Search

We examine the characteristics of a 4-stage nested Mach-Zehnder interferometer optical switch with phase generating couplers, and demonstrate that crosstalk is suppressed to less than -40 dB over 200nm wavelength range from 1450 to 1650 nm by choosing six ports among 16 output ports.

A design method for broadband metasurfaces is presented based on the transmission-line (TL) theory. A simple non-resonant one-dimensional (1-D) TL model is introduced to the design of metasurfaces for refracting a normally incident plane wave to other angles from normal, and the theoretical formula for uniquely determining the line length of the TL is shown. As an example, a metasurface with a refraction angle of $\pi /9$ radians is designed with the 1-D TL model. In additions, the validity of the design method and the broadband operations are demonstrated by circuit simulations with a SPICE simulator.

We examined light propagation along the spot size converter of silicon photonic wire waveguides, and show there are two maxima in coupling efficiency. An optimal design was given in terms of compactness and high efficiency by changing its dimension and shape.

Two-dimensional (2-D) full-tensor anisotropic metamaterials with the impedance of free space are presented based on the theory of the 2-D distributed transmission-line models. A method for determining the structural parameters is shown through a design of a beam shifter based on transformation electromagnetics to translate incident plane waves according to the coordinate system transformed from the original one. In addition, the broadband operations of the beam shifter for electromagnetic waves propagating in free space are numerically demonstrated by full-wave simulations.

A design method for negative refractive index (NRI) metamaterials is proposed based on the transmission-line (TL) approach. A distributed TL model is introduced to the design and the design formulas are shown. A NRI lens operating at 3.85 GHz is designed with the model as an example. The operation and the validity of the design method are exhibited from the calculated results by circuit simulations with a SPICE simulator.

Equivalent circuit models for two-dimensional (2-D) full-tensor anisotropic composite right/left-handed metamaterials are presented to design NRI metamaterials based on transformation electromagnetics for manipulating backword waves according to the transformed coordinate system. Relations of circuit parameters and material parameters are shown by comparing circuit equations with Maxwell's equations. As an example, a 2-D full-tensor negative refractive index (NRI) lens based on transformation electromagnetics are designed by using the equivalent circuit models. The full-tensor NRI lens can shift positions of the focus and the refocus according to the coordinate system transformed from the original one embedding a general 2-D NRI lens. Its operations are shown by circuit simulations with a SPICE simulator.

We investigated the channeling implantation of dopant ions into 4H-SiC in detail. The advantages of channeling implantation were clarified by both experimental and Monte Carlo simulation. Extremely abrupt deep profile with box-like can be formed by channeling implantation of Al and P ions. In the case of B and N ions, retrograde-like profile can be obtained by channeling implantation. The unique dopant profile can be realized by channeling implantation. Both vertical and lateral straggling becomes small by using channeling implantation for Al ions. This technique should contribute to improving the device performance such as gate pitch scaling and low specific on-resistance.

A design method for two-dimensional (2-D) zero-index materials (ZIMs) is presented based on the transmission-line (TL) approach in order to realize invisible cloaks for hiding objects. A simple 2-D distributed TL model is proposed and the formula to calculate the dispersion characteristics is theoretically derived. It is shown from the calculated dispersion characteristics that a Dirac cone is always formed at the T -point without adjustments of the unit cell for the degeneration of propagation modes and ZIMs can be easily designed with the proposed model. In addition, a ZIM operating at 5 GHz is designed with the proposed model, and its cloaking operations and the validity of the design theory are demonstrated by circuit simulations.

We extend the theory of equivalent circuit models for two-dimensional (2-D) full-tensor anisotropic electromagnetic metamaterials and introduce the design method with equivalent circuit models to designs of 2-D full-tensor anisotropic acoustic metamaterials. Relations of circuit parameters and material parameters including the off-diagonal components of the mass density tensor are revealed from the duality of circuit equations and acoustic equations. A 2D acoustic carpet cloak for hiding a bump on a flat surface is designed with equivalent circuit models to confirm the validity of the theory. Circuit simulations are carried out and the voltage distributions and the radar cross sections are compared with those for the cases with the flat surface and the bump. Those results show the angle independent cloaking operations of the designed acoustic carpet cloak.

In this study, we examined the effect of Si-ion irradiation on Rs of YBCO thin films. We measured Rs 90 and Rs0 of YBCO thin films in a magnetic field applied both normal and parallel to the film plane. Si-ion irradiation conditions were configured as follows: irradiation energy = 50–500 keV, irradiation ion density = 1–8 × 10 12 ion/ cm2. We found that the Rs90 decreased through ion irradiation, and Si-ion irradiation with an irradiation energy of 200 keV and an irradiated ion density of 4 × 1012 ion/cm2 being the most effective configuration for reducing Rs90 in high magnetic fields. Magnetic field-dependent Rs0 was quite small for all YBCO films with and without ion irradiation. When a magnetic field is applied parallel to the film plane, the blocking layers of the YBCO act as strong pins, therefore, R s0 in the magnetic field is small without introduction of artificial pins. However, we found that the Rs0 of YBCO films became small with Si-ion irradiation than that of the YBCO film without Si-ion irradiation, that the condition of ion energy 200 keV and ion irradiation density 1 × 10 12 ion/cm2 could reduce Rs0 most.

We demonstrate a $1 \times \mathrm {N}$ nested Mach-Zehnder interferometer optical switch configuration with low crosstalk regardless of coupling ratio deviation. It also has an inherent symmetry which helps a scale expansion of its port count.

Reduction of the contact resistance at source/drain and metal electrodes is one of the key challenges in the fabrication of high performance CMOS devices. In recent years, several studies have addressed the issue of minimizing the specific contact resistivity (ρ c ) [1] – [5] . Quite low values of ρ c in the sub-10 −9 ohm-cm 2 region have been reported for advanced technologies.

We demonstrate broadband transmission-line illusions based on transformation electromagnetics at microwave frequencies by using the distributed full-tensor anisotropic medium. Due to an intrinsic nature of the non-resonant unit cell of the medium, the illusions operate from DC to an upper limit frequency where the homogeneous medium approximation holds. Two-dimensional groove and bump illusion media mimicking scattered waves by an original groove and a bump are designed. Their broadband and incident angle independent operations are confirmed by circuit simulations. The groove illusion medium is implemented on a dielectric substrate with microstrip-line technology, and it is confirmed experimentally by near-field measurements that the illusion medium well mimics scattered waves by the original groove in the broadband frequency range from 2.60 GHz to 4.65 GHz.

Planar distributed full-tensor anisotropic metamaterials for cloaks of invisibility based on transformation electromagnetics are proposed. The proposed metamaterials are composed of nonresonant transmission lines and are advantageous in full control of the off-diagonal components of the permeability tensor as well as broadband and low-loss characteristics. The explicit design formulas for the metamaterials are given based on the equivalent circuit derived directly from Maxwell's equations. A carpet cloak of invisibility is designed and the validity of the design theory is confirmed by circuit simulations. In addition, the carpet cloak is implemented in microstrip line technology and its performance is demonstrated experimentally at microwave frequencies.

We propose a novel hyperbolic coordinate transformation for cylindrical invisibility cloaks based on the transformation electromagnetics. It is mathematically shown that the cloak with the proposed transformation can be implemented by a medium with a position independent permeability, which potentially leads to wideband and low loss operations with easy implementations at microwave or higher frequency regions. A transmission-type cloak is designed and the required permittivity and permeability are calculated. We demonstrate the operation of the cylindrical cloak based on the circuit theory and the validity of the proposed concept is shown by comparing the radar cross section of the cloak with that of a conventional one.

A concept of a flat retroreflector mimicking a cylindrical retroreflector with a function of a Luneburg lens is presented based on the transformation electromagnetics. The retroreflector has retroreflection characteristics even through the mirror surface is flat, and operates with wide incident angles. The retroreflector is designed with equivalent circuit models of full-tensor anisotropic metamaterials. Circuit simulations are carried out with a SPICE simulator in order to confirm the validity of the design and the operations. Simulation results show theoretically the retroreflection operations with wide incident angles and the validity of the concept.

We studied N+/P junction formation in germanium by various ion species systematically. We evaluated the effect of co-implantation of C, Al and Sn in detail. It should be emphasized that the trade-off relationship between Rs and Xj can be overcome by Sn co-implantation, although a slight increase in Rs value was observed. Diffusion of phosphorus can be controlled by Sn co-implantation technique. We also evaluated the residual defects and stress generation of Sn co-implantation.

Carbon and hydrocarbon gettering effects for alkali dopant from factory environment and other heavy metal are investigated. The gettering layers are produced by C 3 H 5 , C 7 H 7 and C monomer implantation. Potassium is concentrated to the gettering layer region after annealing. The gettering effect for potassium is increasing with increase the hydrocarbon cluster size. However, carbon gettering effects for magnesium and sodium are not dominant. In addition, Molybdenum and tungsten diffuse only a little, so the carbon gettering effects are small. The gettering effect by hydrocarbon cluster dopant for potassium is effective.

Recently, even a small cube satellite carries a Ku-band transponder and, then, its reception system is required in an earth radio station. A local oscillator (LO) frequency is so high that control and management of the frequency and phase becomes a big issue. We propose optoelectronic frequency conversion using an electro-absorption modulated laser, where LO-on-fiber and IF-on-fiber is transmitted as uplink and downlink, respectively, in a single fiber. The electro-absorption modulator functions as a photodiode to the uplink LO-on-fiber signal as well as the light modulator to convert radio frequency subcarrier in this system.

As a novel application based on the transformation electromagnetics, a flat focusing reflector is presented. This reflector mimics a conventional parabolic reflector, and the reflected waves can be focused at a point even through the mirror surface is flat. By employing equivalent circuit models of the distributed full-tensor anisotropic metamaterials, the flat focusing reflector is designed and its operations are analyzed by circuit simulations.

Silicon semiconductor devices have remarkably been improved by the process scaling and introduction of some boosting technologies such as high-k/metal gate and strained silicon. However further improvement is quite difficult from the view point of mobility of silicon material. To overcome this problem, an increasing amount of attention has been devoted to the investigation of some higher carrier mobility materials such as SiGe, Ge or III-V materials. Among those materials, due to higher carrier mobility of Ge, it is promising as one of the candidates for high-performance devices with low-power and high-speed operation [1]. However several challenges still remain for the fabrication of Ge MOSFETs. For junction formation, it is difficult to form shallow N+/P junction in Ge due to the anomalous high diffusion coefficient of donor ions. On the other hand, forming shallow P+/N junction is relatively easy, however the high activation is difficult. To address these problems, some processes have been proposed such as aluminum doping [2], group-III metal doping [3] and optimization of Flash Lamp Annealing (FLA) [4]. In this study, we focused on the effect of oxygen remaining in the surface region of Ge substrate. Generally, a large amount of solid-solved oxygen is contained in Ge substrate. It is known that the oxygen inside Ge crystal acts as a Thermal Double Donor (TDD) [5]. TDD will inhibit the activation of acceptor ions in Ge and result in increase in the sheet resistance (Rs) of p+ diffusion layer formed into the surface region of the Ge substrate. In order to improve the activation, the Ge substrate is pre-heated at high temperature in the vacuum chamber before ion implantation to control the oxygen concentration in the surface region. Oxygen atoms in the Ge substrate can easily out-diffuse at the initial stage of ion implantation. Furthermore implantation is carried out at relatively low temperature to avoid TED of boron. In this paper, we report the results of BF 2 implantation into Ge substrate with pre-heating process.

An optical switch that routes optical signals without converting them into electrical signals is a key component used in optical fiber communications. It is required to exhibit low loss, low crosstalk, and low power consumption. A 1 × N arrayed-waveguide optical switch has an advantage whose circuit size is small. In a design of the 1 × N arrayed-waveguide optical switch, we employ some window functions other than a conventional Gaussian distribution. We show that slight modification of the optical power ratio between the arrayed-waveguides effectively suppresses the crosstalk to unrouted output ports.

A flat reflector having retroreflection characteristics is presented based on transformation electromagnetics. The retroreflector is designed with a distributed full-tensor anisotropic metamaterial. Its retroreflection operations are confirmed by circuit simulations based on the equivalent circuit model of the distributed anisotropic metamaterial.

Donor and acceptor impurities mainly focused on aluminum and phosphorus implanted Germanium has been characterized in terms of mainly diffusion behaviors and carrier activations. Among Group III elements, aluminum implanted sample shows shallower junction and lower sheet resistance. No diffusion occurs under annealing conditions performed in the experiment (up to RTA 700oC 30sec). The co-existence of acceptor and donor impurities influences the diffusion and activation behaviors of mutual impurities. Aluminum co-implanted with phosphorus compensates carrier concentration, and retards the phosphorus diffusion.

In this paper, we report on the formation of shallow junctions with high activation in both n+/p and p+/n Ge junctions using ion implantation and Flash Lamp Annealing (FLA). The shallowest junction depths formed for the n+/p and p+/n junctions were 9.5 nm and 10.7 nm with sheet resistances of 620 ohms/sq. and 414 ohms/sq., respectively. Additionally, by reducing knocked-on oxygen during ion implantation, the sheet resistance was decreased by 5 to 15%. The lowest sheet resistance was 235 ohms/sq. with a junction depth of 21.5 nm in the n+/p Ge. These results indicate that the potential for forming ultra-shallow n+/p and p+/n junctions in the nanometer range in Ge devices using FLA is very high, leading to realistic monolithically-integrated Ge CMOS devices.

2-D coordinate transformation resonators based on transformation electromagnetics are proposed. The proposed resonators are with the shapes and effective media parameters coordinate transformed from arbitrary different shaped resonators. The resonant modes including higher order modes are determined not by physical shapes of the resonators but by shapes, media parameters, and boundary conditions of their original resonators. Proposed coordinate transformation resonators are designed and implemented on a dielectric substrate with microstrip-line technology using the distributed full-tensor anisotropic metamaterials. It is experimentally confirmed that resonant characteristics of the implemented resonators are determined by dimensions and boundary conditions of original resonators and the unloaded Q-factors hardly depend on the coordinate transformation.

Newly developed sweep beam Cluster ion implanter: CLARIS with 0.2-7keV energy range for Boron beam and 1-10keV energy range for Carbon beam is introduced. Novel Cluster ion implantation technology is capable for 45nm beyond device requiring USJ formation (70%) and low sheet resistivity (

A decaborane implantation system has been developed. The maximum beam current achieved at a wafer is 30 μA at 5 keV with the divergence less than 0.4°, which corresponds to the equivalent 500 eV–300 μA boron monomer implantation without an energy contamination. As-implanted secondary ion mass spectroscopy (SIMS) profile of the decaborane implanted at the equivalent energy 500 eV shows the steeper and shallower profile than that of the boron implanted. The result of R s – X j proves the higher activation with shallower junction depth. These advantages possibly arise from the self-amorphization layer by the decaborane implantation.

In this study, we investigated an ion implantation effect to change the physical property of High Purity Semi-Insulating Silicon Carbide (HPSI-SiC) wafers. Ion implanter IMPHEAT® was used to implant an ion beam into SiC wafers. The spectroscopic analysis was carried out before and after ion implantation. The chucking force was also measured before and after ion implantation to confirm change of the force. Additionally, the implant depth profile was investigated with the effect of a Plasma Flood Gun (PFG).

A carpet cloak of invisibility for sinusoidal periodic boundaries to mimic a specular flat floor is introduced. The material parameters are derived based on a non-conformal coordinate transformation, and a carpet cloak is designed and implemented based on the transmission line metamaterials concept with an equivalent circuit model. Wideband specular reflection operations of the carpet cloak are confirmed by circuit simulations.

Enhancement of transistor drivability with suppressing short channel effect is a mandatory requirement for device scaling. In order to address the requirement, transistor structure transition from 2D bulk planar to SOI or 3D FinFET structures is now proceeding[1-3]. In FinFET structures, high dose tilt implantations are used in source drain extension formation. This implantations cause amorphization of Si fins, and there exists an issue here for difficulty in regrowth of amorphized Si fins during successive activation annealing. For further scaling, fin width becomes narrower, and regrowth from crystal channel also cannot be much expected. Amorphized Si fin cannot be easily regrown to Si fin top during activation annealing, resulting in twin formation and/or poly crystal[4] as shown in the schematic figure (Fig.1). In addition, memory devices also have almost the same transistor structure. Shrinking active Si areas in transistors of flash memory embedded in surrounding STI oxide is similar structure as tall Si fin in FinFET structures. Doping with ion implantation causes narrow active Si areas amorphous, and regrowth to the active Si top is also becoming difficult. Doping without Si amorphization is a challenge for further scaling of transistors both in logic devices and memory devices. This paper reports high dose doping by using implantation to heated Si substrates. Crystalline quality, depth profiles and resistance of As+, P+ and BF2+ implanted Si at elevated temperatures have been investigated. It will be shown that high dose doping without amorphization, and also low resistance of implanted regions after annealing can be successfully embodied.

A physical equivalent circuit model for 2D full-tensor anisotropic materials is presented. From the circuit analysis, it is shown that the diagonal components of the permeability tensor directly correspond to the self inductances per unit length, and the off-diagonal components physically correspond to the mutual inductance per unit length. A 2D carpet cloak is designed and its operation is confirmed with circuit simulations. The complex voltage distributions agree well with those of corresponding specular reflection cases, and validity and usefulness of the proposed equivalent circuit are confirmed.

We compared BF 2 , In, Ga, C+Ga and In+BF 2 dopant species for nMOS HALO at 22nm node for planar bulk & PD-SOI or for FD-SOI ground plane back-gate doping which require steep retrograde dopant profile and good dopant activation using a 1200°C Flash + 900°C 10 sec RTA anneal sequence. The best results were with the C+Ga co-implant realizing a steep surface dopant profile and dopant activation in the 2–3E18/cm3 level. In dopant activation was limited to 3–7E13/cm3 due to low solid solubility limit from the 900°C RTA anneal. The BF 2 , In+BF 2 and Ga implant conditions all showed flat to increasing dopant profile pile-up at the surface which is not desirable.

For 28nm and beyond technology nodes it is essential to enhance carrier mobility of the devices by introducing embedded Si:C structures using new materials or structures or new implant and anneal process schemes. In this article we review and verify available information using Si:C formation through implant and anneal approach with low temperature cluster carbon and cluster phosphorous implants. We show here the difference in process results for single and double carbon implants for various pre-anneal and laser annealing conditions. This article explores the effect of cluster carbon implants on various pre-anneal conditions and implant temperature effects on sheet resistance, carbon substitution and junction depths which are critical in determining important device characteristics.