bluuebunny/crossref_metadata_2025_split huggingface dataset:
Antimony Clustering due to High-dose Implantation
Authors: Shibahara Kentaro , Onimatsu Dai 
Published: April 2011

AbstractAntimony implantation is a promising technique for fabricating ultra-shallow n+/p junctions for extensions of sub-100-nm n-MOSFETs. By increasing the Sb+ implantation dose to 6×1014 cm−2, sheet resistance (Rs) of an implanted layer was reduced to 260 /sq. for rapid thermal annealing (RTA) at 800°C. The obtained junction depth of 19 nm is suitable for sub-100-nm MOSFETs. However, the reduction in the sheet resistance showed a tendency to saturate. No pileup at the Si-SiO2 interface, which was the major origin of dopant loss in lower dose cases was, observed in Sb depth profiles in this case. However, in the case of 900°C RTA, Sb depth profiles indicated that Sb was nearly immobile in the region where Sb concentration exceeded 1×1020 cm−3. These results imply that the major limiting factor of Rs reduction under the highdose condition is Sb precipitation, which is different from the lower dose cases.
In-situ Growth and Growth Kinetics of Epitaxial (100) CoSi2 Layer on (100) Si by Reactive Chemical Vapor Deposition
Authors: Rhee Hwa Sung , Lee Heui Seung , Park Jong Ho , Ahn Byung Tae 
Published: April 2011

ABSTRACTUniform epitaxial CoSi2 layers have been grown in situ on a (100) Si substrate at temperatures near 600 °C by reactive chemical-vapor deposition of cyclopentadienyl dicarbonyl cobalt, Co(η5-C5H5)(CO)2. The growth kinetics of an epitaxial CoSi2 layer on a Si (100) substrate was investigated at temperatures ranging from 575 to 650 °C. In initial deposition stage, platelike discrete CoSi2 spikes were nucleated along the <111> directions in (100) Si substrate with a twinned structure. The discrete CoSi2 plates with both {111} and (100) planes grew into an epitaxial layer with a flat interface on (100) Si. For epitaxial CoSi2 growth on (100) Si, the activation energy of the parabolic growth was found to be 2.80 eV. The growth rate seems to be controlled by the diffusion of Co through the CoSi2 layer.
Development of a Post-Spacer Etch Clean to Improve Silicide Formation
Authors: Yeh Edward K. , Sengupta Samit S. , Gabriel Calvin T. 
Published: April 2011

ABSTRACTThe formation of a uniform, low-resistance silicide is dependent on the contamination level of the silicon surface upon which the Ti or Co is deposited. Contamination may be in the form of embedded carbon and fluorine residues from previous processing steps, such as the LDD spacer etch. The extent to which the spacer etch contributes impurities can be determined by making contact angle measurements; that is, measurement of the angle formed by a droplet of water placed on the wafer surface. A clean silicon surface provides a contact angle of > 70°, whereas a contaminated silicon surface produces contact angles down to only a few degrees. By using contact angle as a metric, a post-spacer etch clean was developed to remove impurities from the silicon surface without significant silicon loss. The clean procedure entails the use of a CF4/H2O plasma to treat the wafer directly after spacer etch. The clean process was then evaluated by the formation of a blanket Ti silicide followed by sheet resistance measurement. By using this cleaning process, a Ti silicide sheet resistance comparable to that formed on virgin silicon wafers was obtained on wafers that experienced the spacer etch. By comparison, wafers that were subjected to the spacer etch but not the post-spacer clean yielded a higher sheet resistance. Additional study of the post-spacer etch clean process revealed that oxide on the wafer (even the small amount formed during an O2-based resist ash process) can prevent the CF4/H2O plasma from cleaning the surface, perhaps by blocking H in the cleaning plasma from extracting C and other contaminants from the silicon surface. Co silicide formation is even more sensitive to surface impurities than Ti silicide. Using the same post-spacer etch clean, uniform, low-resistance Co silicide formation has been demonstrated.
In situ and Ex situ Measurements of Stress Evolution in the Cobalt-Silicon System
Authors: Lucadamo G. , Lavoie C. , Cabral C. , Carruthers R. A. , Harper J.M.E. 
Published: April 2011

ABSTRACTThe biaxial stress in Co thin-films has been investigated in situ by measuring changes in substrate curvature that occurred during deposition and annealing.Films of Co, 35 to 500 nm in thickness, were deposited by UHV magnetron sputtering at room temperature on Si (100) and poly-Si substrates.Results show that during Co deposition the bending force increased linearly with film thickness; a signature of constant stress.In addition, the stress evolution during silicide formation was measured under constant heating rate conditions from room temperature up to 700°C. The stress-temperature curve was correlated with Co2Si, CoSi, and CoSi2 phase formation using in situ synchrotron X-ray diffraction measurements.The room temperature stress for the CoSi2 phase was found to be ∼0.8 GPa (tensile) in the films deposited on Si (100) and ∼1 GPa (tensile) on the films deposited on poly-Si.The higher tensile stress in the poly-Si sample could be a result of Si grain growth during annealing.
The Physical and Electrical Properties of Polycrystalline Si1−xGex as a Gate Electrode Material for ULSI CMOS Structures
Authors: Kang Sung-Kwan , Ko Dae-Hong , Ahn Tae-Hang , Joo Moon-Sik , Yeo In-Seok , Whoang Sung-Jin , Yang Doo-Young , Whang Chul-Joo , Lee Hoo-Jeong 
Published: April 2011

ABSTRACTPoly Si1−xGex films have been suggested as a promising alternative to the currently employed poly-Si gate electrode for CMOS technology due to lower resistivity, less boron penetration, and less gate depletion effect than those of poly Si gates. We investigated the formation of poly Si1−xGex films grown by UHV CVD using Si2H6 and GeH4 gases, and studied their microstructures as well as their electrical characteristics. The Ge content of the Si1−xGex films increased linearly with the flux of the GeH4 gas up to x=0.3, and saturated above x=0.45. The deposition rate of the poly Si1−xGex films increased linearly with the flux of the GeH4 gas up to x=0.1, above which it is slightly changed. The resistivity of the Si1−xGex films decreased as the Ge content increased, and was about one half of that of poly-Si films at the Ge content of 45%. The C-V measurements of the MOSCAP structures with poly Si1−xGex gates demonstrated that the flat band voltage of the poly Si1−xGex films was lower than that of poly-Si films by 0.2V.
Silicidation of Titanium-Rich Titanium Boride Deposited by Co-Sputtering on Si (100)
Authors: Sade G. , Pelleg J. 
Published: April 2011

ABSTRACTTitanium boride is known as a good diffusion barrier, in particular against copper, however outdiffusion of boron might deteriorate the semiconductor device. A TiSi2 sublayer prevents effectively boron penetration into the Si substrate. In this study the intention was to form a TiB2/TiSi2 bilayer film by silicidation of a titanium-rich titanium boride deposited by magnetron co-sputtering from elemental targets. The TiSi2 formation as well as the redistribution of titanium in the boride layer has been investigated by X-ray diffraction (XRD), Auger depth profiling and cross-sectional transmission electron microscopy (XTEM). Contact structure with Cu metallization was prepared to characterize this structure electrically.The Ti-rich titanium boride film was completely amorphous by XRD up to 700 °C. Crystallization of Ti-rich silicides (Ti3Si, Ti5Si3) have started at 750 °C, but already at 800 °C crystallization of C54 TiSi2 was completed. TiB2 begins to crystallize at 800 °C. Sheet resistance measurements confirmed these results. The sheet resistance of the as-deposited film was about 16 ω/□ and no significant change was detected up to 700 °C. Then, a remarkable drop in the sheet resistance to ∼1 Ω/□ was obtained after 800 °C, and this value was actually unchanged up to 925 °C. Cross-sectional TEM revealed the formation of the C54 TiSi2 layer between TiB2 and Si and additionally, a second C54 TiSi2 layer was observed within the boride film. Current-voltage measurements of the prepared contact structure showed that it was a Schottky diode with very high leakage current.
Controlling CoSi2 nucleation : the effect of entropy of mixing
Authors: Detavernier C. , Van Meirhaeghe R.L. , Maex K. , Cardon F. 
Published: April 2011

ABSTRACTIt is generally known that nucleation effects strongly influence the CoSi to CoSi2 phase transition. According to classical nucleation theory, the small difference in Gibbs free energy between the CoSi and CoSi2 phase is responsible for the nucleation barrier. Adding elements that are soluble in CoSi and insoluble in CoSi2 will influence the entropy of mixing, and thus change ΔG. In this way, the height of the nucleation barrier may be controlled.By depositing Fe or Ge (respectively replacing Co and Si in the CoSi lattice) in between the Co and the Si substrate, we were able to increase the nucleation barrier. In the presence of Ni, the nucleation barrier is lowered, and low-resistive disilicide is formed at lower temperatures.
Study of CoSix Spike Leakage for 0.1-um CMOS
Authors: Goto Ken-ichi 
Published: April 2011

ABSTRACTWe have clarified a new leakage mechanism in Co salicide process for the ultra-shallow junctions of 0.1-um CMOS devices and revealed the optimum Co salicide process conditions for minimizing the leakage current. We found that leakage currents generate from many localized points that are randomly distributed in the junction area, and not from the junction edge. We successfully verified our localized leakage model using Monte Carlo simulation. We identified abnormal CoSix spiking growth under the Co silicide film, as being the origin of the localized leakage current. These CoSix spikes grow rapidly only during annealing between 400°C and 450°C when Co2Si phase is formed. These spikes never grow during annealing at over 500°C, and decrease with high temperature annealing over 500°C. A minimum leakage current can be achieved by optimized annealing at between 800°C and 850°C for 30 sec. This is because a trade-off between reducing the CoSix spikes and preventing the Co atom diffusion from Co silicide film to Si substrate, which begins at annealing above 900°C.
The Effect of Wafer Shape on Slurry Film Thickness and Friction Coefficients in Chemical Mechanical Planarization
Authors: Lu Joseph , Coppeta Jonathan , Rogers Chris , Manno Vincent P. , Racz Livia , Philipossian Ara , Moinpour Mansour , Kaufmanc Frank 
Published: April 2011

ABSTRACTThe fluid film thickness and drag during chemical-mechanical polishing are largely dependent on the shape of the wafer polished. In this study we use dual emission laser induced fluorescence to measure the film thickness and a strain gage, mounted on the polishing table, to measure the friction force between the wafer and the pad. All measurements are taken during real polishing processes. The trends indicate that with a convex wafer in contact with the polishing pad, the slurry layer increases with increasing platen speed and decreases with increasing downforce. The drag force decreases with increasing platen speed and increases with increasing downforce. These similarities are observed for both in-situ and ex-situ conditioning. However, these trends are significantly different for the case of a concave wafer in contact with the polishing pad. During ex-situ conditioning the trends are similar as with a convex wafer. However, in-situ conditioning decreases the slurry film layer with increasing platen speed, and increases it with increasing downforce in the case of the concave wafer. The drag force increases with increasing platen speed as well as increasing downforce. Since we are continually polishing, the wafer shape does change over the course of each experiment causing a larger error in repeatability than the measurement error itself. Different wafers are used throughout the experiment and the results are consistent with the variance of the wafer shape. Local pressure measurements on the rotating wafer help explain the variances in fluid film thickness and friction during polishing.
Improvement of Wafer Edge Profile and Cmp Performance Through The Floating Head Design
Authors: Wang Huey-Ming , Moloney Gerry , Stella Mario , Deguzman Sesinando 
Published: April 2011

ABSTRACTThe dependence of IC fabrication on the Chemical Mechanical Planarization (CMP) process increases as the device features go down to 0.25 micron or beyond. Due to the tighter CMP process spec, it is very important to reduce the within wafer non-uniformity (WIWNU%) to achieve higher process yield. The symmetrical increment of linear velocity at wafer edge is not sufficient to change wafer edge profile by breaking the matched speed rule. A better solution is through the change of head design for a fixed platen from the polisher design point of view. This study demonstrates the improvement of the CMP process performance, especially at the wafer edge, from the modification of the floating type polish head. The best WIWNU% from a single air chamber head is about 5.12% at 6-mm edge exclusion (EE). In order to obtain better pad deformation control, the retaining-ring pressure chamber is separated from that of the sub-carrier. The average WIWNU% is about 4% for 3-mm and 5-mm EE from two-pressure-chamber head. Due to the limitation of retaining-ring pressure effect, a third pressure chamber is further added that can be extended the edge control up to 1 inch from the wafer edge. The WIWNU% is about 3.8% at 5-mm edge exclusion with low down forces. The slurry and insert types also show effect on the wafer edge profile. It has been also proven that this three-pressure-chamber head is able to reduce the post-CMP thickness variation from the ILD production wafer, especially at wafer edges. More detailed information and CMP mechanism will be discussed in this paper.
A New Poly-Si CMP Process with Small Erosion for Advanced Trench Isolation Process
Authors: Miyashita Naoto , Uekusa Shin-ichiro , Nishioka Takeshi , Iwami Satoko 
Published: April 2011

ABSTRACTChemical-Mechanical Polishing has been revealed as an attractive technique for poly-Si of trench planalization. Major issue of the process integration is pattern erosion after over polishing. A new process with silica slurry containing organic surfactant is reported in this paper. A patterned wafer after conventional CMP process is eroded by over polishing, however, the new process conducts small erosion for wide trenches. The organic surfactant is well known as a inhibitor for the protection of poly-Si from alkaline, and the new slurry shows a large pH dependency of the viscosity. The experimental work has been focused on the viscosity, and the mechanism of the small erosion is discussed. This new process should be useful for recessing poly-Si by CMP, because it keeps the erosion level very low.
Technique of surface control with the Electrolyzed D.I.water for post CMP cleaning
Authors: Shirakashi Mitsuhiko , Itoh Kenya , Katakabe Ichiro , Kamezawa Masayuki , Kihara Sachiko , Tsujimura Manabu , Saitoh Takayuki , Yamada Kaoru , Miyashita Naoto , Kodera Masako , Matsui Yoshitaka 
Published: April 2011

ABSTRACTChemical mechanical planarization (CMP) has been widely used for planarization of ILD, STI, plug and wiring processes. Wafer has several surfaces of materials, such as wiring materials, barrier materials, dielectric materials etc., that must be cleaned at the same time. In post metal CMP cleaning processes, in addition to cleaning several surfaces, it is very important that the oxidization level of metal materials, such as wiring, is held and controlled to maintain its resistance. Especially copper, that is began to use for wiring, is very easy to be oxidized. We have confirmed that the Electrolyzed D.I.water is effective in post Cu CMP cleaning for controlling the surface condition of Cu during cleaning and leaving a robust surface after CMP. We describe the Electrolyzed D.I.water system and present some result of analysis of Cu surface by treated with the Electrolyzed D.I.water.
Magnetoresistive properties of 1st AFM Co/Cu multilayers sputtered in an Ar+O2 atmosphere
Authors: Kubinski D. , Parsons M. , Hangas J. 
Published: April 2011

ABSTRACTSputter-deposited Co/Cu multilayers at the 1st antiferromagnetic maximum (tCu= 9Å) exhibit large magnetoresistance and low relative hysteresis and are attractive for use in many position sensor applications. Unfortunately, their large magnetoresistance values can be hard to reproduce, perhaps a consequence of the difficulties in growing flat, pin-hole free layers. In this study we demonstrate that their magnetoresistive properties can be improved with the addition O2 to the Ar sputtering gas. A sequence of [Co(15Å)/Cu(9Å)]20 multilayers were made using magnetron sputtering in a 2mTorr Ar+O2 atmosphere, with the O2 concentration ranging from <1 ppm to 10,000 ppm. For films sputtered in our purest Ar, the magnetoresistance was typically less than 10%. Adding small amounts of O2 to the Ar improved the magnetoresistance, and at 1000 ppm O2 concentration it reached an optimal value of ∼45% and was found to be quite reproducible. The largest saturation fields were also achieved at 1000 ppm O2. Increasing the O2 concentration beyond 1000 ppm degraded the magnetoresistance and reduced the saturation fields. Magnetic measurements indicate that the improved magnetoresistance for films sputtered in Ar + O2 is primarily a consequence of more complete antiferromagnetic ordering at low fields. Auger depth profiling revealed no evidence for the O2 incorporation into the films, even for those fabricated in 10,000 ppm O2. Influence of the O2 on the microstructure of the multilayers is discussed.
CVD of Thin Films of Copper and Cobalt from Different Precursors: Growth Kinetics and Microstructure
Authors: Mane Anil , Shalini K. , Devi Anjana , Lakshmi R. , Dharmaprakash M.S. , Paranjape Mandar , Shivashankar S.A. 
Published: April 2011

ABSTRACTWe have investigated the growth of thin films of Cu and Co by CVD using the β-diketonate complexes of the metals, viz., the respective acetylacetonates, dipivaloylmethanates, and ketocarboxylates. Film growth rate was measured as a function of CVD parameters such as substrate temperature and reactor pressure. Film microstructure was examined by optical microscopy, XRD, SEM, and STM. Electrical resistivity was measured as a function of temperature and film thickness. It was found that film microstructure is a function of the molecular structure of the precursor and of the other growth parameters. For example, Cu films from Cu(II) ethylacetoacetate comprise uniform, fine grains which result in bulk electrical conductivity at a thickness as small as 75nm. Though grown under nearly the same conditions, Cu films from Cu(II) dipivaloylmethanate are porous, with faceted, large crystallites. Cobalt films from Co(II) acetylacetonate are x-ray amorphous even at a deposition temperature of 450°C. It is possible, by choosing CVD parameters, to obtain metal films with microstructures appropriate to devices and to structures of very small dimensions.
X-ray Probes of Magnetic Multilayer Structure
Authors: Tanner B.K. , Hase T.P.A. , Fulthorpe B.D. , Clarke J. , Luo G.M. , Halder S.K. , Rozatian A.S.H. , Wilkins S.B. 
Published: April 2011

ABSTRACTWe discuss the application of x-ray scattering and fluorescence to the problem of unravelling the relationship between the structural and magnetic properties of magnetic multilayers. Particular attention is paid to the use of grazing incidence diffuse scatter to determine the compositional gradient, out-of-plane roughness amplitude, in-plane correlation length and fractal parameter of buried interfaces. Anomalous scattering provides information on the local environment of specific atoms and grazing incidence fluorescence is a depth -sensitive probe of chemical composition. We present examples indicating the sensitivity limits and the reproducibility of the techniques, all from multiple layer structures of magnetic metals.
Grain Boundary Curvature in Polycrystalline Metallic Thin Films
Authors: King Alexander H. , Mangat Rakesh , Owusu-Boahen Kwame 
Published: April 2011

ABSTRACTWell-annealed thin films are typically observed to exhibit mean grain diameters that are approximately equal to the film thickness. The standard explanation of this “sheet thickness effect” is that it results from a balance of grain boundary curvature in two different directions which, in turn, results from pinning at grain boundary grooves. TEM experiments have been performed to assess this model, and it is found that the predicted curvature about axes in the film plane is absent. Alternate explanations of the sheet thickness effect are considered.
Shape Transition of InAs Islands on InP (111)A
Authors: Li Hanxuan , Daniels-Race Theda , Hasan Mohamed-Ali 
Published: April 2011

ABSTRACTAtomic force microscopy (AFM) reveals that InAs islands grown on InP (111)A, as they grow in size, undergo a shape transition. Below a critical size of around 30 nm, round-shaped quantum dots form, while above this size they grow in the shape of triangles, reflecting the symmetry of the (111) substrates. The edges of triangular islands are aligned along the three equivalent {110} directions of the InP (111) surface. The triangular islands grow laterally much faster than vertically, indicating the aspect ratio decrease of the islands with increasing InAs coverage. Our results provide a better understanding of the self-organization behaviors of InAs on InP (111)A.
Carbon-Induced Ge Islands on Si(001) Grown by LPCVD
Authors: Goryll M. , Vescan L. , Lüth H. 
Published: April 2011

ABSTRACTThe formation of carbon-induced Ge islands has been studied using low-pressure chemical vapour deposition (LPCVD) of Ge on Si(001) at temperatures between 600°C and 700°C. Propane (C3 H8 ) diluted in He was used as a carbon source. The experiments show that the influence of carbon was most significant for deposition at low growth temperature of the Ge island layer. Small-sized islands with a narrow size distribution could be achieved using a carbon adsorption layer. Compared to a sample grown without this layer, the size distribution was significantly smaller. An enhancement of the growth rate of Ge, as seen from Rutherford backscattering spectroscopy (RBS) will be discussed.
Stability of Ensembles of Ge/Si(100) Islands
Authors: Zhang Y. , Drucker Jeff 
Published: April 2011

ABSTRACTWe have investigated the stability of ensembles of Ge/Si(100) islands by annealing at their growth temperature. Islands grown by molecular beam epitaxy at temperatures of 450, 550, 600 and 650°C were annealed for times between 5 and 120 minutes. Small, pure Ge hut clusters, bound by {105} facets appear to be extremely stable structures, surviving the longest anneals with no apparent coarsening. Dome clusters, however, coarsen. Large alloyed hut clusters, apparent in as-grown samples only for growth temperatures greater than 600°C, appear during annealing at 450 and 550°C. During anneals at 550 and 650°C, we observe novel coarsening behavior. Arrays of crystallographically oriented, alloyed hut clusters are formed which result from the dissolution of large, alloyed dome clusters.