bluuebunny/crossref_metadata_2025_split huggingface dataset:
Strong ultraviolet electroluminescence from porous silicon light-emitting diodes
Authors: Tam H. L. , Yuan J. , Li K. F. , Wong W. K. , Cheah K. W. 
Published: April 2011

ABSTRACTPorous silicon light-emitting diodes were found to emit strong line-shaped ultraviolet under a forward bias driving voltage of about 20 volts. The intensity was sufficiently strong to pump an organic crystal, Tb-dipicolinic acid, producing clear Tb 4f intra-shell transition photoluminescence spectrum. The current-voltage characteristics of the devices also showed negative differential resistance, which was frequency dependent. In addition, purging of the device with various gases could quench the electroluminescence but the intensity recovered partially after each purging, but with no change in emission spectrum. Both results indicate the transport was influenced strongly by local space charge. From the results, the electroluminescence mechanism is tentatively attributed to core recombination in the porous layer, and the spectral characteristics is due to the microcavity effect between the top Au contact and silicon substrate. The present study shows that porous silicon has the potential as UV source in optoelectronics applications.
Photoluminescence study of defects induced by B10H14 ions
Authors: Toyoda Noriaki , Aoki Takaaki , Matsuo Jiro , Yamada Isao , Wada Kazumi , Kimerling Lionel C. 
Published: April 2011

ABSTRACTDefect formation in Si by B10H14 (decaborane) ion implantation has been investigated with photoluminescence measurement. An intense W-line was observed at photon energy of 1.018eV from as-implanted FZ-Si by 30keV B10H14+ implantation. W-line center is considered as an interstitial aggregate and usually observed after ion implantation with subsequent low-temperatureannealing in the case of atomic ion implantation. As W-line is observed from as-implanted Si, the defect formation with B10H14 is expected to be different from that of B+ implantation with the same energy per atom. The energy dependence of W-line intensity is similar to that of diffusivity enhancement after rapid thermal annealing. Molecular dynamics simulation and Rutherford backscattering spectrometry channeling experiment suggest that one B10H14 implantation creates a larger number of dislocated Si atoms than that of B+ implantation with the same energy per atom. This characteristic of B10H14 implantation may cause the different defect reactions in subsequent annealing process.
Accurate Modeling of Residual recoil-mixing during SIMS Measurements
Authors: Yang Ming Hong , Odom Robert 
Published: April 2011

ABSTRACTSecondary ion mass spectrometry (SIMS) is an effective and powerful analytical technique, widely used in accurately determining dopant distributions (depth profiles). However, primary ion beam induced mass transport (ion mixing), especially the residual effect during SIMS profile measurements, greatly limits theaccuracy at nanometer depth resolutions by displacing and broadening the measured depth profile. In this paper, we present a simple deconvolution algorithm based on the general characteristics of the experimentally observed SIMS response function to reduce this broadening effect, thereby providing more accurate depth profiles. The results for several specific applications of this approach are presented and its strengths and limitations are discussed.
Characterization of Damage Induced by Cluster Ion Implantation
Authors: Aoki Takaaki , Matsuo Jiro , Takaoka Gikan 
Published: April 2011

ABSTRACTMolecular dynamics simulations of boron monomer and small clusters (B4 and B10) impacting on Si(001) were performed in order to investigate the damage formation by monomer/cluster impact. These monomer and clusters show similar implant depth and efficiency, but different damage structures. At the impact of B monomer with 230eV of incident energy, some point-defects such as vacancy-interstitial pairs are mainly formed. On the other hand B10 produces several times larger number of vacancies and interstitials compared with B1, This damage structure is different from one by B1 implantation and due to high yield amorphization of implanted region. This characteristic damage formation process is expected to cause different annihilation process.
A Comprehensive Model for Carbon Suppression of Boron Transient Enhanced Diffusion
Authors: Ngau Julie L. , Griffin Peter B. , Plummer James D. 
Published: April 2011

ABSTRACTIn this work, the time evolution of B transient enhanced diffusion (TED) suppression due to the incorporation of 0.018% substitutional carbon in silicon was studied. The combination of having low C concentrations, which reduce B TED without completely eliminating it, and having diffused B profiles for several times at a single temperature provides much data upon which various models for the suppression of B TED can be tested. Recent work in the literature has indicated that the suppression of B TED in C-rich Si is caused by non-equilibrium Si point defect concentrations, specifically the undersaturation of Si self-interstitials, that result from the coupled out-diffusion of carbon interstitials via the kick-out and Frank-Turnbull reactions. Attempts to model our data with these two reactions revealed that the time evolved diffusion behavior of B was not accurately simulated and that an additional reaction that further reduces the Si self-inter- stitial concentration was necessary. In this work, we incorporate a carbon interstitial, carbon substitutional (CiCs) pairing mechanism into a comprehensive model that includes the C kick-out reaction, C Frank-Turnbull reaction, {311} defects, and boron interstitial clusters (BICs) and demonstrate that this model successfully simulates C suppression of B TED at 750 °C for anneal times ranging from 10 s to 60 min.
A Quantitative Model of the Electrical Activity of Metal Silicide Precipitates in Silicon Based on the Schottky Effect
Authors: Tan Teh Y. , Plekhanov Pavel S. 
Published: April 2011

ABSTRACTA quantitative model of the electrical activity of metallic precipitates in Si is presented. An emphasis is placed on the properties of the Schottky junction at the precipitate-Si interface, as well as the carrier diffusion and drift in the Si space charge region. Carrier recombination rate is found to be primarily determined by the thermionic emission charge transport process across the Schottky junction rather than the surface recombination process. It is shown that the precipitates can have a very large minority carrier capture cross-section.
Influence of low thermal budget pre-anneals on the high temperature redistribution of low energy boron implants in silicon
Authors: Boucard F. , Schott M. , Mathiot D. , Rivallin P. , Holliger P. , Guichard E. 
Published: April 2011

ABSTRACTIt is now well established that the transient enhanced diffusion (TED) of ion implanted boron in silicon limits the formation of the ultra-shallow junctions required for the extreme deep sub- micron devices. It is also known that this TED is linked to the fate (elimination and agglomeration) of ion implantation related excess self-interstitials. Thus it can be expected that the final high temperature redistribution is at least partly governed by the effective initial point defect distribution at the onset of the high temperature plateau.In this contribution we present the experimental evidence that low thermal pre-anneals, by affecting the initial self-interstitials distribution, affects boron redistribution during a subsequent high temperature anneal. Samples implanted with high dose boron at 3 keV were first annealed at 700°C for various durations. These samples, as well as reference samples without the pre-anneal, were then RTA annealed at various high temperatures around 1000°C. The resulting B profiles were measured by SIMS. It is found that the pre-annealed samples exhibits a clear reduction of the TED as compared with the reference ones.
Resolving the Origin of a Cmp-Associated Yield/Reliability Issue “Center Spike”– Film Thickness Bulge in the Wafer Center. is CMP to Be Held Responsible for Its Appearance?
Authors: Wei David , Gotkis Yehiel , Boyd John , Kistler Rodney 
Published: April 2011

ABSTRACTA long-standing CMP related yield/reliability puzzle - film thickness spike, frequently appearing at the wafer center after it is processed by CMP, was studied. Optical film thickness measurements for pre- and post-CMP film were compared with surface topography profiles. Wafer surface profiles were also studied after the oxide film was HF-etched out. It was found that the post-CMP film thickness spike actually is not caused by CMP malfunctioning, but originates to a specific bare silicon wafer defect and occurs when the bare silicon wafer has a narrow dip-like defect (depression) in its center. The dielectric film, deposited over the wafer, follows the underlying center-dipped topography, and, being planarized by CMP, is transformed into a top-flat film with a thick pattern in the wafer center, filling the silicon dip. In-line and end-of-line yield related issues are discussed.
Synthesis of Model Alumina Slurries for Damascene Patterning of Copper
Authors: Lee Byung-Chan , Duquette David J. , Gutmann Ronald J. 
Published: April 2011

ABSTRACTModel alumina slurries for chemical-mechanical planarization (CMP) of copper have been studied using fundamental electrochemical concepts together with modification of surface tension and zeta-potential. A model slurry was established containing 3 wt% alumina (50 nm nominal size), 2 wt% potassium dichromate (K2Cr2O7) and 1 vol % DOWFAX, as abrasive, oxidizer and anionic surfactant, respectively, which resulted in blanket copper removal rates of 130 nm/min with smooth, low-particulate defect density surfaces without aggressive post-CMP cleaning. When used with a model silica-abrasive slurry to remove the Ta liner, well-defined damascene-patterned structures were achieved with low-particulate defect densities.Open circuit potential measurement, potentiodynamic polarization, surface tension measurement, and zeta-potential measurement were used in developing the model slurries. The variations obtained with alternative abrasives, alternative oxidizers and alternative surfactants illustrate the principles of synthesizing slurries for Cu and Ta.
Effect of Copper Film Surface Properties on CMP Removal Rate
Authors: Wang Yuchun , Bajaj Rajeev , Lam Gary , Dordi Yezdi , Bennet Doyle 
Published: April 2011

SummaryIt has been observed that CMP removal rate of copper varies for films from different sources. While the film hardness and static wet etch rate in the absence of inhibitors are similar for various films, the static etch rate in the presence of inhibitors is significantly different. Analysis by AFM, XPS, and ion beam sputtering showed the film roughness and surface composition were different for different Cu films within 160 angstroms of the surface. Thus the different in Cu CMP removal rates can be explained by a synergetic effect of copper film roughness (grain size), surface composition, and effective adsorption of inhibitors. This explanation suggests that if polishing is initiated by an aggressive polishing step, removal rate of the remaining bulk copper films become more consistent. Based on these findings, the polishing slurry and process were further optimized.
Analysis of CMP planarization performance for STI process
Authors: Tsujimura Manabu , Corporation Ebara , Ohta-ku Kamata , Japan Tokyo 
Published: April 2011

ABSTRACTIt has recently been reported that some waviness may affect STI CMP yield. CMP is designed primarily to planarize relatively with large r scale than small topography. However, there may be a range of wafer topographies in which STI patterns are over-polished, depending on peak-to-valley variations and frequencies. Permissible peak-to-valley variations and frequencies are calculated by determining whether the difference in polish quantities between the peak and valley is less than permissible values, such as 10 nm, 20 nm, and 30 nm. Reports indicate that slurry selectivity can decrease this effect, although with certain disadvantages.
Fixed Abrasive Technology for STI CMP on a Web Format Tool
Authors: Simpson Alexander , Economikos Laertis , Jamin Fen-Fen , Ticknor Adam 
Published: April 2011

ABSTRACTShallow trench isolation (STI) requires a high quality oxide with superior fill capability provided by High Density Plasma (HDP) oxide. Unfortunately, the HDP deposition process can create large within die topographies that are difficult to polish directly using conventional silica slurries. As a result, etch back integration schemes have traditionally been incorporated for STI polish. A more revolutionary approach is the use of Fixed Abrasive (FA) CMP [1]. FA CMP allows direct STI polish with good planarization/process stability, eliminating the need for prior etch back. The planarization efficiency is strongly dependent on the shape of the pad composites that hold the CeO2 mineral. Fixed abrasive pads with pyramid and pole shapes are available. In this work, three different fixed abrasive pads supplied by 3M corporation were evaluated for STI CMP polish performance using the Obsidian 8200C web format CMP tool. Basic polish characteristics such as planarity (dependence on sub-pad/pattern density), selectivity to topography, oxide dishing and nitride erosion are presented. The FA pads discussed here have been classified as “slow”, “medium” or “fast” depending on blanket oxide removal rate.The slow rate pad had a very high selectivity to topography and very low dishing of the down area oxide. The removal rate of blanket oxide was less than 100 Å/min. The pad was best suited to the polish of isolation trench structures with small, controlled overfill (> 200 Å) across the wafer. A large process window was demonstrated. The removal rate of the “medium” pad also decreased significantly at the onset of planarization with a blanket oxide removal rate of ca. 200 Å/min. Unlike the slow rate pad, the medium rate pad did not provide a suitable overpolish process window required for a manufacturable STI process. It is believed this pad would be a good choice for BPSG polish. In contrast to the slow and medium rate pads, the blanket oxide removal rate of the fast pad was ca. 2000 Å/min with no self-stopping capability at the onset of planarization. The removal rate was extremely center fast, such that it could not be compensated by adjustment of tool parameters. Use of a modified process developed within the DRAM development alliance (DDA) at East Fishkill (IBM/ Infineon) enabled the fast pad to polish deep STI structures that would otherwise be impossible using the slow or medium rate pads.
Modeling the Effects of Polishing Pressure and Speed on CMP Rates
Authors: Paul Ed 
Published: April 2011

ABSTRACTIn a previous CMP model, the effects of the slurry concentration of chemicals and abrasives on the polishing rate were quantitatively explained, for constant polishing pressure and velocity. That model is extended here to consider specific descriptions of mechanical abrasion, involving polishing pressures and speeds. Predictions of behavior are compared to literature data, leading to an improved understanding of the abrasive process in CMP.
Effect Of pH On Chemical-Mechanical Polishing Of Copper And Tantalum
Authors: Jindal Anurag , Li Ying , Babu S. V. 
Published: April 2011

ABSTRACTpH has a strong effect on the polish rates of copper (Cu) and tantalum (Ta) [1]. In this paper, removal rates of Cu and Ta using aqueous slurries containing alumina and silica abrasives in H2O2-glycine solution are studied at varying pH values. It is observed that variation in the Cu and Ta removal rates is a direct result of the change in surface characteristics of the films. Surface characteristics such as presence/absence of a passivating layer and hardness of such layer vary with pH and hence result in removal rate variation. It is also shown that a favorable Cu/Ta polish rate selectivity can be obtained by adjusting the pH of the slurry.
Photoacoustic spectra from copper phthalocyanine films on Si wafers
Authors: Ohmukai Masato , Kubota Hitoshi , Tsutsumi Yasuo 
Published: April 2011

ABSTRACTCopper phthalocyanine (CuPc) films were deposited on (100) silicon wafers by means of a vacuum evaporation method. We examined the films using photoacoustic (PA) spectroscopy to study their optical absorption properties. It was clarified that the PA signal from the silicon substrate can be excluded with a chopping frequency of 200 Hz when the film thickness is greater than 4.4 m. We detected an absorption band at 1.128 eV.
In Situ Biaxial Texture Analysis of Mgo Films During Growth on Amorphous Substrates by Ion Beam-Assisted Deposition
Authors: Brewer Rhett T. , Arendt Paul N. , Groves James R. , Atwater Harry A. 
Published: April 2011

ABSTRACTWe used a previously reported kinematical electron scattering model1 to develop a RHEED based method for performing quantitative analysis of mosaic polycrystalline thin film in-plane and out-of-plain grain orientation distributions. RHEED based biaxial texture measurements are compared to X-Ray and transmission electron microscopy measurements to establish the validity of the RHEED analysis method. In situ RHEED analysis reveals that the out-of-plane orientation distribution starts out very broad, and then decreases during IBAD MgO growth. Other results included evidence that the in-plane orientation distribution narrows, the grain size increases, and the film roughens as film thickness increases during IBAD MgO growth. Homoepitaxy of MgO improves the biaxial texture of the IBAD layer, making X-ray measurements of IBAD films with an additional homoepitaxial layer not quantitatively representative of the IBAD layer. Systematic offsets between RHEED analysis and X-ray measurements of biaxial texture, coupled with evidence that biaxial texture improves with increasing film thickness, indicate that RHEED is a superior technique for probing surface biaxial texture.
Study of Different Phases in a-C:H:N Thin Films Deposited by Plasma- Enhanced Chemical Vapour Deposition: A comparision Between Theoretical and Experimental Data
Authors: Antoniella F. , Valentini L. , Continenza A. , Lozzi L. , Santucci S. 
Published: April 2011

ABSTRACTThe electronic structure of amorphous carbon nitride (a-C:H:N) thin films prepared by radiofrequency (rf) plasma decomposition of CH4/N2 mixture was determined by soft x-ray photoe1ectron spectroscopy by the mean of synchrotron radiation source. On increasing N2 fraction, the valence band shows profound changes. The new features are identified by a comparison of the experimental spectra with theoretically weighted density of the states of graphite and C3N4 structures.
Diamond synthesis on oxide substrates
Authors: Hayashi Rie , Onishi Fumitomo , Takagi Yoshiki 
Published: April 2011

ABSTRACTRecently, many results were reported by many institutes and companies all over the world for diamond particles or thin films synthesized on crystalline substrates, such as molybdenum, silicon etc. But diamond on amorphous or oxide substrates, were rarely reported. In this study, we used material of amorphous and oxide for substrates, for example quartz glass, Alumina.We used unique apparatus of diamond synthesis. With our apparatus, completely closed system was used, no reaction gas was introduced to the chamber and no reactant gas was evacuated from it. We used graphite rod for heater and carbon source, at the same time.And we compared results with this unique closed system and with conventional flow system. Carbon sources of gaseous state (methane) and solid state ( graphite ), and closed and flow system result the deference of synthesized diamond particles.
Surface roughness control of the Al and Al2O3 thin films deposited by using pulsed DC magnetron sputtering
Authors: Qiu Jinjun , Li Kebin , Han Guchang , Guo Zaibing , Wu Yihong 
Published: April 2011

ABSTRACTThe thickness of the Al2O3 layer used in the magnetic tunneling junctions FM1/Al2O3/FM2 is less than 2 nm, here FM1 is for the ferromagnetic layer 1 and FM2 is for ferromagnetic layer 2. In order to obtain ultra-thin Al2O3 layer with higher breakdown voltage and pinhole free, extremely smooth surface roughness of this layer is required. The influence of the sputtering gas pressure, DC pulsed frequency, DC pulsed power, substrate bias and buffer layer on surface roughness and properties of Al thin films were studied. The single layer Al films are usually amorphous, texture (111) Al films can be obtained while using thin Ta 5 nm or Ta5/NiFe2 as underlayer. Very smooth Al thin film can be sputtered on Si/SiO2 (100) wafer with Ta/NiFe buffer layer at f=15 kHz (DC pulsed frequency) and with RF substrate biasing (Vpp is about 21 V). High quality MTJs with high MR ratio up to 44.6% and high field sensitivity up to 19.3%/Oe were finally demonstrated after optimization of thin film deposition process.
In-situ study of the stiffness of alumina thin films during vapor deposition
Authors: Proost Joris , Spaepen Frans 
Published: April 2011

ABSTRACTThe evolution of the biaxial modulus of amorphous alumina thin films has been studied insitu during electron-beam evaporation at 400°C on Si and sapphire substrates. A constant value of 197 ± 30 GPa was measured up to a thickness of 1.17 μm when depositing at 3 Å/s. This value was identical to that of films thinner than 0.30 μm deposited at an average rate of 6 Å/s. Above 0.30 μm, the modulus in these films decreased continuously to a value of 50 ± 8 GPa at a final thickness of 2.05 μm. Based on their refractive indices, the films deposited at 6 Å/s are 30% less dense than those deposited at 3 Å/s. This density deficit is insufficient to account for the modulus decrease; the remainder is probably the result of slit-like microcracks.
Calculations of Surface Structure for SrTiO3 Perovskite
Authors: Heifetsa E. , Eglitisb R.I. , Kotomin E.A. , Borstelb G. 
Published: April 2011

ABSTRACTWe present and discuss results of the calculations for SrTiO3 (100) surface relaxation with different terminations (SrO and TiO2) using a semi-empirical shell model (SM) as well as abinitio methods based on Hartree-Fock (HF) and Density Functional Theory (DFT) formalisms. Using the SM, the positions of atoms in 16 near-surface layers placed atop a slab of rigid ions are optimized. This permits us determination of surface rumpling and surfaceinduced dipole moments (polarization) for different terminations. We also compare results of the ab initio calculations based on both HF with the DFT-type electroncorrelation corrections, several DFT with different exchange-correlation functionals, and hybrid exchange techniques. OurSM results for the (100) surfaces are in a good agreement with both our ab initio calculations and LEED experiments.
Relation between texture and stress in thin sputtered molybdenum layers
Authors: van den Berk Ilse M. , Seijbel Léon J. , Delhez Rob 
Published: April 2011

ABSTRACTX-ray diffraction was used to measure the stress and the texture in thin molybdenum layers. The 500 nm thick layers were sputter deposited at various argon sputter pressures. All crystallites in the layers showed a strong tendency to develop a <110> direction perpendicular to the surface of the sample. Depending on the sputter pressure, a different fraction of the Mo crystallites developed a preference for a <110> direction parallel to the tangential direction of the rotating sputter table. The stresses found in the layer are best described when it is recognized that the crystallites in the layer belong to two groups: one group with both directions preferred and one group with only the out-of-plane direction preferred. For the intermediate sputter pressures the highest stresses were observed.