bluuebunny/crossref_metadata_2025 huggingface dataset:
Non Destructive Electrical Defect Characterisation and Topography of Silicon Wafers and Epitaxial Layers
Authors: Dornich K. , Hahn T. , Niklas J.R.
Published: June 2019

Recent progress in experimental technique made it possible to improve the sensitivity of microwave detected photoconductivity by several orders of magnitude. This opens completely new possibilities for a contact less non-destructive electrical defect characterization of silicon wafers and even of epitaxial layers on substrates with extremely low resistivity. Electrical properties such as lifetime, mobility and diffusion length can be measured without contacts also at very low injection levels with a resolution only limited by the diffusion length of the charge carriers. The doping level of the material plays no major role.

Owing to the high sensitivity, thermal excitation of charge carriers out of defect levels filled during the photo pulse can also be observed. This leads to defect specific photoconductivity transients which deliver pieces of information like DLTS, however, again without contacts, non critical doping, and with high spatial resolution.
Morphology, Defects and Thermal Stability of SiGe grown on SOI
Authors: Xie Qianghua , Kottke Mike , Wang Xiangdong , Canonico Mike , White Ted , Nguyen Bich-Yen , Barr Alex , Thomas Shawn , Liu Ran
Published: June 2019

SiGe/SOI films have been investigated by transmission electron microscopy (TEM), atomic force microscopy (AFM) and Raman spectroscopy. For low Ge composition (∼ 20%), strain relaxation in the SiGe layer is minimal (<0.25%). For higher Ge content (32%), the tensile strain in a Si capping layer grown on top of SiGe/SOI is 0.46% (a stress of 0.81 GPa). TEM has revealed that most of the resulting defects at the SiGe/SOI interface and move downward. The misfit dislocation (MD) linear density is 17/μm, being consistent with the strain relaxation of the SiGe layer as determined by Raman spectroscopy. Upon thermal annealing, residual strain in the SiGe films has been further relaxed via two major routes (a) introduction of more MDs, and (b) development of surface undulation. High strain relaxation has been achieved in a SiGe layer grown on a higher-Ge content buffer layer.
Characterization of Ultrathin Strained-Si Channel Layers of n-MOSFETs Using Transmission Electron Microscopy
Authors: Anjum Dalaver H. , Li Jian , Xia Guangrui , Hoyt Judy L. , Hull Robert
Published: June 2019

Strained-Si based Field Effect Transistors (FETs) have enabled improvement of carrier transport in Metal Oxide Semiconductor (MOS)-based devices, both in the ON state of the device and in the sub-threshold region. This leads to devices with higher ratios of on-to-off current, improvements in the device sub-threshold slope, lower voltage operation, and carrier mobility enhancement. However, in order to understand the fundamental physics of these devices, it is important to address the stress conditions of the strained-Si channel layers after device processing, particularly after the ion-implantation process. In this work, we have studied Si+ self ion-implantation and thermally annealed strained-Si channel layers in n-MOSFETs. It has been observed that the density of defects in the strained-Si layer depends upon implant dose as well as thermal treatment. Using energy dispersive spectroscopy (EDS) spectra, it is found that Ge is present in the strained Si layer when analyzed after Si+ implantation and rapid thermal annealing. The presence of Ge in the strained Si channel layer causes relaxation of strain. This is verified by Convergent Beam Electron Diffraction (CBED) by measuring the lattice constant of the strained channel. It is concluded that electron mobility enhancements can be degraded in n- MOSFETs due to presence of both Ge up-diffusion and defects.
Transmission Electron Microscopy Study of Nonpolar a-Plane GaN Grown by Pendeo-Epitaxy on (11

2

0) 4H-SiC.
Authors: Zakharov D.N. , Liliental-Weber Z. , Wagner B. , Reitmeier Z.J. , Preble E.A. , Davis R.F.
Published: June 2019

Pendeo-epitaxy has been applied to nonpolar a-plane GaN layers in order to observe if such process will lead to defect reduction in comparison with direct growth on this plane. Uncoalesced and coalesced a-plane GaN layers with thicknesses 2μm and 12μm, respectively, have been studied by conventional and high resolution electron microscopy. The following structural defects have been observed in pendeo-epitaxial layers: (1) basal stacking faults, (2) threading dislocations, and (3) prismatic stacking faults. A drastic decrease in the density of threading dislocations and stacking faults was observed in ‘wing’ areas with respect to ‘seed’ areas. Cross-section images reveal cracks and voids at the areas where two coalesced wings meet each other. High resolution electron microscopy shows that the majority of stacking faults are low-energy planar defects of the types I1, I2 and I3. The I3 type basal stacking fault, predicted theoretically, was observed experimentally for the first time.
Compositional Changes in the Infrared Optical Properties of Cr Doped CdZnTe Crystals
Authors: Hömmerich U. , Bluiett A.G. , Nyein EiEi , Trivedi S.B. , Shah R.T.
Published: June 2019

We are currently investigating the infrared (IR) optical properties of Cr doped ternary cadmium chalcogenides for potential applications in solid-state lasers and passive optical Qswitches. In this paper, we present compositional changes in the IR optical properties of Cr doped Cd1-xZnxTe single crystals with x=0.05, 0.1, and 0.2. Undoped CdZnTe crystals were grown by vertical Bridgman technique. Cr doping of CdZnTe was achieved through either in-situ doping or through a thermal diffusion process. For comparison, Cr: CdTe and Cr: ZnTe crystals were also prepared. The optical properties of Cr2+ ions were strongly dependent on the host composition and spectral blue shifts were observed with increasing Zn content in Cr: CdZnTe. The IR absorption peak of Cr2+ ions shifted from ∼1910 nm for Cr: CdTe to ∼1815 nm for Cr: Cd0.8Zn0.2Te. Less pronounced blue shifts were observed for the IR emission from Cr: CdZnTe crystals. The spectral shifts can be explained by the decrease in bond-length when going from CdTe to CdZnTe leading to an increased crystal-field effect experienced by Cr2+ ions. A slight broadening of the absorption and emission was also observed in ternary Cr: CdZnTe compounds compared to Cr: CdTe, which suggests that Cr2+ ions were incorporated in multiple lattice sites in CdZnTe. Moreover, the Cr2+ emission dynamics revealed a slightly non-exponential decay behavior for Cr: CdZnTe crystals, whereas the decay time of Cr: CdTe was single-exponential.
Si3H8 Based Epitaxy of Biaxially Stressed Silicon Films Doped with Carbon and Arsenic for Cmos Applications
Authors: Bauer M. , Zollner S. , Theodore N. D. , Canonico M. , Tomasini P. , Nguyen B.-Y. , Arena C.
Published: June 2019

Arsenic doped Si:C films were grown epitaxially using Silcore® (Si3H8), methylsilane and arsine as source gases with growth rates up to 90 nm/min at 550°C. We observed a strong dependence of C and As incorporation on growth rate, caused by a growth rate dependent surface segregation behavior of C and As. High-resolution x-ray diffraction measurements of the epi layers reveal a perpendicular lattice constant as low as 5.323 Å. This corresponds to a biaxial stress of more than 2 GPa. Grazing exit (224) x-ray diffraction reciprocal space maps show the full tetragonal strain expected from the C content, suggesting that no relaxation of the films has occurred. Spectroscopic ellipsometry (SE) spectra were acquired in the 0.74 to 6.6 eV photon energy range. For intrinsic Si:C alloys, the E1 critical point shows the expected blueshift due to the alloying. For Si:C:As, a strong broadening of the E1 and E2 transitions exists, due to scattering of Bloch electrons in the crystal by As atoms. Additionally, free carrier effects lead to a decrease (increase) of the real (imaginary) part of the dielectric function in the near-infrared, consistent with a free carrier concentration in excess of 5×1020 cm-3. Transmission electron microscopy (TEM) of As doped Si:C films confirmed single-crystal epitaxial growth.
Transmission Electron Microscopy Studies of Strained Si CMOS
Authors: Xie Qianghua , Fejes Peter , Kottke Mike , Wang Xiangdong , Canonico Mike , Theodore David , White Ted , Sadaka Mariam , Vartanian Victor , Thean Aaron , Nguyen Bich-Yen , Barr Alex , Thomas Shawn , Liu Ran
Published: June 2019

In this paper, various types of defects (both threading dislocation and misfit dislocations) in strained Si (sSi) have been analyzed by transmission electron microscopy (TEM). Germanium upper-diffusion has been studied by scanning transmission electron microscopy (STEM) for strained Si on SiGe/SOI. SGOI-devices processed using an optimized thermal budget show minimal Ge diffusion and minimal process related defects. Correlation between the device performance (such as leakage current and reliability) and structural information found in TEM has been established.
Radiative Versus Nonradiative Decay Processes in Germanium Nanocrystals Probed by Time-resolved Photoluminescence Spectroscopy
Authors: Giri P. K. , Kesavamoorthy R. , Panigrahi B. K. , Nair K.G.M.
Published: June 2019

Ge nanocrystals (NCs) of diameter 4–13 nm are grown embedded in a thermally grown SiO2 layer by Ge ion implantation and subsequent annealing. Steady state and time-resolved photoluminescence (PL) studies are performed on these embedded Ge nanocrystals to understand the origin of the PL emission at room temperature. Steady state PL spectra show a broad peak consisting of a peak at ∼2.1 eV originating from Ge NCs and another peak at ∼2.3 eV arising from ion-beam induced defects in the Ge/SiO2 interface. Time-resolved PL studies reveal double exponential decay dynamics of the PL emission on the nanoseconds time scale. The faster component of the decay with large amplitude and having a time constant τ1∼3.1 ns is attributed to the nonradiative lifetime, since the time constant reduces with increasing defect density. The slower component with time constant τ2∼10 ns is attributed to radiative recombination at the Ge NCs. These results are in close agreement with the theoretically predicted radiative lifetime for small Ge NCs.
Elastic Stress Relaxation at Nanoscale: A Comprehensive Theoretical and Experimental Investigation of the Dislocation Loops Associated with As-Sb Nanoclusters in GaAs
Authors: Chaldyshev V.V. , Kolesnikova A.L. , Bert N.A. , Romanov A.E.
Published: June 2019

A comprehensive experimental and theoretical investigation was performed for the system of As-Sb nanoclusters and nanoscale dislocation loops in GaAs:Sb films grown by molecular beam epitaxy at low temperature and subsequently annealed. A model was developed for the elastic stress relaxation, self-energies and interactions in such cluster-loop nanosystems. The model was based on the experimental investigation of the microstructure of the As-Sb nanoclusters by transmission electron microscopy. The atomic structures of the As-Sb nanoclusters and dislocation loops, as well as their orientation relationships were determined. A strong anisotropic mismatch between the As-Sb nanoclusters and GaAs matrix has been revealed. This mismatch was proven to be a reason for the formation of the prismatic nanoscale dislocation loops nearby the nanoclusters. Our theoretical model explores the elastic properties of an inclusion with uniaxial dilatation. For such inclusions, the elastic stresses and stored energy are determined in a closed analytical form. The theoretical analysis predicts a specific non-linear dependence of the dislocation loop diameter on the cluster diameter, which fits well the experimentally observed one. It is demonstrated that both the change in the inclusion self energy due to diminishing dilatation and the interaction between the dislocation loop and inclusion are important in the relaxation phenomena at stressed nanoscale inclusions in semiconductors.
Infrared Spectroscopy of Impurities in ZnO Nanoparticles
Authors: Hlaing Oo W. M. , McCluskey M. D.
Published: June 2019

Semiconductor nanoparticles have a range of potential applications in electronic, optoelectronic and spintronic devices. Zinc oxide (ZnO), a wide-bandgap semiconductor, has emerged as an important material for such applications. In this work, impurities in ZnO nanoparticles were investigated with infrared (IR) spectroscopy, and the results show the presence of CO2 impurities in ZnO nanoparticles. Isotopic substitution was used to verify the frequency assignment and the results demonstrate conclusively that the impurities originate from the precursors. Isochronal annealing experiments were performed to study the formation and stability of the CO2 molecules. In addition to unintentional CO2 impurities, we intentionally introduced hydrogen into ZnO nanoparticles. Our results show that post-growth annealing in hydrogen dramatically changes IR transmission, reflection and electrical properties of the nanoparticles.
Conductivity Enhancement in Thin Silicon-on-Insulator Layer Embedding Artificial Dislocation Network
Authors: Ishikawa Yasuhiko , Yamauchi Kazuaki , Yamamoto Chihiro , Tabe Michiharu
Published: June 2019

A nanometer-scale dislocation network is artificially formed in thin top Si layer of silicon-on-insulator (SOI) structure, and effect of the dislocation network on the transport property is examined from the viewpoint of nanodevice applications. The artificial network of screw dislocations was formed in the Si layer using a wafer bonding of a pair of (001) SOI wafers with a slight misalignment of the in-plane crystalline directions to cause a lattice mismatch. The transmission electron microscopy clearly revealed the formation of dislocation network at the bonding interface with the period less than ∼20 nm. The dislocation network was found to enhance the conductivity in the Si bicrystal layer more than one order of magnitude in comparison with that in the monocrystal layer free from the dislocations. The enhanced conductivity is probably derived from an increased concentration of electrons around the dislocations due to the formation of donor-like gap states.
Silicon Single-Electron Pump and Turnstile: Interplay with Crystalline Imperfections
Authors: Ono Yukinori , Fujiwara Akira , Takahashi Yasuo , Inokawa Hiroshi
Published: June 2019

The single-electron device (SED), which has quantum dot(s), or island(s) in its core, enables the control of electron motion on the level of an elementary charge. The single-electron pump and turnstile are members of the SED family and enable single-electron transfer synchronized with the gate clock. They have the potential for extremely low error rates of electron transfer and are thus expected to be building-block devices for future information processing and electrical metrology. We have been pursuing the fabrication of Si-based SEDs using CMOS technology with the help of electron-beam lithography and have recently demonstrated a Si single-electron pump and turnstile. They are composed of one Si quantum dot and two tiny MOS gates and have dramatically increased the operation temperatures, which opens up the possibility of the practical use of the pump and turnstile.

Another path to realizing single-electron transfer, which we will discuss here, might be to use a localized state in the Si bandgap instead of quantum dots. The localized states could in principle be donor/acceptor levels or any other states created by crystalline imperfections. They are free from the problem of the critical size control of the quantum dots, which might lead to a new era of single-electronics in combination with the rapidly developing research field of “dopant engineering”.
Bubbles and Cavities Induced by Rare Gas Implantation in Silicon Oxide
Authors: Ntsoenzok E. , Assaf H. , Ruault M.O.
Published: June 2019

In this pioneering study, we have extended noble-gas implant-induced cavity generation in Si and other semiconductors to a dielectric, viz., SiO2 by implanting a variety of inert gas species. It has been seen that helium and neon do not induce bubbles/cavities in SiO2, regardless of implantation parameters and nature of the sample. Krypton and xenon implantation however result in bubbles/cavities formation in the oxide layer. In the case of Xe a minimum threshold dose of about 1016 cm-2 is needed for their formation. Characterization by cross-section transmission electron microscopy (XTEM) and Rutherford backscattering spectrometry (RBS) showed that bubbles/cavities remain even after a 1100°C anneal, while Xe strongly desorbs out at that temperature. C-V measurements reveal that the effective dielectric constant K is reduced from 3.9 SiO2 for bulk SiO2 to < 2.6, thus making this technique very attractive for low-k applications in Si technology.
A New Post Annealing Method for AlGaN/GaN Heterostructure Field-Effect Transistors Employing XeCl Excimer Laser Pulses
Authors: Ha Min-Woo , Lee Seung-Chul , Park Joong-Hyun , Seo Kwang-Seok , Han Min-Koo
Published: June 2019

A new post annealing method employing excimer laser pulses is proposed to improve the transfer characteristics and the breakdown voltage of the unpassivated AlGaN/GaN heterostructure field-effect transistor (HFET) and the passivated one. The XeCl excimer laser pulses with wavelength of 308 nm anneal the AlGaN/GaN HFET after the Schottky gate metallization. The interface defects between the Schottky gate metal and a GaN layer is decreased by the lateral heat diffusion of the laser pulses. Our experimental results show that the drain current and the maximum transconductance of the unpassivated AlGaN/GaN HFET after laser pulses annealing are 496 mA/mm and 134 mS/mm while a virgin device shows 434 mA/mm and 113 mS/mm, respectively. The proposed method anneals effectively the SiO2 passivated AlGaN/GaN HFET and the leakage current of the passivated device is decreased from 483 nA to 29 nA.
Hydrogen Diffusion in Boron-Doped Hydrogenated Amorphous Silicon Films: Crystallization and Induced Structural Changes
Authors: Kail F. , Hadjadj A. , Cabarrocas P. Roca i
Published: June 2019

We have studied the evolution of the structure of boron-doped hydrogenated amorphous silicon films exposed to a hydrogen plasma. From the early stages of exposure, hydrogen diffuses and forms a thick H-rich subsurface. At longer times, hydrogen plasma leads to the formation of a microcrystalline layer via chemical transport without crystallization of the initial layer. We observe that the hydrogen content increases in the films during a plasma exposure and once the microcrystalline layer is formed hydrogen diffuses out of the sample accompanied with a decrease in the boron content. This effect can be attributed to the electric field developed within the heterojunction a-Si:H/μc-Si:H that drives the positively charged hydrogen atoms in the boron-doped layer towards the μc-Si:H layer.
Fabrication of Silicon Carbide PIN Diodes by Laser Doping and Planar Edge Termination by Laser Metallization
Authors: Tian Z. , Quick N.R. , Kar A.
Published: June 2019

Silicon carbide PIN diodes have been fabricated using a direct write laser doping and metallization technique. Trimethyaluminum (TMA) and nitrogen are precursors used to laser dope p-type and n-type regions, respectively, and μ4.3 mm p-type doped junction and 4 mm ntype doped junction are fabricated in semi-insulating 6H-SiC wafers. Rutherford backscattering studies show that no amorphization occurred during the laser doping process. A planar edge termination is fabricated by laser metallization in argon ambient to form a high resistivity layer. With this termination, the leakage current of the PIN diodes can be suppressed effectively compared to that of diodes without edge termination. The performance of the diodes can also be tailored by shrinking the active area of the diode and by conventional annealing.
Photoelectron Emission Technique for the Surface Analysis of Silicon Wafer Covered with Oxide Film
Authors: Sakurai Takao , Momose Yoshihiro , Kudou Masanori , Nakayama Keiji
Published: June 2019

A new analysis method using the photoelectron emission yield spectra near threshold has been developed to characterize solid surfaces exposed to ambient air. The application of the analysis method to the yield spectra for a Si (100) wafer surface covered with a native oxide film revealed that three emission peaks are cumulated on the basic yield spectrum line for the silicon. It was indicated that these peaks have a Gaussian-shaped density distribution and the energy levels are located at 5.37, 5.68, and 6.02 eV below the vacuum level, respectively.
Identification and Characterization of Submicron Defects for Semiconductor Processing
Authors: Liu Wei , Fausz Aime , Svoboda John , Butcher Brian , Williams Rick , Schauer Steve
Published: June 2019

Auger Electron Spectroscopy (AES) is one of the few techniques that has surface sensitivity and small analysis volume to make it the ideal analytical technique for the compositional characterization of submicron defects. However, the integration of defect inspections at only a few processing steps during device fabrication results in the detection of many buried defects. In order to identify these defects, it is necessary to determine their composition. Combined with Focused Ion Beam (FIB) technique to expose the cross section of the buried defect, Auger analysis provides accurate identification of buried defects that are critical for quickly ramping to higher yields and recovering from yield excursions. This paper reports two examples of the use of AES combined with FIB to diagnose processing problems.
Optical and Electrical Characterization of Quantum Dot Infrared Photodetector Structure Treated with Hydrogen-Plasma
Authors: Nam H.D. , Song J.D. , Choi W.J. , Lee J.I. , Yang H.S.
Published: June 2019

We have carried out hydrogen-plasma (H-plasma) treatments on a quantum dot infrared photodetector (QDIP) structure, with a 5-stacked InAs dots in an InGaAs well structure and a Al0.3Ga0.7As/GaAs superlattice barrier. The sample structures were grown by molecular beam epitaxy. The H-plasma treatment has been carried out at 150 °C for 3 min – 40 min with 40 sccm of H2 gas flow rate and 10 W of RF power. After H-plasma treatment, photoluminescence (PL) intensities of the samples were slightly reduced compared to that of as-grown sample, without any changes in their PL peak position. The dark currents of H-plasma treated samples were much smaller by many orders of magnitudes than that for as-grown sample. The sample exposed to Hplasma for 10 min showed the lowest dark current, enabling the observation of photocurrent with a wide spectrum between 3 – 12 μim at 11 K.
Blistering and Splitting in Hydrogen-implanted Silicon
Authors: Ntsoenzok E. , Assaf H. , Ashok S.
Published: June 2019

We implanted hydrogen in silicon with energies ranging from 500 keV to 2 MeV for implant depths varying from 6.1 to 48.4 μm according to TRIM (transport of ions in matter) 2003. After implantation, a 600 °C thermal annealing was applied to all samples. It is found that for depths lower than 9 μm there is no lift-off of a free-standing silicon layer; only a blistering phenomenon is seen. Increase in the implanted dose or thermal budget does not improve the situation. However, for depths ≥9 μm (9 - 50 μm in this study) thermal annealing results in effective detachment of ultra-thin free-standing layers. This technique hence provides high quality thin Si layers for semiconductor technology.
Erbium Doped Silicon Single- and Multilayer Structures for LED and Laser Applications
Authors: Krasilnik Zakhary F. , Andreev Boris A. , Gregorkiewicz Tom , Jantsch Wolfgang , Klik Mark A.J. , Kryzhkov Denis I. , Krasilnikova Ludmila V. , Kuznetsov Viktor P. , Przybylinska Hanka , Remizov Dmitry Yu. , Shengurov Vladimir G. , Shmagin Viacheslav B. , Stepikhova Margarita V. , Timoshenko Victor Yu. , Vinh Nguyen Q. , Yablonskiy Artem N. , Zhigunov Denis M.
Published: June 2019

The paper is a brief retrospective review of our contribution to the Si:Er problem in the last decade. It contains a description of the experimental facilities, results of the light emitting media (Si:Er and Si1-xGex:Er) research and device applications.
GaN:Eu Interrupted Growth Epitaxy (IGE): Thin Film Growth and Electroluminescent Devices
Authors: Munasinghe Chanaka , Steckl Andrew , Nyein Ei Ei , Hömmerich Uwe , Peng Hongying , Everitt Henry , Fleischman Zack , Dierolf Volkmar , Zavada John
Published: June 2019

The GaN:RE phosphor development plays a major role in the GaN:RE AC thick dielectric electroluminescent (TDEL) device optimization. In this paper we report on EL devices fabricated using Eu-doped GaN red phosphors films grown by interrupted growth epitaxy (IGE). IGE consists of a sequence of ON/OFF cycles of the Ga and Eu beams, while the N2 plasma is kept constant during the entire growth time. IGE growth of GaN:Eu resulted in significant enhancement in the Eu emission intensity based primarily at 620.5nm. The increase in the material crystallinity observed with the IGE phosphors appears to be the dominant cause of the emission enhancement. Thick dielectric EL devices fabricated on glass substrates using IGE-grown GaN:Eu have resulted in luminance of ∼1000 cd/m2.
Study of Optical Gain in Thick GaN Epilayers by Variable Stripe Length Technique
Authors: Tamulaitis G. , Mickevic J. , Shur M. , Fareed Q. , Gaska R.
Published: June 2019

We report on the gain study in high-quality thick GaN layers using the Variable Stripe Length (VSL) technique. The layers were grown by Migration Enhanced Metal Organic Chemical Vapor Deposition (MEMOCVDTM). The amplification of light was investigated for the propagation directions along the layer surface (perpendicular to the c-axis of the crystal) and perpendicular to the layer (along the c-axis) for the layers with thicknesses up to 11 νm. By fitting the experimental stripe length dependence of the edge luminescence with one-dimensional description of light amplification in medium with positive gain, peak gain coefficients of up to 7300 cm-1 were estimated in GaN at the excitation power density of 2 MW/cm2. We discuss limitations of the VSL technique due to the assumption of one-dimensional light propagation and strong influence of gain saturation in a high-gain medium. The contribution of new gain modes after saturation of the highest-gain modes was observed. The optical gains in GaN samples with different carrier lifetimes (obtained using time-resolved photoluminescence and light-induced transient grating techniques) were compared.
Synthesis and Unprecedented Electro-Optic Response Properties of Twisted π-System Chromophores
Authors: Kang Hu , Facchetti Antonio , Jiang Hua , Zhu Peiwang , Marks Tobin J.
Published: June 2019

A series of unconventional twisted intramolecular charge-transfer (TICT) chromophores was designed and synthesized. These chromophores exhibit ultra-large first hyperpolarizabilities. The structural characteristic that promotes this unusual nonlinear optical response is a sterochemically enforced reduction of the D- π-A conjugation that enforces zwitterionic behavior in the ground state and provides a low-energy, large-oscillator strength intramolecular excitation feature. The consequence is that molecules with relatively small numbers of π-electrons exhibit responses far larger than those of traditional planar π-conjugated chromophores. At 1907 nm, non-resonant νβ values as high as -466,000 × 10-48 esu are observed.
Highly Fluorinated Hybrid Glasses doped with (Erbium-ions/CdSe Nanoparticles) Designed for Advanced Laser Amplifiers
Authors: Choi Kyung M. , Rogers John A.
Published: June 2019

Bridged polysilsesquioxanes were synthesized by modifying the Si-O-Si polymeric network to produce highly nanoporous glasses for facile and uniform doping of nanoparticles. By taking advantages of void volumes created through the molecular modification technique, we designed and synthesized hexylene- and fluoroalkylenebridged polysilsesquioxanes doped with both Er+3 ions/CdSe nanoparticles for amplifier applications. Significant enhancement in fluorescence intensity at 1540 nm has been observed from the fluoroalkylene-bridged glass. Analysis by nuclear magnetic resonance (NMR) indicates a dramatically enhanced degree of condensation and a low level of hydroxyl environment in the fluoroalkylene-bridged hosts. The presence of CdSe nanoparticles, by virtue of their low phonon energy, also appears to significantly influence the nature of the surrounding photoluminescence environment of Er+3 ions in those organically modified hosts, resulting in the increased photoluminescence intensity.
Fabrication of Er3+/Pr3+ Co-doped Soda-lime Glass Thin Films Using RF Magnetron Sputtering Method and Optical Property Characterization
Authors: Shin Sang-Hoon , Kim Sung-Dae , Moon Jong-Ha , Kim Jin Hyeok
Published: June 2019

Er3+/Pr3+ co-doped soda-lime glass thin films have been fabricated using RF magnetron sputtering method and their structural and optical properties have been studied. Deposition rate, crystallinity, and composition of glass thin films were investigated by scanning electron microscopy, transmission electron microscopy, and electron probe micro area analysis. Refractive index, birefringence and binding characteristics have been investigated using a prism coupler and x-ray photoelectron spectroscopy. Er3+/Pr3+ co-doped soda lime glass thin films were prepared by changing substrate temperature (room temp.∼550 ), RF power (90W∼150W), and Ar/O2 gas flow ratio at processing pressure of 4mTorr. Glass thin films could be obtained at the optimized processing condition at 350, RF power (130W), and gas flow (Ar:O2=40:0) with maximum deposition rate of 1.6νm/h. Refractive index increased from 1.5614 to 1.5838 and birefringence increased from 0.000154 to 0.000552 as the content of Pr3+ increased. Binding energy of Pr3d increased as the content of Pr3+ increased.
Luminescence of Rare Earth Doped Si/ZrO2 Co-Sputtered Films
Authors: Rozo C. , Fonseca L. F. , Resto O. , Weisz S. Z.
Published: June 2019

Er3+, Nd3+ and Tm3+ doped Si/ZrO2 thin films have been prepared by rf co-sputtering. The films are 5 inches long and divided into 50 sections or positions, labeled from P1 to P50. The target configuration is such that the main target is ZrO2 (181.46 cm2), the rare earth (RE) oxide pellet (1.43 cm2) is placed on the main target below the middle of section of the film and the Si chip (6.67 cm2 or 6.00 cm2) is placed on the main target below one end of the film (P40 to P50). The films were annealed to 700°C. The Er3+4I13/2→4I15/2 emission was detected but no 4I13/2→4I15/2 emission was detected. The 4I13/2→4I15/2 emission shows a narrow peak at 1527 nm (FWHM = 6.5 nm for P20) with two weaker side bands from 1430 nm to 1500 nm and from 1550 nm to 1600 nm. The Nd3+4F3/2→4I9/2, 4F3/2→4I11/2, and 4F3/2→4I13/2 emissions were detected being the 4F3/2→4I11/2 peaked at 1065 nm (FWHM = 39.5 nm for P30) the strongest. The 4F3/2→4I9/2 emission is relatively weak, less than one-fourth the peak intensity of the 4F3/2→4I1/2 emission but is broad (FWHM = 92 nm for P30). No Er3+4I13/2→4I15/2 emission or Nd3+4F3/2 emissions were detected for the Si rich ends of the respective films, being the emission stronger from the Si poor end of the film towards the middle of the film. The maximum Er3+4I13/2→4I15/2 emission is for P20 and the maximum peak intensity for the Nd3+4F3/2→4I11/2 emission is for P30. The excitation wavelength dependence behavior for the Nd3+4F3/2→4I11/2 emission is that typical of energy transfer from the Si nanoparticles to the emitting Nd3+ ions. The excitation wavelength behavior for the Er3+4I13/2→4I13/2 emission reflects a mix of energy transfer from the Si nanoparticles and strong absorption for excitation wavelengths of 488.0 nm and 514.5 nm. The Tm3+ doped Si/ZrO2 thin film does not exhibit infrared (IR) PL from the 3H4 emission or the 3F4→3H6 emission. The intense band from 500 nm to 800 nm observed for all of the RE doped Si/ZrO2 films, due to defects in ZrO2, barely permits the detection of the Tm3+3H4→3H6 emission which is best observed for P35.
Erbium-doped Amorphous- Si-C-O Matrix (a-SiCxOy:Er) - A Novel Silicon-based Material for Near-infrared Optoelectronic Applications
Authors: Gallis Spyros , Huang Mengbing , Nikas Vasileios , Efstathiadis Harry , Eisenbraun Eric , Kaloyeros Alain E. , Nyein Ei Ei , Hommerich Uwe
Published: June 2019

We have synthesized amorphous- SiCxOy (a-SiCxOy) (x, y: 0 - 1.65) materials via thermal chemical vapor deposition (TCVD) at 800°C using a single source oligomer, 2,4,6-trimethyl-2,4,6-trisila-heptane (C7H22Si3) and ultra-high purity oxygen (O2). The Er-doped SiCxOy materials exhibited a strong room-temperature photoluminescence (PL) at ∼1540 nm at an excitation wavelength of 496.5 nm. Furthermore, the infrared PL intensity was found to be highly dependent on the compositions of carbon and oxygen, with the maximum PL intensity obtained for an Er-doped SiC0.50O1.00 thin film, which exhibited a ∼20-times enhancement in the PL intensity as opposed to the Er-doped SiO2 control samples.

The PL intensity decreased significantly as the matrix evolves into either the SiC-like or SiO2-like material. Fourier transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS) were used to characterize the local elemental electronic environment in a-SiCxOy. Our work indicates a strong correlation between the emission of Er luminescence and the formation of Si-C-O bonding in materials.
Nanocrystalline Rare Earth-doped Gallium Nitride Phosphor Powders
Authors: Hirata G.A. , Tao J. , Chen P. , Mishra K.C. , McKittrick J.
Published: June 2019

We report on the fabrication and luminescent properties of rare earth-doped gallium nitride (GaN) phosphor powders. Single phase GaN and GaN:RE3+ powders were prepared by using a novel chemical route.

In this work a new method for the synthesis of high purity, single phase doped GaN powders is reported. (Ga1-xREx)N powders are obtained by dissolving metal nitrates (Ga(NO3)3, (RE(NO3)3) in deionized water and an organic fuel (hydrazine) in order to form a gallium/RE amorphous/nanocrystalline powder. The RE-oxide powders are then reacted with heated ammonia at different temperatures and processing times producing GaN:RE phosphors. X-ray diffraction analysis showed that single phase GaN powders are formed. Preliminary results show (Ga0.95Eu0.05)N powders are luminescent, with the main emission occurring at 611 nm which is due to the 5Do→7F2 transitions in Eu3+. High-purity GaN powders are obtained according to Xray photoelectron spectroscopy (XPS) chemical analysis. Low-temperature cathodoluminescence and photoluminescence measurements indicate that the emission at λ=611 nm is originated from energy transfer from the host to the rare earth ion and to a direct excitation to the Eu3+ electronic levels.

This method can be used to obtain red-luminescence GaN:Eu3+ and other rare earth (e.g. Er, Tb, Tm)-doped GaN powders to produce green and blue luminescence as well.
Potential-pH Diagrams of Interest to Chemical Mechanical Planarization of Copper Thin Films
Authors: Aksu Serdar
Published: June 2019

Chemical mechanical planarization (CMP), which can globally planarize both silicon dioxide (the prevalent interlayer dielectric), and copper films, has become the key process in the damascene method used for producing integrated circuit (IC) devices with multilevel copper interconnects. Cu CMP is typically carried out with slurries containing oxidizing agents, complexing agents, and corrosion inhibitors as the principal chemical components. In such slurries, complexing agents enhance the solubility of copper and increase the dissolution rate of the abraded material in Cu CMP. They also assist achieving high copper removal rates during dynamic polishing conditions. The nature of the complexing agent used, the pH and the redox potential of the slurry system are among the main factors controlling the dissolution and passivation behaviors of copper during CMP. Consequently, these factors are intimately related to the key CMP performance metrics such as removal rate and planarity. In this paper, potentialpH diagrams of copper in aqueous systems containing a number of organic complexing agents including ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), oxalic acid and malonic acid are presented. The predominance regions of copper complexes under different copper and ligand activities and their implications on copper removal during CMP are discussed.
Investigation on Abrasive Free Copper Chemical Mechanical Planarization for Cu/low k and Cu/ultra low k interconnects
Authors: Balakumar S. , Haque T. , Kumar R. , Kumar A.S. , Rahman M.
Published: June 2019

Abrasive Free Copper Chemical Mechanical Polishing (AF-CMP) was developed for Cu/low k materials. Blanket film Cu removal rate of 6000 Å/min with very less non-uniformity of 3% achieved for polishing pressure of 1.5 psi. CMP process window and lower critical pressure were identified with pattern wafers. Material removal mechanism was studied using surface morphology of Copper blanket wafers polished using different pressure, rotation rate and slurry flow rate. Material Removal Mechanism (wear mechanism) such as Chemical wear (etching) and mechanical wear (fatigue wear, particle adhesion wear and abrasion wear) have been found. The increase of slurry flow rate and relative velocity and the decrease of pressure give the dominance of chemical wear in material removal mechanism, and vice versa. Dishing control was achieved during Cu polish using different carrier/platen speed for Cu/SiLKTM patterned wafers. The cumulative distribution of the metal line-to-line leakage current measurements of wafers shows good performance and it is comparable to abrasive process.
Feasibility of Detecting Barrier Layer to Low-k Transition in Copper Cmp Using Raman Spectroscopy
Authors: Kondoju S. , Juncker C. , Lucas P. , Raghavan S. , Fischer P. , Moinpour M. , Oehler A.
Published: June 2019

In copper CMP, transitions from copper to barrier as well as barrier to dielectric layer are typically sensed in situ using an optical reflectance technique. Spectroscopic techniques such as Raman, which allow monitoring the vibrational modes of silicon and low-k layers, have interesting potential for detecting these transitions. In this paper the use of Raman spectroscopy in detecting in situ removal of barrier layers from CDO materials is reported. Intensities of Raman peaks characteristic of Si-Si vibrations from Si substrate and C-H vibrations from low-k materials have been used for monitoring CDO layer thickness and detecting removal of Ta overlayer. An abrasion cell is integrated with a Raman spectrometer to demonstrate the feasibility of Raman monitoring in-situ. Capabilities and limitations of the Raman spectroscopic method are discussed.
Effect of Particle Size Distribution on Filter Lifetime in Three Slurry Pump Systems
Authors: Litchy Mark R. , Schoeb Reto
Published: June 2019

Delivery systems are often used to supply the slurry used to planarize wafers during semiconductor chip manufacturing. These systems pressurize the slurry to deliver it to the tools and circulate it to help keep the particles in suspension. Pressurization and circulation are accomplished by various means including a variety of pumps and pressure-vacuum technology. Typically, slurry passes through a distribution system approximately 100 times before it is used to polish wafers[1].
Optimization of Psiloquest's Application Specific CMP Pads for Commercialization
Authors: Zantye Parshuram B. , Obeng Yaw , Mudhivarthi S. , Kumar Ashok
Published: June 2019

There is a need for metrology, characterization and optimization of CMP pad architecture before being put into service. psiloQuest, Inc. has developed a novel polishing pad which is made up of polyolefin material instead of conventional polyurethane. The surface of the pad has been modified to match the surface of the material under going CMP. In this research, we have optimized the PECVD tetraethylorthosilicate (TEOS) surface coating duration and pad thickness for optimum pad output. The pad was then extensively characterized using the several standard metrology techniques such as SEM, XPS and nanoindentation. The CMP performance evaluation of all the candidate pads was done using CETR CP-4TM bench top CMP tester. There was a correlation and interdependence of the pad coating time and surface chemical, micromechanical and tribological properties. However, their impact on the pad CMP performance was found to be indirect, if any. These findings were used to optimize the pad design and architecture before commercialization. The demonstrated methodology can also be implemented for parametric optimization of polishing pads with novel designs in the future.
Quantitative In-Situ Measurement of Asperity Compression Under the Wafer During Polishing
Authors: Gray Caprice , Apone Daniel , Rogers Chris , Manno Vincent P. , Barns Chris , Moinpour Mansour , Anjur Sriram , Philipossian Ara
Published: June 2019

The interaction of the wafer, slurry and pad determines the material removal rate during Chemical Mechanical Planarization (CMP). Dual emission laser induced fluorescence (DELIF) provides a means to measure the slurry layer thickness between the wafer and a Fruedenbergy FX9 pad during CMP with high spatial (4.3 μm/pixel) and temporal resolution (2 Hz). In this paper we present some preliminary measurements of pad compression using DELIF to measure the standard deviation of asperity height. Static slurry layer images were captured at high (70 kPa) and low (0 kPa) down-force applied to the wafer. In-situ, dynamic images at 10 kPa downforce applied to etched wafers were imaged. Two wafers were etched such that they contain square wells, one wafer with 27 μm and the other will 14.5 μm deep wells. In the static case, asperity compression is directly related the amount of fluid displaced. In the dynamic case, asperity compression is 35% greater under the 27 μm wells than the 14.5 μm wells.
Synergy between Chemical Dissolution and Mechanical Abrasion during Chemical Mechanical Polishing of Copper
Authors: Che Wei , Bastawros Ashraf , Chandra Abhijit
Published: June 2019

The synergistic roles of chemical dissolution and mechanical abrasion on the material removal mechanism during CMP process are explored. A set of nano-wear experiments are conducted on electro-plated copper surfaces with systematic exposure to active slurries. Initial results of in situ wear test in chemically active slurry showed an increased material removal rate (MRR) relative to a dry wear test. To understand the synergistic effects of chemical dissolution and mechanical abrasion, we have investigated two plausible mechanisms of material removal. Mechanism-I is based on chemical dissolution enhanced mechanical abrasion. A soft layer of chemical products is assumed to be formed on top of the polished surface due to chemical reaction with a rate much faster than the mechanical abrasion rate. It is then followed by a gentle mechanical abrasion of that soft layer. An increase in the MRR of up to 100% is identified based on the etching time and the down force. Mechanism-II is based on mechanical abrasion accelerated chemical etching. In this case, the nano-wear experiments are first performed to generate local variation of the residual stress levels, and then followed by chemical etching to investigate the variation of the wear depth and the evolution of surface topography due to etching. It is found that the residual stress caused by the mechanical wear enhances the chemical etching rate, as manifested by the increase of wear depth. The developed understanding from these experiments can be used in future studies to control the rates of chemical dissolution and mechanical abrasion as well as investigating the various process-induced defects.
Modeling of Polishing Regimes in Chemical Mechanical Polishing
Authors: Yeruva Suresh B. , Park Chang-Won , Moudgil Brij M.
Published: June 2019

Chemical mechanical polishing (CMP) is widely used for local and global planarization of microelectronic devices. It has been demonstrated experimentally in the literature that the polishing performance is a result of the synergistic effect of both the chemicals and the particles involved in CMP. However, the fundamental mechanisms of material removal and the interactions of the chemical and mechanical effects are not well understood. A comprehensive model for CMP was developed taking into account both the chemical and mechanical effects for monodisperse slurries. The chemical aspect is attributed to the chemical modification of the surface layer due to slurry chemistry, whereas the mechanical aspect is introduced by indentation of particles into the modified layer and the substrate depending on the operating conditions. In this study, the model is extended to include the particle size and pad asperity distribution effects. The refined model not only predicts the overall removal rate but also the surface roughness of the polished wafer, which is an important factor in CMP. The predictions of the model show reasonable agreement with the experimental observations.
Investigating the Effects of Diluting Solutions and Trace Metal Contamination on Aggregation Characteristics of Silica-Based ILD CMP Slurries
Authors: DeNardis D. , Choi H. , Kim A. , Moinpour M. , Oehler A.
Published: June 2019

One of the major drawbacks to CMP is the tendency for abrasive particles in slurries to form aggregates, which have the potential to cause defects on wafer surfaces. Therefore, it is crucial to understand the mechanisms by which aggregates are formed so appropriate metrology can be implemented that will identify defect-causing slurries before they are used in the fab. Single particle optical sensing (SPOS) techniques are commonly used to obtain large particle counts (LPC) for slurries. The SPOS technique requires slurry dilution before measuring and the instrument continues to dilute the sample during a measurement. Other techniques that can be used to characterize slurries are particle size distribution by static light scattering (SLS), mean particle size (MPS) by dynamic light scattering (DLS), and zeta potential (ZP) measurements. Like SPOS, all of these techniques require that slurry be diluted prior to measuring and the current method for doing so is with UPW. Diluted slurry demonstrates significantly different ionic strength than the undiluted slurry, and electrolyte concentration has been shown to affect aggregation and electric double layer characteristics of silica particles 2–6. An alternative diluting solution was formulated that simulates the conductivity and pH of the original slurry to mimic the conditions to which particles are actually exposed. It is crucial to identify the metrology that is compatible with high pH solutions and the impact of these solutions on measurements. A second objective of the study is to examine aluminum contamination in slurries. To date, the aluminum content of silica-based CMP slurries and effects on performance have not been well studied. Aluminum is known as a potential contaminant during abrasive and/or slurry manufacturing processes. Known defect free slurries were doped with aluminum and effects on particle aggregation were observed. Specifically, it is of interest to identify the metrology and techniques that may be useful (and those that are not) in monitoring aluminum induced aggregation.