bluuebunny/crossref_metadata_2025 huggingface dataset:
USJ Dopant Bleaching and Device Effects in Advanced Microelectronic Plasma Enhanced Resist Strip Processing
Authors: Wirbeleit Frank , Grimm Volker , Krüger Christian , Streck Christoph , Sonnemans Roger , Berry Ivan
Published: April 2011

The impact of low temperature plasma resist strip on doped silicon surface and microelectronic device performance is investigated using different chemical gas mixtures. In this investigation, different plasma treatments where applied on non-structured and structured silicon on insulator (SOI) wafers post ultra shallow surface implants .The main surface impacts dopant bleaching and oxide loss in conjunction with plasma enhanced re-oxidation are analyzed by time of flight secondary ion mass spectrometry (TOF-SIMS) and electrical measurements of microelectronic test devices. As the result, a long range plasma radiation induced dopant activation and deactivation is separated as the main effect from surface oxide loss and re-oxidation processes. This implies further optimization of plasma resist strip processes for device improvements.
Ion implantation for low-resistive source/drain contacts in FinFET devices
Authors: van Dal Mark J. H. , Duffy Ray , Pawlak Bartek J. , Collaert Nadine , Jurczak Malgorzata , Lander Robert J. P.
Published: April 2011

FinFET is one of the leading candidates to replace the classical planar MOSFET for future CMOS technologies due to the double-gate configuration of the device leading to an intrinsically superior short channel effect (SCE) control. A major challenge for FinFETs is the increase in parasitic source-drain resistance (Rsd) as the fin width is scaled. As fins must be narrow in order to control SCEs, Rsd reduction is critical. This work will deal with the challenges faced in the use of ion implantation for the low-ohmic source-drain contacts. Firstly a new technique to characterize fin sidewall doping concentration will be introduced. We will have a closer look at the Rsd dependency upon fin width for different fin implant conditions and investigate how the implant conditions affect FinFET device performance. It will be shown that the cause of the device degradation upon fin width scaling is related to the fundamental issues of silicon crystal integrity in thin-body Si after amorphizing implant and recrystallization during source-drain activation.
Pt Segregation at the NiSi/Si Interface and a Relationship with the Microstructure of NiSi
Authors: Akutsu Haruko , Itokawa Hiroshi , Nakamura Kazuhiko , Iinuma Toshihiko , Suguro Kyoichi , Uchida Hiroshi , Tada Masanori
Published: April 2011

Nickel monosilicide (NiSi) is used for lowering the parasitic resistances in source/drain. However, NiSi has a disadvantage of lower thermal instability such as NiSi2 nucleation and agglomeration. We first reported Pt segregation was found at a NiSi/Si interface by Atom Probe (AP) analysis.[6] In this study, we found that the scheme of Ni silicide grain growth and the resultant NiSi crystal shape is strongly affected by the existence of Pt by utilizing AP analysis, TEM and FE-SEM. AP observations were carried on a Ni-Pt as sputterd sample and on a Ni-Pt as annealed sample. The depth profile for the sample after silicidation indicates Pt atoms are segregated at a NiSi surface and NiSi/Si interface. For the analysis of the Pt distribution in the sample after silicidation in more details, we thoroughly analyzed the 3D image as follows: a cylindrical part is extracted from the 3D image; it is divided into 5nm thick slices; and 2D images depicting density-distribution of Pt and As. From these 2D images, we found Pt atoms exist around NiSi grains. The Atom Probe result indicates that Pt atoms segregate at the NiSi surface, grain boundaries and NiSi/Si interface. Plane view TEM and FE-SEM observations were carried out on Ni(Pt) silicide and on Ni silicide without Pt to find the influence of the segregated Pt atoms on the microstructure of NiSi. The spindle shape of NiSi(w/o Pt) grains were observed on the former. On the other hand, we observed on the latter that the Pt addition affected the shape of the NiSi grains and changed NiSi grains to round polygonal shape and the average grain size became smaller. It can be said that the Pt addition suppresses a crystal growth along in a longitudinal direction of a grain. We speculate that fine round shape NiSi grains are formed as a result of the suppression of the anisotropic crystal growth by Pt segregation, and provide the improvement of the thermal stability of the NiSi film.
A Comprehensive Atomistic Kinetic Monte Carlo Model for Amorphization/Recrystallization and its Effects on Dopants
Authors: Zographos Nikolas , Martin-Bragado Ignacio
Published: April 2011

This work shows a comprehensive atomistic model to describe amorphization and recrystallization, and its different effects on dopants in silicon. We begin by describing the physical basis of the model used, based on the transformation of ion-implanted dopants and generated point defects into amorphous pockets of different sizes. The growth and dissolution of amorphous pockets is simulated by the capture and recombination of point defects with different activation energies. In some cases, this growth leads to the formation of amorphous layers. These layers, composed of a set of amorphous elements, have an activation energy to be recrystallized. The recrystallization velocity is modeled not only depending on temperature, but also on dopant concentration. During the recrystallization, dopants move with the recrystallization front to simulate the dopant redistribution during solid phase epitaxial regrowth (SPER). At the edge of the amorphous-crystalline interface, the remaining damage forms end-of-range (EOR) defects.

Once the model is explained, we discuss the calibration methodology used to reproduce several amorphous/crystalline (A/C) experiments, including the dependencies of the A/C transition temperature on dose rate and ion mass, and the A/C depth on ion implant energy.

This calibrated model allows us to explore the redistribution of several dopants, including B, As, F, and In, during SPER. Experimental results for all these dopants are compared with relevant simulations.
Modelling of Sb Activation in Ultra-shallow Junction Regions in Bulk and Strained Si
Authors: Lai Yan , Cordero Nicolas , Greer James C
Published: April 2011

The activation behaviour of dopants in ultra-shallow junctions on strained silicon is investigated from a simulation vantage point. Process models available in commercial simulation tools are typically developed for junctions formed with high implantation energies (> 50 keV) and for long anneal times. Hence the question arises as to whether these models and parameter sets can accurately predict the active profile for highly doped, ultra-shallow junctions formed thin strained silicon layers using short rapid thermal anneals (RTA, <10 seconds) at temperatures below 800 °C. By incorporating the results from experimental data, we develop modified models allowing for improved predictions of antimony activation within both bulk and strained silicon.
Modeling of Effect of Stress on C Diffusion/Clustering in Si
Authors: Guo Hsiu-Wu , Ahn Chihak , Dunham Scott T
Published: April 2011

Extensive ab-initio calculations were performed to find formation energies of stable C complex configurations in silicon as function of stress. The results indicate that substitutional C is the lowest energy state, while the <100> split interstitial is the dominant mobile species. Investigation of small carbon/interstitial clustering suggests that these clusters are only significant under a substantial interstitial supersaturation. We studied the diffusion path for neutral C including the impact of stress. Through KLMC analysis of stress effect on diffusivity, we found that tensile biaxial strain enhances the effective C diffusivity, with a stronger stress dependence for C diffusivity in the out-of-plane direction.
Atomistic Simulations of Epitaxial Regrowth of As-doped Silicon
Authors: Yoon Joo Chul , Dunham Scott
Published: April 2011

We conducted molecular dynamics (MD) simulations of solid phase epitaxial growth of As-doped Si using a Tersoff potential characterized via comparison to DFT calculations, including energies of AsnV clusters. The Si:As systems were initialized by amorphizing the surface region of crystalline silicon via Si ion implantation and/or selective melting. The remaining crystalline region provides dual function of controlling temperature in system without perturbing regrowth and providing seed for recrystallization. After recrystallization, isolated As atoms occupy substitutional sites, with the average number of nearest neighbors for As changing from about 3.3 in amorphous Si to 4 after crystallization. We observe V incorporation associated with high As concentrations. A small fraction of isolated As atoms have associated vacancies, while vacancies are incorporated in the majority of cases in which there are sites with two As neighbors. These observations are consistent with our previous model developed to explain kinetics of As shallow junction formation which assumed V incorporation at sites with 2 or more As nearest neighbors to account for experimental data.
Efficacy of Damage Annealing in Advanced Ultra-Shallow Junction Processing
Authors: Timans Paul J , Hu Yao Zhi , Gelpey Jeff , McCoy Steve , Lerch Wilfried , Paul Silke , Bolze Detlef , Kheyrandish Hamid
Published: April 2011

Low thermal budget annealing approaches, such as millisecond annealing or solid-phase epitaxy (SPE) of amorphized silicon, electrically activate implanted dopants while minimizing diffusion. However, it is also important to anneal damage to the crystal lattice in order to minimize junction leakage. Annealing experiments were performed on low-energy B implants into both crystalline silicon and into wafers pre-amorphized by Ge implantation. Some wafers also received As implants for halo-style doping, and in some cases the halo implants were pre-annealed at 1050°C before the B-doping. The B-implants were annealed by either SPE at 650°C, spike annealing at 1050°C, or by millisecond annealing with flash-assisted RTP™ (fRTP™) at temperatures between 1250°C and 1350°C. Residual damage was characterized by photoluminescence and non-contact junction leakage current measurements, which permit rapid assessment of damage removal efficacy. Damage from the heavy ions used for the halo and pre-amorphization implants dominates the defect annealing behaviour. The halo doping is the critical factor in determining junction leakage current. Millisecond annealing at high temperatures helps to minimize residual damage while limiting diffusion.
Ab-Initio Modeling of Arsenic Pile-Up and Deactivation at the Si/SiO2 Interface
Authors: Gupta Naveen , Windl Wolfgang
Published: April 2011

Two recent papers by Pei et al. and Steen et al. have shown that the observed pile-up of arsenic at Si/SiO2 interfaces surprisingly does not seem to involve point defects as a major factor, causes local distortions that strain the Si in the pile-up region locally, and that the segregated arsenic atoms are deep donors. In this paper, we use ab-initio modeling to study possible configurations for high As concentrations that may fulfill these criteria. We find for a simple model structure that As nearest neighbors become stable in Si in the vicinity of the interface. We also have stud-ied dopant deactivation using bulk-Si models. Even without invoking point defects explicitly and starting from a purely substitutional arrangement, we find that the energetically most favorable configurations are most stable in the neutral charge state, indicating that high enough concentra-tions of arsenic atoms make them electrically inactive and hence result in dopant dose loss.
Structural Evolution of Amorphous Ge2Sb2Te5 Thin Films in the Transition to the Crystalline Phase
Authors: De Bastiani Riccardo , Piro Alberto Maria , Grimaldi Maria Grazia , Rimini Emanuele , Baratta Giuseppe , Strazzulla Giovanni
Published: April 2011

The crystallization kinetics of as-deposited amorphous Ge2Sb2Te5 thin films has been measured by in situ time resolved reflectivity. X-ray diffraction and Raman scattering analyses of partially transformed samples allowed to correlate the evolution of the transition to the structural modification in the long and short range configuration. The experimental results evidenced that during the early stages of crystallization there is a reduction of Ge-Te tetrahedral bonds, characteristics of the Ge coordination in amorphous Ge2Sb2Te5 films.
Photoemission Study of Energy Band Alignment of Ge2Sb2Te5 and Common CMOS Materials
Authors: Fang Lina Wei-Wei , Pan Ji-Sheng , Lim Andy Eu-Jin , Lee Rinus Tek-Po , Li Minghua , Zhao Rong , Shi Luping , Chong Tow-Chong , Yeo Yee-Chia
Published: April 2011

We report the energy band alignment of Ge2Sb2Te5 and a variety of common complementary-metal-oxide-semiconductor (CMOS) compatible materials. These materials include silicon, silicon oxide, hafnium oxide, silicon nitride as well as nickel silicide. High-resolution X-ray photoelectron spectroscopy was employed as the main tool to obtain the core-level spectra, the valence band spectra, and the energy loss spectra. A precise determination of the valence band offsets of Ge2Sb2Te5 and the various materials were obtained. The conduction band offsets were then determined. The energy band line-ups of Ge2Sb2Te5 and these CMOS compatible materials were established.
Large Optical Transitions in Rewritable Digital Versatile Discs: An Interlayer Atomic Zipper in a SbTe Alloy
Authors: Tominaga Junji , Fons Paul , Shima Takayuki , Kuwahara Masashi , Suzuki Osamu , Kolobov Alexander
Published: April 2011

Chalcogenides, in particular germanium-antimony-tellurium (GeSbTe) and antimony-rich tellurium (R-SbTe) based alloys, are the most technologically significant alloys currently being applied to recordable optical storage as typified by rewritable digital versatile discs (DVD-RW), DVD random access memory, (DVD-RAM). The same alloys are also being applied to nonvolatile random access memory electrical memory in the form of phase change random access memory (PCRAM). In 2004, the phase transition mechanism of GeSbTe was first revealed, demonstrating that the amorphous state is not a random configurational network but is locally well-ordered with the crystalline to amorphous switching process being based upon Ge atoms moving between octahedral and tetrahedral symmetry positions. The kinetic barrier between these two states gives rise to the non-volatile nature of GeSbTe as a storage medium. In contrast, no theoretical analysis has been proposed for SbTe alloys because a Ge-free system. In this paper, the Sb2Te structure has been investigated using the local density approximation (LDA) using a plane-wave basis and compared with experimental results. The effect of external stress on the structure was also investigated. It was found that Sb2Te undergoes two phase-transitions at around 18 GPa (compressive) and −3 GPa (tensile). In the case of negative stress, the c-axis was found to expanded more than the other axes, giving rise a large refractive index change. We report on coherent (uniaxial) melting induced by the breaking a sigma bond between Sb2Te3 and Sb superlattices. We believe this to be the origin of the phase transition that induces a large change in physical properties.
Crystallization Characteristics Of Phase Change Nanoparticle Arrays Fabricated By Self-Assembly Based Lithography
Authors: Zhang Yuan , Raoux Simone , Krebs Daniel , Krupp Leslie E. , Topuria Teya , Jordan-Sweet Jean , Caldwell Marissa , Rice Philip , Milliron Delia J. , Wong H.-S. Philip
Published: April 2011

Phase change nanodot arrays were fabricated using self-assembly diblock copolymer template PS-b-PMMA (polystyrene-poly (methyl-methacrylate)) and studied by time resolved X-ray diffraction. The size of the nanodots was less than 15nm in diameter with 40nm spacing. This method is quite flexible regarding the patterned materials, and can be used on different substrates. The crystallization behavior of small scale phase change nanodot arrays was studied for different materials, such as Ge15Sb85, Ge2Sb2Te5 and Ag and In doped Sb2Te. It was found that the nanodots had higher crystallization temperatures compared to their corresponding blanket films and crystallized over a broader temperature range.
Interface-charge-coupled polarization response model of Pt-BaTiO3-ZnO-Pt heterojunctions: Physical parameters variation
Authors: Voora Venkata , Hofmann Tino , Kjerstad Ann , Brandt Matthias , Lorenz Michael , Grundmann Marius , Schubert Mathias
Published: April 2011

Heterojunctions composed of wurtzite-structure (piezoelectric) ZnO and perovskite-structure (ferroelectric) BaTiO3 are very interesting because of the coupling effects between the non-switchable ionic charge of wurtzite-structure and electrically switchable lattice charge of pervoskite structure at their common interface. In this paper we report the variations in the overall electrical properties of the ZnO-BaTiO3 heterostructure as a function of different physical attributes by using our previously reported physical model approach. This numerical model analysis helps us to prepare the samples by using pulsed laser deposition with specific electrical properties. This study is also useful for the future device applications.
Oxidation of NiSi and Ni(Pt)Si: Molecular vs. Atomic Oxygen
Authors: Manandhar Sudha , Copp Brian , Vamala Chiranjeevi , Kelber Jeffry
Published: April 2011

X-ray photoelectron spectroscopy (XPS) has been used to characterize the reactivities of clean, stoichiometric NiSi and Ni(Pt)Si films on n-doped Si(100) substrates in O2, and in O+O2 environments. In the presence of O+O2, NiSi and Ni(Pt)Si form Ni silicate and Pt silicate overlayers, respectively, with oxide/silicate overlayer thicknesses of 41(4) Å (NiSi) and 28(3) Å (Ni(Pt)Si) after 4.5x104 L exposure. Exposure to O2 yields, for each material, a ∼7(1) Å thick SiO2 overlayer without transition metal oxidation. O+O2 induces rapid Si oxidation, formation of metal-rich silicides, and then the kinetically-driven oxidation of Ni or Pt to form a silicate. This may pose significant processing problems in silicate removal and unwanted Ni diffusion into other areas of the device.
Tailoring Electrical Conductivity and Mechanism of Carrier Transport in Zinc Oxide with Embedded Ag Layer
Authors: Han Hauk , Theodore N D , Alford Terry
Published: April 2011

The effects of an embedded silver layer on the electrical properties of zinc oxide (ZnO) / silver (Ag)/ zinc oxide (ZnO) layered composite structures on polymer substrates have been investigated. We have engineered transparent conducting oxide structures with greatly improved conductivity. Electrical properties are correlated with Ag thickness. Film thicknesses were determined using Rutherford backscattering spectrometry. Hall effect, 4-point probe, and UV-Vis spectrophotometer analyses were used to characterize electrical and optical properties. The results show that carrier concentration, mobility, and conductivity increase with Ag thickness. Increasing Ag thickness from 8 to 14 nm enhances sheet resistance and resistivity by six orders of magnitude. We describe of the influence of Ag thickness on electrical properties of the ZnO/Ag/ZnO composite and propose a conduction mechanism for this system.
Humidity Sensing Property of Zinc Oxide Film Deposited by PLD
Authors: Dixit Shobhna , Dubey K. C. , Mishra K. P. , Srivastava Atul , Shukla R. K. , Srivastava Anchal
Published: April 2011

This paper reports structural, morphological, optical and humidity sensing characteristics of pulsed laser deposited ZnO film. The XRD pattern reveals amorphous structure of the film. Scanning electron micrograph indicates formation of ZnO rods in micron size. Transmission increases gradually in the UV-VIS region. For studying the humidity sensing characteristics of the film, base of a right angled isosceles glass prism has been coated. Chopped light from a polarized He-Ne laser incident on the entry face of the prism gets reflected from the base – film – humid air interfaces and then emergent light is collected by the detector placed in front of the exit face of the prism. The least change in relative humidity which could be measured using the present configuration is 1.06RH%. Further the film is annealed at 400°C for four hours and its humidity sensing behavior is investigated in the similar manner which now shows a reversed trend. The sensitivity to humidity has decreased and the least change which could be detected now is 1.16RH%.
Emission Wavelength Control of Si-rich SiOx MOSLED by Detuning Vapor Fluence and Plasma Power During PECVD Growth
Authors: Lai Bo-Han , Pai Yi-Hao , Liu Chi-Wee , Lin Gong-Ru
Published: April 2011

Photoluminescence (PL) intensity and wavelength control of Si-rich SiOx film and Si-rich SiOx based MOSLED achieved by detuning plasma power (RF power) during plasma-enhanced chemical vapor deposition (PECVD) growth is investigated. The peak of PL spectrum blue-shifts from 780 to 400 nm by modifying the RF power form 20 to 70 W during PECVD growth. The average sizes of Si nanocluster under RF power of 60 and 70W are 2.61 and 1.83 nm, respectively. The EL color of Si nanocrystal (nc-Si) based MOSLEDs can be tunable among orange-red, green and blue colors by growing the SiOx films with PECVD under different RF power. Under RF power from 50 to 70W, the turn-on voltage of nc-Si based MOSLEDs increases from 26 to 60 V, the optical power also increases from 1.6 W/cm2 to 9.7 W/cm2 and the power-current slope are 0.51, 3.24 and 62.92 mW/A, respectively.
Synthesis and Characterization of Monodispersed Rare-earth Ion Doped CeO2 Coated on SiO2 Spheres
Authors: Muralidharan Pandurangan , Jo Seung Hwan , Lee Hyun Wook , Kim Do Kyung
Published: April 2011

Core–shell microspheres of monodispersed SiO2 coated with rare-earth ion doped CeO2 (Eu3+ Sm3+ Dy3+) were prepared through a sol-gel method and followed by heat treatment at 800 °C for 4 h. XRD patterns revealed the crystal structures of the doped CeO2 coated on amorphous SiO2 sphere as a shell subsequent to heat treatment at 800 °C. SEM and TEM analysis indicated the microstructures of the coating and uniform size distributions of microspheres. Photoluminescence studies showed that the luminescent property had significant influence depending on different dopant ions and the thickness of the shell coated on SiO2 spheres.
Synthesis and Characterization on Fe-doped In2O3 Nanoparticles
Authors: Dussan-Devia Sandra , Singh Manoj K , Sharman G. L. , Katiyar R. S. , Rinaldi C
Published: April 2011

Pure and Fe-doped In2O3 nanocrystalline powder was synthesized using a solution chemistry route based on the Sol-Gel process, which is a simple and inexpensive technique and produces long-time stable stock solutions. The X-ray diffraction patterns revealed the formation of nanocrystalline particle size with well-crystallized cubic bixbyte structure. The average crystal size was calculated from XRD patterns using Debye-Scherrer's equation for the (222) peak and found to be 8 nm. This observation agrees well with the particle size estimated from transmission electron microscopy (TEM). The observed Raman peaks in the doped materials are shifted towards the lower frequency up to 15 cm−1 and we did not observed any additional new Raman modes with Fe doping. This clearly indicates that Fe ions are indeed occupying interstitial/substitutional sites in the host In2O3, in agreement with XPS measurements. Magnetic properties were studied using superconducting quantum interface device magnetometer (Quantum design MPMS XL-7). Preliminary magnetic measurement results suggest the incorporation of the dopants in the diamagnetic In2O3-host structure.
Synthesis of Cadmium and its Oxide Nanomaterials by Pulsed Laser Ablation in Aqueous Media
Authors: Singh Subhash Chandra , Swarnkar Rajkumar , Gopal Ram
Published: April 2011

Cadmium based oxide and hydroxide nanocomposites material is synthesized by pulsed laser ablation of cadmium metal in the double distilled water. A piece of cadmium metal, placed on the bottom of glass vessel containing double distilled water, was irradiated with 1064 nm of pulsed Nd:YAG laser operating at 35 mJ/pulse energy and 10 ns pulse width for 30 minutes. Colloidal solution of produced Nanoparticles is found stable for two days. Fine white colored powder is obtained after drying centrifuged solution. UV-visible absorption of colloidal solution, XRD, TGA, DTA and FTIR of the powder is used for the characterization of material. Possible mechanism of synthesis and hydroxide to oxide transition is discussed.
Improved Characterization of high-k Degradation with Vacuum C-AFM
Authors: Polspoel Wouter , Vandervorst Wilfried , Aguilera Lidia , Porti Marc , Nafria Montserrat , Aymerich Xavier
Published: April 2011

Local phenomena like trap assisted tunneling and oxide breakdown (BD) in new high-k gate oxides in advanced MOS devices hinder the acquisition of device requirements stated in the International Technology Roadmap for Semiconductors (ITRS). Conductive Atomic Force Microscopy (C-AFM) visualizes these local phenomena by measuring the local tunneling through the dielectric. In the first part of this work we show that the physical composition of surface protrusions, that are produced at sites electrically stressed with C-AFM and that distort the electrical measurements, is oxidized Si. In the second part, we illustrate that C-AFM measurements become more reliable in high vacuum (1e−5torr) as surface (oxidized Si protrusions) and tip damage is reduced. Finally, we illustrate good agreement between conventional macroscopic electrical measurements and nanometer-scale C-AFM measurements on normal and gate – removed high-k capacitors, respectively. Moreover, to illustrate the strength of the local tunneling technique, we show the possibility of locating BD spots on a high-k capacitor.
The Road To Flexible Mems Integration
Authors: Witvrouw Ann
Published: April 2011

This paper first discusses the reasons for choosing CMOS-MEMS integration, in particular integration by poly-SiGe processing above CMOS. Next the current state-of-the-art for poly-SiGe MEMS integration and the needs for the future will be addressed. Market trends are translated into two roadmaps for MEMS integration. The first roadmap is based on existing poly-SiGe deposition processes at 400 − 450 ºC. The second roadmap explores processing techniques to lower the thermal budget and widen the application field of MEMS integration by using processing techniques such as metal-induced crystallization, laser annealing or self-assembly.
Effects of Sputtering Metal Deposition Parameters in the Photoresist used as a Sacrificial Layer in Micro-electromechanical System Devices
Authors: Molinero David
Published: April 2011

The present letter describes a reliability study of the micro-electromechanical system fabrication with a photoresist layer used as sacrificial layer with an aluminum beam deposited by means of RF sputtering method. This work reports changes of the roughness and planarity of the sacrificial layer beneath the aluminum film following the sputtering deposition. Such changes may be attributed to the alteration of the photoresist properties due principally to the outgassing of hydrogen by decomposition of C-H bonds under argon plasma. A safe deposition parameters area was identified where the photoresist layer keeps its properties and may be used as sacrificial layer.
Microstructured Soft Glass Fibers for Advanced Fiber Lasers
Authors: Schulzgen Axel , Li Li , Zhu Xiushan , Suzuki Shigeru , Temyanko Valery L. , Albert Jacques , Peyghambarian Nasser
Published: April 2011

Combining novel highly-doped phosphate glasses and advanced fiber drawing techniques, we fabricated and tested single-frequency fiber lasers that generate powers of more than 2-W. We demonstrate enhanced performance employing active photonic crystal fiber compared to more conventional devices that are based on large core step-index fiber.

Through the integration of phosphate glass fiber gratings and highly-doped active phosphate glass fiber, we improve on optical, thermal, and mechanical behavior of our compact fiber lasers. Powerful and widely tunable phosphate glass distributed fiber lasers are presented and the possibility of cascading several grating structure for multiple wavelength generation is demonstrated. We also present results on phase-locking and coherently combining the output of up to 37 fiber cores into a single, near-Gaussian laser beam. To achieve exclusive oscillation of the fundamental in-phase supermode, several all-fiber laser cavities have been designed, numerically analyzed, fabricated, and tested. We will report on a 10-cm long monolithic all-fiber laser that emits more than 12-W of optical power and is based on combining the output of 19 active cores. All the cores are integrated within the same cladding and arranged in a two-dimensional isometric array.
Single Carrier Initiated Low Excess Noise Mid-Wavelength Infrared Avalanche Photodiode using InAs-GaSb Strained Layer Superlattice
Authors: Banerjee Koushik , Mallick Shubhrangshu , Ghosh Siddhartha , Plis Elena , Rodriguez Jean Baptiste , Krishna Sanjay , Grein Christoph
Published: April 2011

Mid-wavelength infrared (MWIR) avalanche photodiodes (APDs) were fabricated using Indium Arsenide- Gallium Antimonide (InAs-GaSb) based strain layer superlattice (SLS) structures. They were engineered specifically to have either electron or hole dominated ionization. The gain characteristics and the excess noise factors were measured for both devices. The electron dominated p+-n−-n APD with a cut-off wavelength of 4.13 μm at 77 K had a maximum multiplication gain of 1800 measured at -20 V while that of the hole dominated n+-p--p structure with a cut-off wavelength of 4.98 μm at 77 K was 21.1 at -5 V at 77 K. Excess noise factors were measured between 1-1.2 up to a gain of 800 and between 1-1.18 up to a gain of 7 for electron and hole dominated APDs respectively.
ALADIN Doppler Wind Lidar and Related Programs at EADS Astrium
Authors: Morancais Didier , Fabre Frédéric , Toulemont Yves
Published: April 2011

The Atmospheric Laser Doppler Instrument (ALADIN) is the payload of the ADM-AEOLUS mission, which will make direct measurements of global wind fields. It will determine the wind velocity component normal to the satellite velocity vector. The instrument is a direct detection Doppler Lidar operating in the UV, which will be the first of its kind in space.

ALADIN is now in its final construction stage: the integration of the Flight Model is on-going. Most of the subsystems have been integrated; the payload performance and qualification test campaign will commence.

This paper describes the ALADIN the development status and the results obtained at this stage. This regards the receiver performance, the telescope development and the challenges of the laser.

The paper will also provide insights on the ATLID instrument design which is the backscatter lidar for the EarthCARE mission. This lidar program is starting its detailed design phase.

The ALADIN and ATLID instruments are developed by EADS Astrium Satellites for the European Space Agency.
Geospatial Remote Sensing Using Advanced Sensor Systems
Authors: Vaseashta Ashok
Published: April 2011

Recently, various nanoscale materials, devices, and systems with remarkable properties have been developed, with numerous unique applications in chem.-bio sensors, nanophotonics, and nanobiotechnology. This presentation covers satellite and aerial remote sensing science and methodologies employing nanotechnology based advanced sensor systems to improve performance, resolutions, and security. Increased demand on monitoring, surveillance due to global war on terrorism, weather prediction, and environmental pollution detection and monitoring have necessitated geospatial sensing with high accuracy, speed, and authenticity. Plasmonic interactions on the nanoscale and nanophotonics have produced new phenomena and technologies surpassing the realms of possibilities with conventional photonics and electronics. These new technologies could include high spatial resolution near-field imaging, high efficiency information processing and transferring, high capacity optical data storage, flexible- and high contrast displays, and precise detection, control and manipulation of nanoscale devices and integrated systems. Elements utilizing refractive or diffractive surfaces have found applications in novel sub-wavelength nanostructures satellites. The nanophotonics structures coupled with lightweight structures and advanced nanotechnology based sensors have resulted in launching of nano-satellites by several countries. The use of nanophotonics in space through the combination of micro, nano, integrated and fibre-optic technologies is to reduce susceptibility of the system to EMI, reduction in the weight of the signal cables (< 1/20 of electrical), higher information transmission capacity (GHz), reduced weight and volume, opto-isolation of critical spacecraft subsystems, high speed optical processing of RF and microwave signals, low propagation loss, and enhanced security encryption capabilities. Carbon Nanotubes (CNTs) based field emission electron gun (FEG) employ low voltage for emission and are actively researched as cold cathode microwave generation devices. CNTs based composites provide light-weight and compact platform with mechanical and thermal robustness. Such satellite system can be placed in low Earth orbit (LEO) to medium Earth orbit (MEO) as multi-sensor satellite imagers with panchromatic, multi-spectral, area and hyper spectral sensors on a single focal plane array (FPA), to achieve medium to high resolution (2.5m to 15m) spatial sampling, wide swaths (up to 45km) and noise equivalent reflectance (NER) values of less than 0.5%. An evaluation of security risks, vulnerability, and strategies is presented for communications technologies used in gathering, processing, storing, and disseminating global environmental micro and nano sensors and satellite data.
Temperature Dependent Fluorescence of Nanocrystalline Ce-doped Garnets For Use as Thermographic Phosphors
Authors: Hansel Rachael , Allison Steve , Walker Greg
Published: April 2011

Four samples of (Y1−xCex)3(Al1−y Gay)5O12 (where x=0.01, 0.02 and y=0, 0.5) were synthesized via the simple, efficient combustion synthesis method in order to determine the effect of substituting Ga3+ for Al3+ on the temperature-dependent fluorescent lifetime. X-ray diffraction shows that the Ga-doped samples have longer lattice constants and transmission electron microscopy data show that each sample consists of nanocrystallites which have agglomerated in micron-sized particles. Photoluminescence data reveal that the addition of gallium into the YAG:Ce matrix induces a red shift in the absorption spectra and a blue-shift in the emission spectra. The laser-induced fluorescent lifetime was determined as a function of temperature over the range of 0-125°C using two different emission filters. Increasing the amount of dopant ultimately results in a decrease of the fluorescent lifetime. The quenching temperatures for the Ga-doped samples were lower than the samples without gallium. The results of this work show that combustion synthesis is viable method for making highly luminescent, nanocrystalline TGPs. In addition, these results show that the quenching temperature of YAG:Ce can be altered by substituting ions which alter the location of the charge transfer state and by changing the morphology of the sample.
Electrically Pumped Photonic Crystal Distributed Feedback Quantum Cascade Lasers
Authors: Razeghi Manijeh , Bai Yanbo , Slivken Steven , Zhang Wei
Published: April 2011

In parallel with the effort to improve the efficiency of Quantum cascade lasers (QCL) for high power continuous wave (CW) operations, the peak power in pulsed mode operation can be easily scaled up with larger emitting volumes, i.e., processing QCLs into broad area lasers. However, as the emitter width increases, multi-mode operation happens due to poorer lateral mode distinguishability. By putting a two dimensional photonic crystal distributed feedback (PCDFB) layer evanescently coupled to the main optical mode, both longitudinal and lateral beam coherence can be greatly enhanced, which makes single mode operation possible for broad area devices. For PCDFB laser performance, the linewidth enhancement factor (LEF) plays an important role in controlling the optical coherence. Being intersubband devices, QCLs have an intrinsically small LEF, thus serves better candidates over interband lasers for PCDFB applications. We demonstrate electrically pumped, room temperature, single mode operation of photonic crystal distributed feedback quantum cascade lasers emitting at λ ∼ 4.75 μm. Ridge waveguides of 50 μm and 100 μm width were fabricated with both PCDFB and Fabry-Perot feedback mechanisms. The Fabry-Perot device has a broad emitting spectrum and a broad far-field character. The PCDFB devices have primarily a single spectral mode and a diffraction limited far field characteristic with a full angular width at half-maximum of 4.8 degrees and 2.4 degrees for the 50 μm and 100 μm ridge widths, respectively.
Propagation of high-frequency surface plasmons on gold
Authors: Peale Robert Edwin , Lopatiuk-Tirpak Olena , Cleary Justin W , Santos Samantha , Henderson John , Clark David , Chernyak Leonid , Winningham Thomas Andrew , Del Barco Enrique , Heinrich Helge , Buchwald Walter R
Published: April 2011

Surface plasmon propagation on gold over 0.1 – 1.6 micrometer distances for plasmon energies in the range 1.6 – 3.5 eV was characterized. Surface plasmons were excited by an electron beam near a grating milled in the gold. The spectra of out-coupled radiation reveal increasingly strong propagation losses as surface plasmon energy increases above 2.8 eV, but little effect in the range 1.6 – 2.8 eV. These results are in partial agreement with theoretical expectations.
Terahertz Metamaterials on Thin Silicon Nitride Membranes
Authors: Peralta Xomalin G. , Arrington C. L. , Williams J. D. , Strikwerda A. , Averitt R. D. , Padilla W. J. , O'Hara J. F. , Brener I.
Published: April 2011

The terahertz (THz) region of the electromagnetic spectrum holds promise for spectroscopic imaging of illicit and hazardous materials, and chemical fingerprinting using moment of inertia vibrational transitions. Passive and active devices operating at THz frequencies are currently a challenge, and a promising emerging technology for such devices is optical metamaterials. In particular, a chem/bio sensing scheme based on the sensitivity of metamaterials to their dielectric environment has been proposed but may be limited due to the large concentration of electric flux in the substrate. In addition, there is an interest in fabricating 3D metamaterials, which is a challenge at these and shorter wavelengths due to fabrication constraints. In order to address both of these problems, we have developed a process to fabricate THz metamaterials on free-standing, 1 micron thick silicon nitride membranes. We will present THz transmission spectra and the corresponding simulation results for these metamaterials, comparing their performance with previously fabricated metamaterials on various thick substrates. Finally, we will present a scheme for implementing a 3D THz metamaterial based on stacking and possibly liftoff of these silicon nitride membranes.
A Novel Near-field Raman and White Light Imaging System for Nano Photonic and Plasmonic Studies
Authors: Shen Ze Xiang , Kasim J. , You Y. M. , Du C. L.
Published: April 2011

We show the approaches in achieving high resolution Raman and white light imaging. In Raman imaging, a dielectric microsphere is trapped by the incoming laser, which was focused onto the sample by the microsphere. The microsphere was also used to collect the scattered Raman signals. We show the capability of this method in imaging various types of samples, such as Si devices and gold nanopattern. This method is comparatively easier to perform, better repeatability, and stronger signal than the normal near-field Raman techniques. Besides the Raman imaging, we also show a far-field confocal white light reflection imaging system that can be used for the fast imaging and characterization of nanostructures. This system uses a xenon (Xe) lamp as the incident light source and tunable aperture to enhance the spatial resolution. It has a spatial resolution of around 370 nm at a wavelength of 590 nm. With our system, we can clearly resolve images of 300 nm nanoparticles arranged in 2D honeycomb arrays with a period of 500 nm. Localized surface plasmons (LSPs) of isolated single and dimer gold nanospheres were also studied and the resonance energy difference between their LSPs was extracted.
Materials and Components for Flexible and Stretchable Transducers
Authors: Bauer Siegfried
Published: April 2011

Flexible and stretchable electronic components are currently at the heart of macroelectronics research. Materials useful for such applications are based on entropy elastic soft matter, combined with energy elastic functional elements. Examples include functional materials for sensing pressure and temperature changes, such as ferroelectrets, ferroelectric polymers, and nanocomposites of ferroelectric polymers and piezoelectric ceramics. Components for making flexible or stretchable electronic components additionally require electronic circuitry based on amorphous silicon or on organic semiconductors. Progress in such electronic elements is rapid, state of the art are elements which can easily operate at low voltage levels of 1 V. Combined with functional materials, sensing elements for temperature and pressure changes are easily achieved, as demonstrated with a few working examples of paper thin microphones, optothermal switching elements and skin-like electronics. Entropy-elastic elastomers form the basis for actuating elements, outlined by examples based on self organized actuating structures. Such materials can be also made functional by design, enabling fully reversible stretchable sensing elements for temperature, pressure and other physical parameters.
Mechanical Integrity Study of Air Gap Structures Assisted by FE Simulations
Authors: Moreau Stephane , Gaillard Fré;déric , Barbé Jean-Charles , Gras Raphaël , Passemard Gérard , Torres Joaquin
Published: April 2011

In this paper, mechanical reliability of “air gap” structures has been evaluated when a copper line is completely surrounded with air. Different Finite Element (FE) simulation models have been used on a 2-metal level structure to study the M2 copper line bow evolution as a function of its dimensions if complete air cavities are generated underneath (i.e. at via level). Design rules information may therefore be obtained to optimize “air gap” integration considering the 65 nm and 22 nm technology nodes. Thus, we not only highlight that M2 copper line can not collapse considering our failure criterion but that M2 bow variation may also be improved when a tensile SiCN capping layer is deposited on top of the structure. The influence of the interline spacing vs. M2 bow has also been studied and we show that its increase is a beneficial parameter for the air gap structure. In opposite, we demonstrate that buckling can occur when a compressive SiCN layer is used. Finally, we accurately predict the M2 bow variation for air gap structures of the 65 nm and 22 nm technology nodes, but stress and strain distribution can complementary be provided. Those results highlight interesting criteria for designers to build reliable air gap structures.
Moisture Adsorption in Plasma-Damaged Porous Low-k Dielectrics
Authors: Vinogradova Ekaterina , Smith Casey E , Mueller DW , McKerrow Andrew J , Reidy Rick
Published: April 2011

Plasma etch/ash processes can induce changes in low-k film surface/bulk chemistries and topographies resulting in increased water absorption, surface roughness, and metal intrusion. After ashing, the altered surface character of the low-k can impact wetting, adhesion, and, consequently, the resistance of subsequently deposited barrier layers. In this work, we describe the use of deuterium oxide as means of measuring moisture penetration into low-k films. Film chemistries have been monitored using grazing angle attenuated total reflectance (GATR) and transmission Fourier transform infrared spectroscopy (FTIR). To study moisture absorption in porous spin-on and CVD low-k films, unashed and ashed films have been exposed to D2O liquid and vapor treatments under “dry” nitrogen. The extent of D2O uptake, removal and exchange reactions has been studied using transmission and GATR FTIR methods because the D2O and O-D adsorption peaks are distinct from water and O-H as well as other low-k adsorptions. This method can be used to study Si-OH species because deuterium can exchange with hydrogen within silanols under ambient conditions while methyl groups are much less likely to exchange. Three different low-k films, a porous spin-on MSQ (k=2.2), a porous CVD (k=2.3), and an organosilicate glass (OSG, k=2.85) have been used. In FTIR spectra, unashed low-k films show minimal D2O adsorption. In MSQ hydrogen-ashed films, the data suggest the presence of deuterium oxide and O-D peaks. Further, D2O adsorption appears to be considerably higher for ashed films as would be expected due to the hydrophobicity of these films. In the CVD films, there does not appear to be as marked a difference. This method permits the introduction of a chemical “marker” into low-k wet and ambient processes allowing one to distinguish among adsorptions from different aqueous sources.
Off-Angular Deposition Compensation for PVD Selective Re-sputtering Process
Authors: Yang Hsien-Lung , Zhang Fuhong , Nelson Kim , Tseng Jennifer M. , Forster John , Sunddarrajan Arvind , Bhatnagar Ajay , Kumar Niranjan , Gopalraja Prabu
Published: April 2011

In Copper back-end-of-line (BEOL), the “punchthru™ process” – removal of barrier material from via bottom during etch/re-sputter step, and gouging into the underlying Copper line - has been increasingly used in 65nm production for its superior reliability. However, with the adoption of porous low-k dielectric at 45nm node and beyond, the conventional punchthru process can cause physical damage to the porous dielectric, such as roughening of the trench bottom in dual damascene structures, micro-trenching in the bottom of single trenches, which may have reliability implications. This paper reported on the use of off-angular Tantalum neutral flux during the re-sputter process to improve the selectivity between the via and trench bottom in order to protect the trench bottom and via bevel, while still allowing sufficient gouging into the underlying Copper line. In addition, the plasma density and ion energy are adjusted to further optimize selectivity, and to eliminate any micro-trenching. Therefore, this paper demonstrated PVD high deposit/etch selectivity process based on transmission-electron microscopy (TEM) and studies of electrical test result. This approach has extended the PVD Tantalum barrier process to at least 32nm node.
Nanoindentation of Lead Free Solders for Harsh Environments
Authors: Marques Vitor Farinha , Grant Patrick , Johnston Colin
Published: April 2011

To better understand the factors governing the reliability of lead free solders during severe excursions in temperature, the hardness and elastic modulus of the micro-phases formed in a Sn-Ag-Cu/Cu solder joint were characterized using nanoindentation at temperatures from 25 to 175°C. The creep behaviour of the different micro-phases was also studied as function of temperature. The hardness and elastic modulus of Cu6Sn5, Cu3Sn had a weak dependence on temperature, while primary Sn, eutectic regions and electroplated Cu hardness and modulus were sensitive to temperature. Creep studies indicated that intermetallic were more creep resistant than softer phases that readily underwent creep, the type and rate of which was shown to be strongly temperature dependent.