bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rare Earth Ion Implantation for Silicon Based Light Emission: From Infrared to Ultraviolet
Authors: Skorupa W. , Sun J. M. , Prucnal S. , Rebohle L. , Gebel T. , Nazarov A.N. , Osiyuk I.N. , Dekorsy T. , Helm M. 
Published: June 2019

AbstractUsing ion implantation different rare earth luminescent centers (Gd3+, Tb3+, Eu3+, Ce3+, Tm3+, Er3+) were incorporated into the silicon dioxide layer of a purpose-designed Metal Oxide Silicon (MOS) capacitor with advanced electrical performance, further called a MOS-light emitting device (MOSLED). The silicon dioxide layer did not contain silicon nanoclusters. Efficient electroluminescence was obtained from UV to infrared with a transparent top electrode made of indium-tin oxide. The electroluminescence properties were studied with respect to the luminescence spectra, decay time, impact excitation, cross relaxation (Tb3+), and power efficiency. Top values of the efficiency of 0.3 % corresponding to external quantum efficiencies well above the percent range were reached. The electrical properties of these devices such as current-voltage and charge trapping characteristics, were also evaluated. Moreover, we demonstrate photo- and electroluminescence in correlation to charge trapping characteristics for Er-rich MOSLEDs with a varying silicon cluster content. Finally, application aspects to the field of biosensing will be discussed.
Characterization of Er/O-doped Si-LEDs with Low Thermal Quenching
Authors: Karim A. , Ni W.-X. , Elfving A. , Persson P.O.Å. , Hansson G.V. 
Published: June 2019

AbstractElectroluminescence studies of MBE-grown Er/O-doped Si-diodes at reverse bias have been done. For some devices there is much reduced thermal quenching of the emission at 1.54 νm. There are examples where the temperature dependence is abnormal in that the intensity for a constant current even increases with temperature up to e.g. 80 °C. These devices have been studied with cross-sectional transmission electron microscopy to see the microstructure of the Er/O-doped layers as well as the B-doped SiGe-layers that are used as electron emitters during reverse bias. Although there are defects in the layers there is no evidence for large thick precipitates of SiO2. While reduced thermal quenching often is attributed to having the Er-ions within SiO2 layers, this is not the case for our structures as evidenced by our TEM-studies. The origin of the abnormal temperature dependence is attributed to the two mechanisms of breakdown in the reverse-biased diodes. At low temperature the breakdown current is mainly due to avalanche resulting in low-energy electrons and holes that quenches the intensity by Auger deexcitation of the Er-ions. At higher temperature the breakdown current is mainly phonon-assisted tunneling which results in a more efficient pumping with less de-excitation of the Er-ions. Finally at the highest temperatures the thermal quenching sets in corresponding to an activation energy of 125 meV, which is slightly lower than 150 meV that has been reported in other studies.
Gallium Oxide as a Host for Rare Earth Elements
Authors: Muth J. F. , Gollakota P. , Dhawan A. , Porter H. L. , Saripalli Y. N. , Lunardi L.M. 
Published: June 2019

AbstractPulsed Electron Beam Deposition (PEBD) and Pulsed Laser Deposition (PLD) were used to grow Gallium Oxide (Ga2O3) thin films on double sided polished sapphire substrates. At 850°C substrate temperature, smooth single crystal β-Ga2O3 films were obtained, which were confirmed with measurements by AFM of RMS surface roughness of about 1 nm. When characterized under electron beam excitation, the films exhibited different responses. For example: Europium doped films emitted intense red emission from 5D0 to 7Fj transitions while exhibiting weak broad emission from 300 to 500 nm. In contrast, Erbium doped films emitted strong emission from 300 to 500 nm peaked at 360 nm that was attributed to defects in the host matrix. Green emission from the Erbium transitions was observed at 528 and 550 nm. Films with different rare earth compositions varying from 0.1 % to 0.4 % were also prepared.High quality natural waveguides were formed with the deposited Ga2O3 films on the lower refractive index substrate sapphire. This was confirmed by measuring the refractive index by prism coupling and sharp coupling spectra.
Role of Molecular Structure of Complexing/Chelating Agents in Copper CMP Slurries
Authors: Patri Udaya B. , Pandija S. , Babu S.V. 
Published: June 2019

AbstractThe role of the molecular structure - different functional groups, the length of the carbon chain and the relative positions of different functional groups – of several complexing/chelating agents (acetic acid, glycine, ethylene diamine, succinic acid, alanine and amino butyric acid (ABA)) in controlling copper (Cu) removal rates was investigated. The results are consistent with the known activity of –COOH groups at acidic conditions and that of –NH2 groups in an alkaline environment. In comparison with glycine, it was also observed that an increase in the carbon chain length increased the removal rates at acidic pH values and decreased the removal rates at alkaline pH values. Also, Cu removal rates decreased with an increase in the distance between the –NH2 and –COOH groups in an amino acid at all pH values except at 4.
Effect of Temperature on Defect Generation during Copper Chemical Mechanical Planarization
Authors: Mudhivarthi Subrahmanya , Zantyea Parshuram , Kumara Ashok , Shim Jeung-Yeop 
Published: June 2019

AbstractChemical Mechanical Planarization (CMP) is the process of choice for planarization of the constituent layers of the Multi Level Metallization schemes in modern Integrated Circuits. Besides having a lot of advantages, copper CMP process still needs significant process control to eliminate defects such as delamination, microscratches, dishing, erosion etc. In this research, effect of heat generated at the interface on the generation of CMP defects has been investigated. CMP of blanket and patterned samples has been carried out at two conditions of pressure x velocity values with varying slurry temperature. Post CMP metrology is carried out using Atomic force microscopy (AFM) in order to characterize the variation in scratch depth, dishing profile and non-uniformity in step coverage. Pictures of the patterned samples polished at different temperatures are captured using Optical Microscopy (OM) to study the dishing and dissolution of copper lines in greater detail. The primary goal of this study was to gain deeper understanding of the effect of heat generation and rise in temperature at the pad-wafer-slurry interface on CMP induced defectivity.
Abrasive Contribution to CMP Friction
Authors: Evans David R. , Oliver Michael R. 
Published: June 2019

AbstractFriction in the CMP process is a subject of ongoing interest. The sources of friction can be the viscosity of the slurry between the pad and wafer, as well as the physical contact between the pad asperities and the wafer. The contact between the pad and the wafer can be direct or also through slurry particles trapped between the pad asperity and the wafer. We measure the friction between the wafer and the pad by measuring the CMP table current and subtracting out the background level. This is done for different concentrations of silica abrasive between 0 and 13%, as well as for different pressures and table speeds. Two widely different types of silica particles used in CMP are spherical colloid particles and aggregated fumed particles. We also compare the resultant friction behavior by comparing the results for both types of particles. For different abrasive contributions, the friction measurements are compared to the CMP removal rates. This evaluation is also done with a stationary wafer carrier, so that the observed removal rate at a specific point on the wafer is proportional to the local pressure on the wafer. The wafer carrier used for these tests uses a gimbal design. In this case the pressure at the leading edge of the wafer is larger than that at the trailing edge. From these studies we find that, for gimbaled systems with grooved pads, the friction is primarily caused by pad-asperity contact, and the addition of slurry particles does significantly change the friction interaction in the CMP process. Further, the non-uniformity in friction across the wafer is controlled by the pad surface structure and mechanical design of the CMP tool.
The effect of pad conditioning on planarization characteristics of chemical mechanical polishing (CMP) with ceria slurry
Authors: Yamamoto Yuichi , Kozuki Takaaki , Shibuki Shunichi , Maeda Keiichi , Inoue Yasuaki , Tawara Shinji , Toge Naoki 
Published: June 2019

AbstractA ceria-based in-situ conditioning process was successfully developed. A new single layered metal bonded conditioner was developed to solve problems encountered in implementing ceria based in-situ conditioning process. The planarity was significantly improved compared with that of conventional Ni-plated in-situ conditioning.
Correlation of Defects on Dielectric Surfaces with Large Particle Counts in Chemical-Mechanical Planarization (CMP) Slurries Using a New Single Particle Optical Sensing (SPOS) Technique
Authors: Remsen Edward E. , Anjur Sriram P. , Boldridge David , Kamiti Mungai , Li Shoutian 
Published: June 2019

AbstractA dual-sensor single particle optical sensing method (SPOS) is described for the measurement of the large particle count (LPC) in fumed silica polishing slurries. LPC values were expressed on a silica sphere-equivalent diameter scale rather than a polystyrene latex-equivalent size basis. Linear correlations between LPC and scratch counts on SiO2 surface films for wafers polished under clean room and table-top CMP conditions are demonstrated. However, these correlations were obtained for a limited set of model slurries; and further investigation will be needed to assess the general applicability of dual-sensor SPOS for oxide scratch defect prediction in CMP slurries.
A Predictive Model for Controlling Wafer Level Polish Rate Uniformity in Oxide CMP
Authors: Merchant Tushar P. , Borucki Leonard J. , Lawing A. Scott , Banerjee Suman K. , Zabasajja John N. 
Published: June 2019

AbstractA stress based engineering model has been developed that predicts the removal rate profile across the wafer as a function of the principal and shear stresses on the wafer. The model reproduces the form of the radial variation in polish rate that is seen without back side air for the current set of consumable conditions and the changes in the polish rate profile that occur when back side air pressure is used on an IPEC-472 tool. The model which is GUI based and can be run in the fab, returns the optimum recipe setting to maximize polish rate uniformity based on the current tool performance. Implementing this model in production resulted in a 50% improvement in within wafer uniformity statistics.
A Dishing Model for STI CMP Process
Authors: Chang Shih-Hsiang 
Published: June 2019

AbstractIt is well known that oxide dishing occurring in STI CMP leads to considerable sidewall and edge-parasitic conduction. Thus, a closed-form solution for quantitative prediction of oxide dishing is needed. A contact-mechanics-based approach to describe the steady-state oxide dishing occurring in STI CMP process is presented. The theory is validated through comparison with experimental data in the literature. Once validated, the model is used to quantify the effect of pattern geometry on oxide dishing. It is shown that the predictions of the model agree reasonably well with the experimental results measured in overpolishing time.
On the Relationship of CMP Wafer Nanotopography to Groove-Scale Slurry Transport
Authors: Muldowney Gregory P. 
Published: June 2019

AbstractMaterial removal in CMP occurs during intervals of pad-wafer contact separated by intervals of non-contact. One predictable sequence of non-contact intervals for a fixed point on the wafer is the traverse of the pad grooves, during which the wafer surface is renewed with fresh chemistry and heat is conveyed away. It is well understood that good uniformity requires machine kinematics that expose all points on the wafer to the same total contact time, mean slurry concentration, and temperature. Less widely known is that coherent structures tens to hundreds of nanometers high and matching the pitch of the pad groove pattern may be formed on an otherwise planar wafer despite multiple rotary motions. This unexpected phenomena is of interest not only because it manifests the impact of grooves and transport at scales not easily studied, but also because shrinking device architectures will ultimately disqualify even nanoscale departures from planarity. Wafer polish experiments are conducted alternately using circular, Cartesian grid, and spiral groove patterns using specialized pad conditioning and CMP recipes to amplify groove-induced nanotopography. Polish results illustrate sharp patterns in finished wafers (visible to the naked eye) that should not survive dual-axis tool kinematics. Computational 3-D model results are then presented for transient slurry mixing in the pad-wafer gap of a 200-mm polisher using the same groove patterns. A direct correspondence is found between observed wafer nanotopography and predicted groove-scale slurry mixing dynamics. In particular, the surface structures are underpolished areas traceable to intervals of non-contact protracted by depleted polish chemistry that prevails in groove segments when oriented relative to the local pad and wafer motion in a way that suspends transverse mixing in the groove crosssection. The study conclusively defines the features required in a groove pattern and polish recipe to form coherent structures matching the groove pitch. As validation of the theory, a groove pattern expected to form no surface topography is defined, experimentally tested, and shown to perform as predicted. Findings are discussed in the context of next-generation pad grooving and texturing as required for progressively more demanding applications of CMP.
Frictional behavior and particle adhesion of abrasive particles during Cu CMP
Authors: Hong Yi-Koan , Han Ja-Hyung , Song Jae-Hoon , Park Jin-Goo 
Published: June 2019

AbstractThe friction behavior and adhesion of abrasive particles were experimentally investigated during Cu CMP process. The highest particle adhesion force was measured in alumina slurry without citric acid. However, the alumina slurry with addition of citric acid had the lowest particle adhesion due to the adsorption of citrate ions on the alumina surfaces. While citrate ions could be easily adsorbed on alumina particles, silica particle showed the least effect on adsorption in citric acid solutions. The magnitude of adsorptions of citrate ions on the particle surfaces had significant effect on frictional behavior as well as adhesion force. Higher particle adhesion force resulted in higher friction, particle contamination and scratches in CMP process. It indicates that the magnitudes of particle adhesions on wafer surfaces in slurries can be directly related to the frictional behavior during CMP process.
Study on the planarization behaviour of copper CMP utilizing a dense pattern and a global step
Authors: Bormann Tilo , Bartha Johann W. 
Published: June 2019

AbstractThe major aim of CMP is not the removal of excess material but the planarization of the surface. Therefore the determination of the planarization length appears to be more important than the removal rate itself. It has been shown, that the planarization length is not a constant process parameter, but is related to the removal respectively to the polish time in a square root behaviour. Founded on models proposed by Boning, Ouma, et. al. we applied a sequential polish on a single quasi infinite step. The resulting profile could be simulated by a sequential convolution of the surface contour with a Gaussian transfer function.To come closer to the situation on a chip pattern we investigated the planarization behaviour on a specific pattern of the MIT854AZ copper CMP test chip, where a large area of unpatterned surface touches a pattern with a specific constant density.The 200 mm wafer samples consisted of RIE structured oxide films covered with 850 nm ECD copper. The polish was performed on a standard semiconductor manufacturing tool, using a commercial consumables set. The surface profiles were determined by a high resolution profiler within the polishing sequence. The densely patterned areas are removed within a certain polishing time while the transition point between the unpatterned and patterned area appears as a global step. The deposited copper thickness is sufficient to study the contour evolution in both phases, before and after removal of the dense pattern. The paper presents the experimental results on the contour evolution for the patterned fields as well as the global step.
Effect of Slurry Temperature on Cu Chemical Mechanical Polishing with Different Oxidizing Agents
Authors: Mudhivarthi Subrahmanya , Kumar Ashok 
Published: June 2019

AbstractChemical Mechanical Planarization (CMP) has evolved as one of the most critical and significant process in the manufacturing of semiconductor devices. Copper has become the material of choice for the interconnect wiring. The effect of heat generation at the interface is realized to be significant on copper CMP process. The increase in the oxidation rate of the chemical reaction and viscoelastic properties of polishing pads due to increase in temperature at the surface results in increased removal rates and change in planarization performance. In this research, the effect of temperature on the CMP performance using two most common oxidizing agents, KIO3 and H2O2 has been investigated using the CETRTM bench-top CMP tester. The coefficient of friction at the interface of polishing using both the oxidizers at different temperatures was monitored. The generated surface roughness post CMP was evaluated for samples polished using different oxidizing agents at different slurry temperatures. The AFM study was carried out using Digital InstrumentsTM D3100 instrument. This study is aimed at understanding the effect of temperature on the CMP process performance and the relative sensitivity of two most common oxidizers used in copper CMP towards temperature.
Pattern Symmetry and CMP Process Simulation
Authors: Yoshida Takafumi 
Published: June 2019

AbstractThis paper reviews the effect of pattern symmetry on Chemical Mechanical Planarization (CMP) and proposes a methodology to reduce the computational time of the CMP process simulation based on the boundary element method (BEM). We focus on a unit field which generates the symmetry structures and we formulate the BEM field matrix by parallel translations and spin/flip operations. We also discuss the characteristics of the field matrix and demonstrate the applications of the methodology.
In-Situ Chronoamperometry for CMP Slurry Investigations
Authors: Zhang Jian , Grumbine Steven , Carter Phillip W. , Werts Thomas 
Published: June 2019

AbstractA new application of the electrochemical method, in situ chronoamperometry, has been developed and used as a tool for CMP slurry characterization. The measured current response, i, resulting from a small applied potential is fit to an exponential equation, i = io + A1exp(-t/tD). The fitting parameters serve as a measure of surface reactivity (io), surface film robustness (A1), and the kinetics of film formation (tD). A description of the method and correlations to polishing performance are discussed in this paper.
Strong Synergistic Effects between Ceria and Montmorillonite particles in Glass CMP Slurries
Authors: Fang Mingming , Ianiro Michael , Eisenhour Don , Onge Jason St. 
Published: June 2019

AbstractGlass substrate has superior shock resistance and higher stiffness for increased rpm and access time than Al/NiP substrate. The main barrier for the use of glass instead of Al/NiP in desktop computers has been the high cost of the glass substrate, which is mostly caused by its need for a long polishing time. Developing a glass CMP slurry that can deliver a higher polishing rate and fewer surface defects is a continuous challenge in the disk industry. We recently discovered that adding montmorillonite particles into a ceria-based glass CMP slurry can significantly increase the polishing rate without sacrificing the surface smoothness. It is the first time, to our knowledge, that this strong synergistic effect between ceria and montmorillonite particles was reported in the glass CMP area. Several physical properties of the ceria- montmorillonite slurries, such as viscosity, zeta potential, and particle size, are characterized in order to understand the mechanism of the synergistic effect.
The Adsorption Behaviors of Citric Acid on Abrasive Particles in Cu CMP Slurry
Authors: Kang Young-Jae , Hong Yi-Koan , Song Jae-Hoon , Kim In-Kwon , Park Jin-Goo 
Published: June 2019

AbstractThe interaction between Cu surface and abrasive particles in slurry solution was characterized. The adsorption behavior of the citrate ions was dependent on the pH of the slurry and the concentration of the citric acid. The adsorption of citrate ions generated a highly negative charge on the alumina surface and shifted isoelectric point (IEP) to lower pH values. The Cu removal rate of alumina slurry was higher than that of colloidal silica based slurry in the investigated pH ranges. Although lower friction forces of Cu were observed in alumina based slurry of pH 4, 6 and 8, a higher friction force was observed at pH 2. This high friction force was attributed to the positive zeta potential and greater adhesion force of particle. It indicates that the magnitudes of particle adhesions on Cu surfaces in slurries can be directly related to the frictional behavior during CMP process.
Advanced ELID Process Development for Grinding Silicon Wafers
Authors: Islam M. M. , Senthil Kumar A. , Balakumar S. , Lim H. S. , Rahman M. 
Published: June 2019

AbstractA completely new and novel electrolytic system, Injection Electrode (IE) assisted electrolysis, has been tried here to improve the quality of the silicon wafer surfaces generated by Electrolytic In-process Dressing (ELID) grinding process. The Experiments were conducted by varying the injection flow rate in order to perform extensive analysis on the effect of injection flow rate on the generated wheel surface condition and the consequent grinding performance. Experimental results showed that lower injection flow rate greatly improved the wheel surface condition resulting in superior ground surface qualities.
Technique for Studying Overcurrent Behavior in YBCO Coated Conductors Using a Localized Magnetic Field
Authors: Coulter J. Yates , Ashworth Stephen P. , Dowden Paul C. , Willis Jeffrey O. 
Published: June 2019

AbstractOver current stabilization of YBa2Cu30x (YBCO) coated conductor high temperature superconductor tape is required in most applications. The conductor must carry currents in excess of the critical current, Ic, without damage during over current events. Conductor damage is the result of joule heating and excessive temperature rise in regions with low Ic. We have developed and applied a measurement technique using a locally applied magnetic field with a high spatial gradient to define a small area over which the Ic is depressed. By measuring the voltage and temperature as a function of current, power dissipation and temperature rise were determined. Unstabilized conductors experienced thermal runaway and are easily damaged. Copper stabilizers applied by electroplating decreased dramatically the temperature rise and increased the level of power dissipation compared with the unstabilized conductor.