propagation through the base–emitter junction of dislocation in the epitaxy. Activation energy of 0.58 eV was determined for this mechanism.