bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Neutron Transmutation Doping on Optical Properties of Ge nanocrystals Prepared by Ion implantation
Authors: Dun Shaobo , Lu Tiecheng , Hu Qiang , Huang Ningkang , Zhang Songbao , Tang Bin , Dai Junlong , Resnick Lev , Shlimak Issai , Zhu Sha , Wei Qiangmin , Wang Lumin
Published: April 2011

Ge nanocrystals embedded in an amorphous SiO2film on Si matrix were prepared by ion implantation and subsequent annealing. Neutron transmutation doping (NTD) technique was used for doping Ge nanocrystals with As impurities. The microstructure, phase and photoluminescence of NTDed Ge nanocrystals were analyzed and compared with undoped Ge nanocrystals. A new photoluminescence peak related to As impurities was found. It is discovered that impurities are expelled from larger clusters resulted from Ge nanocrystal aggregation on the sample surface. To prevent nanocrystal aggregation and assure uniform doping of As, it is necessary to adopt appropriate implantation and annealing conditions.
Deposition energy dependence in cluster-assembled thin film densities
Authors: Meinander Kristoffer , Clauss Tina , Nordlund Kai
Published: April 2011

Mechanical properties of thin films grown by nanocluster deposition are highly dependent on the energy at which the clusters are deposited. Using molecular dynamics computer simulations we have quantitatively studied variations in the properties of copper thin films grown by deposition of Cu nanoclusters, at energies ranging from 5 meV to 10 eV per cluster atom, on a Cu (100) substrate.
Redistribution of Mn upon Annealing in Ferromagnetic Mn-implanted Si
Authors: Bolduc Martin , Awo-Affouda Chaffra , Ramos Frank , LaBella Vincent P
Published: April 2011

The redistribution of implanted Mn ions in Si after thermal annealing is studied. P-type Si wafers were implanted with 300-keV Mn+ ions at 350°C to a dose of 1×1015 cm-2, and then annealed at 800 °C for 5 min. Ferromagnetic hysteresis loops were obtained at 10 K using a SQUID magnetometer both before and after annealing. The saturation magnetization increases by ∼2 × after the post-implant annealing, while the Mn redistributes with sharp peaks in concentration. The calculated point-defect profile created during the implantation process peaks around the Mn-depleted region, suggesting that the residual implant damage may play a role in the ferromagnetic behavior of Mn-implanted Si.
An Exploration of Microscopy for Educational Applications in the High School Classroom
Authors: Fitzsimmons Ryan , Koekkoek Robert , Caragianis-Broadbridge Christine , Lehman Ann Hein , Cummings Karen
Published: April 2011

This project was initiated with an undergraduate student’s exploration of two advanced research tools: the scanning electron microscope (SEM) and the atomic force microscope(AFM). A research project was developed to study the application of microscopy to introductory physics instruction. Nine modules covering various aspects of introductory physics were created. Module components included discussions, laboratory experiments and assessments. Four of the nine modules were implemented in various high school classes. Assessments were used to compare student learning with the modules versus standard textbook/lecture techniques. Preliminary results of this study are presented along with recently developed methods created to facilitate implementation of these modules within the high school classroom.
Molecular Dynamic Computer Simulation of Thin Film's Heat Dissipation Rate
Authors: Cheng Ya-Yun , Hsieh Horng-Ming , Lee Cheng-Chung
Published: April 2011

Heat dissipation rate of the thin film is theoretically related to the thickness of the film. As the film grows on a substrate of constant temperature, the heat dissipation rate would be lower when the film becomes thicker. It is difficult to observe rate change during the film growth through experiment. With MD simulation, this rate can be "observed". A system including Platinum substrate at constant temperature 300K is setup. The constant temperature is obtained by Phantom method.

The average temperature of aluminum thin film is 600K. For various thickness of the film: 3.656nm, 5.302nm, and 7.567nm. The average temperature decays exponentially. Through the simple equation T=(T0-Ts)exp(-kt/d2PCp)+Ts, the dissipation rate should follow the parameter R=k/d2PCp and the parameter α=k/£Cp is the thermal diffusivity. It is observed that the thermal diffusivity increases with film thickness increases.
Thermal Conductivity and Natural Cooling Rate of Excimer-Laser Annealed SI: A Molecular Dynamics Study
Authors: Lee Byoung-Min , Seong Baek Seok , Baik Hong Koo , Munetoh Shinji , Motooka Teruaki
Published: April 2011

To investigate the relationship between the thermal conductivity and the cooling rate, we have performed molecular-dynamics (MD) simulations based on a combination of the Langevin and Newton equations to deal with a heat transfer from l-Si to c-Si. The thermal conductivity of c-Si was measured by the direct method. In order to deal with finite-size effects, different cell sizes perpendicular to the direction of the heat current were used. The values of the thermal conductivity of 58 W/mK and 35.7 W/mK in the Tersoff potential were obtained at 1000 K and 1500 K, respectively. A MD cell with a length of 488.75 ¡Ê in the direction of a heat flow was used for estimating the natural cooling rate. The initial c/l interface systems were obtained by setting the temperatures of the MD cell at 1000 K and 1500 K, respectively, for Z <= 35 ¡Ê and 3800 K for Z > 35 ¡Ê. During the natural cooling processes, the temperature of the bottom 10 ¡Ê of the MD cell was controlled. The cooling rates of 7.4 × 1011 K/sec for 1000 K and 5.9 × 1011 K/sec for 1500 K were obtained, respectively.
A Second Order Accurate Finite Difference Scheme for the Heat Equation on Irregular Domains and Adaptive Grids
Authors: Chen Han , Min Chohong , Gibou Frederic
Published: April 2011

We present a finite difference scheme for solving the variable coefficient heat equations with Dirichlet boundary conditions on irregular domains. A quadtree data structure is used to represent the non-graded adaptive Cartesian grids, and the interface is represented by the zero value points of the level set function. Numerical results in two spatial dimensions demonstrate second order accuracy for both the solution and its gradient.
Environment of Er Doped in a-Si:H and Its Relation with Photoluminescence Spectra
Authors: Kumeda Minoru , Sekizawa Yoshitaka , Morimoto Akiharu , Shimizu Tatsuo
Published: April 2011

The crystal-field potential at the Er3+ ion surrounded by six oxygen ions is expanded in terms of polynomials. After converting it into equivalent angular momentum operators, the Stark-splitting of the 4I15/2 ground state of the Er3+ ion is calculated. Influence of the change in the environment of the Er3+ ion on the shift of the energy levels is investigated and compared with the observed Er photoluminescence spectrum in a-Si:H. The scattering of the calculated energy levels by the structural fluctuation around the Er3+ ion is also compared with the linewidth of the component photoluminescence lines.
Role of Hydrogen in the Grain Growth in Microcrystalline Silicon Films
Authors: Lee Gye-Hyun , Yoon Jong-Hwan
Published: April 2011

Thick microcrystalline silicon (mc-Si:H) films were exposed to atomic hydrogen plasma at substrate temperature of 220°C after deposition. The microstructure of μc-Si:H films after exposure was characterized using Raman back scattering spectroscopy and transmission electron microscopy (TEM). Raman spectra reveal that the intensity near 520 cm−1 significantly increases after hydrogen exposure, indicating an increase of crystallinity in the films. TEM micrographs of μc-Si:H films exposed to atomic hydrogen also show an increase in the size of grains and a growth of crystalline grains ranging from surface to bulk. These results suggest that crystalline grain formation in μc-Si:H films is likely to be caused by chemical annealing.
Dielectric Functions of a-Si1-xGex:H versus Ge Content, Temperature, and Processing: Advances in Optical Function Parameterization
Authors: Podraza Nikolas J. , Wronski Christopher R. , Horn Mark W. , Collins Robert W.
Published: April 2011

We have applied an advanced model to analyze the dielectric functions e = e1 + ie2 of amorphous silicon-germanium alloys (a-Si1-xGex:H) (i) as a function of alloy content × by varying the flow ratio G = [GeH4]/{[SiH4]+[GeH4]} in plasma-enhanced chemical vapor deposition (PECVD), and (ii) for the first time as a function of the measurement temperature Tm by cooling the newly-deposited film. All e spectra (1.5 − 4.5 eV) have been measured by spectroscopic ellipsometry (SE) either in real time during deposition or in situ post-deposition in order to avoid surface contamination. From the resulting extensive database, the optical properties of the alloys can be predicted for any value × and Tm within the ranges of the database. Such a capability is expected to be useful, for example, in real time control of optical gap in the PECVD process and in predicting the quantum efficiency of multijunction a-Si:H-based solar cells versus operating temperature. The effect on the database of other deposition parameters such as the electrode configuration and the H2-dilution ratio R = [H2]/{[SiH4]+ [GeH4]} have also been explored. The latter two studies provide useful insights into materials properties that can be extracted from a single spectroscopic measurement performed in real time during PECVD. For example, the energy width of the resonance in e correlates closely with the precursor surface diffusion characteristics observed throughout growth -- both determined from real time SE. This result indicates that short-range ordering in the film is improved when surface diffusion is promoted.
High Efficiency Crystallization of Silicon Thin Films Using Continuous Wave Infrared Laser
Authors: Sano Naoki , Maki Masato , Andoh Nobuyuki , Sameshima Toshiyuki
Published: April 2011

Laser crystallization of silicon thin films on inexpensive glass substrates with a photo-absorption layer of diamond like-carbon (DLC) film was investigated. Scanned near-infrared beam emitted from a continuous wave (CW) laser diode at speed of 30 cm/s with power density of 30 kW/cm2 and wavelength of 940nm was effectively absorbed by DLC films, and changed to thermal energy for heating underlying silicon films with thickness of 50 nm. As a result, crystallization of silicon films was achieved. Raman scattering spectra was measure for the structural analysis of silicon films, and the sharp TO phonon peak at wave number of 520 cm-1 was observed. It shows that silicon films were effectively crystallized using the near-infrared laser diode. On the other hand, no crystallization was observed when the laser diode was directly irradiated to 50-nm-Si/quartz, because silicon has no optical absorption coefficient at 940 nm.
Polysilicon Films Formed On Alumina By Aluminium Induced Crystallization Of Amorphous Silicon
Authors: Pihan Etienne , Slaoui Abdelilah , Maurice Claude
Published: April 2011

We investigated the structural quality of polysilicon films fabricated by the aluminium induced crystallization (AIC) of amorphous silicon on alumina substrates. We analyzed the overall crystallographic quality of the poly-Si films in terms of grain size distribution and grain orientation versus crystallization temperature. For these studies, we used extensively the orientation imaging micrograph (OIM) technique, a very powerful tool that allows elucidating the inner-grain structure, the grain boundaries, the grain orientation. From our analysis, we may conclude that the polysilicon films formed by AIC on alumina substrates have the following features: (i) for all investigated temperatures, most of the silicon grains have a deviation angle from (100) crystallographic orientation between 5 and 25°; (ii) increasing the annealing temperature tends to decrease the (100) preferred orientation; (iii) the angular boundary distribution revealed that the main defects are those that have been observed inside isolated dentrites, namely low angle boundaries (<2°) and coincident site lattice boundaries such as Σ3, Σ9 and Σ27.
Epitaxial Silicon Thin Films by Low Temperature Aluminum Induced Crystallization of Amorphous Silicon
Authors: Sharif Khalil , Abu-Safe Husam H. , Naseem Hameed A. , Brown William D. , Al-Jassim Mowafak , Kishore Ram
Published: April 2011

Epitaxial silicon thin film growth has been achieved on crystalline silicon substrates using aluminum induced crystallization of amorphous silicon. The phenomenon of layer inversion has been utilized in this process. Silicon wafers <100> were used as the starting crystalline structure for the grown films. After the wafer is cleaned a thin layer of aluminum (300 nm) was deposited by sputtering. This deposition was followed by 300 nm film of amorphous silicon deposited using plasma enhanced chemical vapor deposition method. After annealing the samples for 40 minutes at 525 °C, a continuous film of silicon was formed on the silicon substrate. X-ray diffraction spectrum indicated that this film has the same orientation as that of the substrate. Scanning electron microscopy cross section images showed indistinguishable interface between the substrate and the crystallized film. Cross sectional transmission electron microscopy studies of the crystallized structure showed epitaxial nature of the films.
Fabrication of Poly-silicon Thin Films on Glass and Flexible Substrates using Laser Initiated Metal Induced Crystallization of Amorphous Silicon
Authors: Abu-Safe Husam , Naseem Hameed A. , Brown William D.
Published: April 2011

Poly-silicon thin films on glass and Kapton® substrates are fabricated using laser initiated metal induced crystallization method. Amorphous silicon films of 200 nm thickness were deposited on the two substrates. The films were capped with 200 nm aluminum films. The annealing laser was a cw Argon-ion laser system. Laser power densities ranging from 4 to 9 W/cm2 were used in the annealing process. The samples were irradiated for various periods of time. X-ray diffraction patterns from the initial results indicated the crystallization of the films. Scanning electron microscopy showed dendritic growth in the annealed samples. The composition analysis of the samples indicated aluminum-silicon alloy regions in the films.
Preparation of Large, Location-Controlled SI Grains by Excimer Laser Crystallization of α-SI FILM SPUTTERED AT 100°C
Authors: He Ming , Neihof E.J.J. , Andel Y. Van , Schellevis H. , Ishihara R. , Metselaar J.W. , Beenakker C. I. M.
Published: April 2011

Location-controlled grains with a diameter of 4 μm are successfully prepared by excimer laser crystallization of sputtered α-Si with μ-Czochralski (grain filter) process at a maximum processing temperature of 100°C. By a pulsed DC magnetron sputtering, α-Si film is deposited firstly on non-structured oxidized wafers for a test. It is found that a-Si film is easily ablated even with a low laser fluence when it is deposited with a substrate bias. From a non-biased sputtered α-Si precursor, grains with 1.8 mm in diameter can be prepared with excimer laser crystallization at room temperature. α-Si is then sputtered on the SiO2 with narrow holes (grain filters) and crystallized at room temperature. The location-controlled grains can be successfully prepared in a large energy density window. These location-controlled grains with a low temperature process are promising for single-grain thin film transistors (TFTs) on plastic substrate for an application to system integration on flexible microelectronics.
Thin-Film Polycrystalline-Silicon Solar Cells on Ceramic Substrates Made by Aluminum-Induced Crystallization and Thermal CVD
Authors: Gordon Ivan , Van Gestel Dries , Carnel Lode , Van Nieuwenhuysen Kris , Beaucarne Guy , Poortmans Jef
Published: April 2011

A considerable cost reduction could be achieved in photovoltaics if efficient solar cells could be made from thin polycrystalline-silicon (pc-Si) layers. Aluminum-induced crystallization (AIC) of amorphous silicon followed by epitaxial thickening is an effective way to obtain large-grained pc-Si layers with excellent properties for solar cells. To obtain efficient solar cells, the electronic quality of the pc-Si material obtained by AIC has to be optimized and the cell design has to be adapted to the material. In this paper, we report on pc-Si solar cells made by AIC in combination with thermal CVD on ceramic alumina substrates. We made pc-Si solar cells on alumina substrates that showed Voc values up to 533 mV and efficiencies up to 5.9%. This is the highest efficiency ever achieved with pc-Si solar cells on ceramic substrates where no (re)melting of silicon was used. We demonstrate that the quality of the pc-Si material can be improved drastically by reducing the substrate roughness using spin-on oxides. We further show that a-Si/c-Si heterojunctions lead to much higher Voc values than diffused homojunctions. A cell concept that incorporates spin-on oxides and heterojunction emitters is therefore best suited to obtain efficient pc-Si solar cells on alumina substrates.
Light Filtering Properties in a-SiC:H Multilayer Structures: A SPICE model
Authors: Martins J. , Vieira M. , Fernandes M. , Louro P. , Fantoni A.
Published: April 2011

A SPICE model of a-SiC:H/ a-Si:H pin/pin detector with voltage controlled spectral sensitivity is presented. The equivalent electric circuit able to describe the behavior of the multilayer structure under non-uniform illumination is composed of two series connected diodes, representing the pin structures, with two nonlinear current sources in parallel, representing the photogeneration for different steady state RGB illumination, with their value depending also on the thickness of the absorber layer and the built-in potential of the diodes. This device represents the 1D model of the LSP (Laser Scanned Photodiode) and may be interconnected in a 2D array trough resistors, modeling the high resistivity of the a-SiC:H layers. Electrical simulations were performed for different transducer configurations and illumination conditions and compared with the experimental data. The influence of the lateral and transverse resistors and built-in potential of the diodes on sensor parameters like spatial resolution, and signal amplitude are analyzed. A physical model supported by the electrical simulation gives insight into the methodology used for image representation and color discrimination.
Influence of Defect Post-deposition Treatments on poly-Si Thin-film Solar Cells on Glass grown by ECRCVD
Authors: Rau Björn , Schneider Jens , Conrad Erhard , Gall Stefan
Published: April 2011

The epitaxial thickening of a thin polycrystalline Si (poly-Si) film (seed layer) is a promising approach to realize an absorber layer of a poly-Si thin-film solar cell on glass. Such cell concept combines the benefits of crystalline Si and the high potential for cost reduction of a thin-film technology. Here, we discuss the influence of post-deposition treatments on the properties of absorber layers grown by electron-cyclotron resonance chemical vapor deposition (ECRCVD) and the solar cell performance, respectively. After the absorber growth and prior to the emitter deposition, defect annealing was used to improve the structural quality of the absorber layers and to increase the doping efficiency. For this, we used rapid thermal annealing (RTA) processes as well as thermal annealing in a conventional quartz furnace. In order to avoid damaging of the glass, only short annealing times (up to 400 s) were applied at temperatures of up to 950 °C. Defect passivation treatments were carried out at temperatures of about 350 °C to passivate the remaining defects in the films by hydrogen. The impact of both treatments on the solar cell parameter will be discussed. Excellent VOC's of up to 361 mV were achieved without hydrogenation showing the high potential of ECRCVD-grown absorbers. Applying both treatments resulted so far in an increase of VOC of about 400 mV. Because of the fact, that both post-treatments (particularly hydrogenation) are still not yet optimized, further improvements can be expected.
The Carbon Co-implant with Spike RTA Solution for Phosphorus Extension
Authors: Pawlak Bartek , Duffy Ray , Augendre Emmanuel , Severi Simone , Janssens Tom , Absil Philippe , Vandervorst Wilfried , Collart Erik , Felch Susan , Schreutelkamp Robert , Cowern Nick
Published: April 2011

As extensions have been up till now always used in N-MOS transistors with an activation anneal. Here, we show that also alternative doping by P can result in junction extensions that are extremely abrupt and shallow thus suitable for upcoming transistor technologies. P extensions are manufactured by amorphization, carbon co-implantation and conventional rapid thermal annealing (RTA). The impact of Si interstitials (Sii) flux suppression on the formation of P junction extensions during RTA is demonstrated. We have concluded that optimization of implants followed by RTA spike offers excellent extensions with depth Xj = 20 nm (taken at 5 × 1018 at./cm3), abruptness 3 nm/dec. and Rs = 326 Ω. Successful implementation of these junctions is straightforward for N-MOS devices with 30 nm gate length and results in an improved short channel effects with respect to the As reference.
Modeling and Simulation of the Influence of SOI Structure on Damage Evolution and Ultra-shallow Junction Formed by Ge Preamorphization Implants and Solid Phase Epitaxial Regrowth
Authors: Mok Caroline , Colombeau B. , Jaraiz M. , Castrillo P. , Rubio J. E. , Pinacho R. , Srinivasan M. P. , Benistant F. , Martin-Bragado I. , Hamilton J. J.
Published: April 2011

Preamorphization implant (PAI) prior to dopant implantation, followed by solid phase epitaxial regrowth (SPER) is of great interest due to its ability to form highly-activated ultra-shallow junctions. Coupled with growing interest in the use of silicon-on-insulator (SOI) wafers, modeling and simulating the influence of SOI structure on damage evolution and ultra-shallow junction formation is required. In this work, we use a kinetic Monte Carlo (kMC) simulator to model the different mechanisms involved in the process of ultra-shallow junction formation, including amorphization, recrystallization, defect interaction and evolution, as well as dopant-defect interaction in both bulk silicon and SOI. Simulation results of dopant concentration profiles and dopant activation are in good agreement with experimental data and can provide important insight for optimizing the process in bulk silicon and SOI.
Impurity Solubility and Redistribution Due to Recrystallization of Preamorphized Silicon
Authors: Duffy Ray , Venezia Vincent , Hopstaken Marco , Maas Geert , Dao Thuy , Tamminga Yde , Roozeboom Fred , van der Tak Karel
Published: April 2011

The use of silicon substrate preamorphization in ultrashallow junction formation has increased in recent years. The reduction of channeling during impurity implantation, coupled with higher-than-equilibrium metastable solubility levels, produces scaled junctions with low resistances. However, a number of physical phenomena arise that must be considered for proper impurity profile and device optimization.

With respect to impurity solubility advanced annealing techniques such as solid-phase-epitaxial-regrowth (SPER), flash, and laser annealing, can place impurity atoms on substitutional sites in the silicon lattice to extremely high concentrations when combined with preamorphization. In this context there is a relationship between the equilibrium distribution coefficient and metastable solubility. The long-established equilibrium distribution coefficient of an impurity, extracted in the liquid to solid phase transformation, can make a prediction of metastable solubility after transformation of amorphous silicon into crystalline silicon during SPER, flash, and laser annealing.

With respect to impurity redistribution the significant effects can be split into 3 categories, namely before, during, and after recrystallization. Before recrystallization impurity diffusion in the amorphous region may occur. Boron is particularly susceptible to this effect, which is very significant for the formation of p-type junctions. During recrystallization many impurities move ahead of the amorphous-crystalline (a/c) interface and relocate closer to the surface. In general redistribution is more likely at high impurity concentrations. For low-temperature SPER there is a direct correlation between the magnitude of this redistribution effect and the impurity metastable solubility. After recrystallization, with SPER, flash, and laser annealing commonly leaving residual damage in the silicon substrate, interstitial-diffusers are especially vulnerable to preferential diffusion toward the surface, where impurity atoms may be trapped, ultimately leading to a more shallow profile.
Deactivation of Ultra Shallow B and BF2 Profiles After Non-melt Laser Annealing
Authors: Sharp Jim , Cowern Nicholas E.B , Webb Roger P. , Giubertoni Damiano , Gennaro Salvotore , Bersani Massimo , Foad Majeed A. , Kirkby Karen J.
Published: April 2011

Ultra-shallow B and BF2 implants in silicon pre-amorphised with Ge have been activated using a scanning non-melt laser. The implants were activated either by using 1 or 10 laser scans. Isochronal 60s post-laser annealing between 700-1000°C were then undertaken to study the deactivation and reactivation of the B. Both B and BF2 samples were implanted with a dose of 1x1015 B cm-2 at an effective energy of 500eV. The presence of F from the BF2 implants, which is superimposed over the boron profile increases the sheet resistance of the initial fabricated junction (from 600-700 Ω/sq from B implants only to 750-1100 Ω/sq for BF2 implants). Fluorine also changes the deactivation and reactivation behaviour of the boron during the post-anneals by increasing the amount of deactivation of the boron.
Accurate Sheet Resistance Measurement on Ultra-Shallow Profiles
Authors: Clarysse Trudo H. , Moussa Alain , Leys Frederik , Loo Roger , Vandervorst Wilfried , Benjamin Mark C. , Hillard Robert J. , Faifer Vladimir N. , Current Michael I. , Lin Rong , Petersen Dirch H.
Published: April 2011

Comparison of state-of-the-art zero-penetration sheet resistance tools on ultra-shallow Boron CVD layers on top of a medium doped As layer.
Schottky-barrier height tuning using dopant segregation in Schottky-barrier MOSFETs on fully-depleted SOI
Authors: Knoch Joachim , Zhang Min , Zhao Qing-Tai , Mantl Siegfried
Published: April 2011

In this paper we demonstrate the use of dopant segregation during silicidation for decreasing the effective potential barrier height in Schottky-barrier metal-oxide-semiconductor field-effect-transistors (SB-MOSFETs). N-type as well as p-type devices are fabricated with arsenic/boron implanted into the device's source and drain regions prior to silicidation. During full nickel silicidation a highly doped interface layer is created due to dopants segregating at the silicide-silicon interface. This doped layer leads to an increased tunneling probability through the Schottky barrier and hence leads to significantly improved device characteristics. In addition, we show with simulations that employing ultrathin body (UTB) silicon-on-insulator and ultrathin gate oxides allows to further improve the device characteristics.
A Novel High-Stress Pre-Metal Dielectric Film to Improve Device Performance for sub-65nm CMOS Manufacturing
Authors: Teh Young Way , Sudijono John , Jain Alok , Venkataraman Shankar , Thirupapuliyur Sunder , Whitesell Harry
Published: April 2011

This work focuses on the development and physical characteristics of a novel dielectric film for a pre-metal dielectric (PMD) application which induces a significant degree of tensile stress in the channel of a sub-65nm node CMOS structure. The film can be deposited at low temperatures to meet the requirements of NiSi integration while maintaining void-free gap fill and superior film quality such as moisture content and uniformity. A manufacturable and highly reliable oxide film has been demonstrated through both TCAD simulation and real device data, showing ~6% NMOS Ion-Ioff improvement; no Ion-Ioff improvement or degradation on PMOS. A new concept has been proposed to explain the PMD strain effect on device performance improvement. Improvement in Hot Carrier immunity is observed compared to similar existing technologies using high density plasma (HDP) deposition techniques.
Process-Induced Strained P-MOSFET Featuring Nickel-Platinum Silicided Source/Drain
Authors: Lee Rinus Tek Po , Liow Tsung-Yang , Tan Kian-Ming , Ang Kah-Wee , Chui King-Jien , Guo Qiang-Lo , Samudra Ganesh , Chi Dong-Zhi , Yeo Yee-Chia
Published: April 2011

We report the use of nickel-platinum silicide (NiPtSi) as a source/drain (S/D) material for strain engineering in P-MOSFETs to improve drive current performance. The material and electrical characteristics of NiPtSi with various Pt concentrations was investigated and compared with those of NiSi. Ni0.95Pt0.05Si was selected for device integration. A 0.18 μm gate length P-MOSFET achieved a 22% gain in IDsat when Ni0.95Pt0.05Si S/D is employed instead of NiSi S/D. The enhancement is attributed to strain modification effects related to the nickel-platinum silicidation process.
Stress and Strain Measurements in Semiconductor Device Channel Areas by Convergent Beam Electron Diffraction
Authors: Li Jinghong , Domenicucci Anthony , Chidambarrao Dureseti , Greene Brian , Rovdedo Nivo , Holt Judson , Dunn Drerren , Ng Hung
Published: April 2011

Convergent electron beam diffraction (CBED) has been successfully applied to measure strain/stress in the channel area in PMOS semiconductor device with embedded SiGe (eSiGe) for 65nm technology. Reliable results of strain/stress measurements in the channel area have been achieved by good fitting of experimental CBED patterns with theoretical calculations. Stress measurements from CBED are in good agreement with simulations. A compressive stress as high as 823.9 MPa was measured in the <110> direction in the channel area of a PMOS device with eSiGe with 15% Ge and a thickness of 80nm. Stress measurements from CBED also confirm that the depth of the eSiGe and defects such as dislocation loops within the eSiGe relax strain/stress within the film and reduce strain/stress in the channel area.
A Physically Based Quantum Correction Model for DG MOSFETs
Authors: Karner Markus , Wagner Martin , Grasser Tibor , Kosina Hans
Published: April 2011

In this work we present a physically based quantum correction model for highly scaled double gate (DG) CMOS devices. In contrast to previous work, our quantum correction model is based on the bound states that form in the Si film. The Eigenenergies and expansion coefficients of the wave functions are tabulated for arbitrary parabolic approximations of the potential in the structure. This enables a highly efficient use for TCAD applications.
3D Modelling Of The Novel Nanoscale Screen-Grid FET
Authors: Ding Pei W. , Fobelets Kristel , Velazquez-Perez Jesus E
Published: April 2011

A novel field effect transistor (FET) that uses 3-dimensional (3-D) embedded gate fingers – the Screen-Grid Field Effect Transistor (SGFET) – is proposed. The gating action of the SGFET is based on the design of multiple gating cylinders into the channel region, perpendicular to the current flow. Such configuration allows a full 3-D gate control of the current which improves the device characteristics by increasing the gate to channel coupling. Initial investigations of the SGFET using 3-D TCAD TaurusTM simulation software are presented in this paper. The results indicate that the proposed SGFET offers the possibility of downscaling without degrading the output characteristics. A comparison between the SGFET and both bulk and SOI MOSFETs shows the superior characteristics of the SGFET for low power operation.
Characterization of Chemical Bonding in Low-K Dielectric Materials for Interconnect Isolation: A XAS and EELS Study
Authors: Hoffmann Patrick , Schmeisser Dieter , Engelmann Hans-Juergen , Zschech Ehrenfried , Stegmann Heiko , Himpsel Franz , Denlinger Jonathan
Published: April 2011

The use of low dielectric constant materials in the on-chip interconnect process reduces interconnect delay, power dissipation and crosstalk noise. To achieve the requirements of the ITRS for 2007-2009 minimal sidewall damage from etch, ash or cleans is required. In chemical vapor deposited (CVD) organo-silicate glass (OSG) which are used as intermetal dielectric (IMD) materials the substitution of oxygen in SiO2 by methyl groups (-CH3) reduces the permit-tivity significantly (from 4.0 in SiO2 to 2.6-3.3 in the OSG), since the electronic polarizability is lower for Si-C bonds than for Si-O bonds.

However, plasma processing for resist stripping, trench etching and post-etch cleaning removes C and H containing molecular groups from the near-surface layer of OSG. Therefore, compositional analysis and chemical bonding characterization of structured IMD films with nanometer resolution is necessary for process optimization.

OSG thin films as-deposited and after plasma treatment are studied using X-ray absorp-tion spectroscopy (XAS) and electron energy loss spectroscopy (EELS). In both techniques, the fine structure near the C1s absorption or energy loss edge, respectively, allows to identify C-H, C-C, and C-O bonds. This gives the opportunity to differentiate between individual low-k mate-rials and their modifications. The O1s signal is less selective to individual bonds. XAS spectra have been recorded for non-patterned films and EELS spectra for patterned structures. The chemical bonding is compared for as-deposited and plasma-treated low-k materials. The Fluo-rescence Yield (FY) and the Total Electron Yield (TEY) recorded while XAS measurement are compared. Examination of the C 1s near-edge structures reveal a modified bonding of the re-maining C atoms in the plasma-treated sample regions.
Theoretical Analysis of Thermal Conductivity in Amorphous Inter-layer Dielectrics
Authors: Shamsa Manu , Morrow Patrick , Ramanathan Shriram
Published: April 2011

Understanding thermal conduction in interlayer dielectrics (ILDs) is important for the optimal design of interconnect layers in backend semiconductor processing for future high-performance nano-scale devices. Reduced thermal conductivity of porous ILDs for example can adversely affect the temperature rise in the embedded metal lines leading to un-desirable reliability issues and design constraints. In this paper, we report results of our theoretical and experimental investigation of thermal transport in amorphous and porous dielectrics. A phonon-hopping model has been adapted to calculate the thermal conductivity in disordered materials. The value of hopping integral has been calculated by comparing the modeling results with experimental data for various amorphous and porous materials. The model shows reasonable agreement with experimental data for various amorphous materials including SiO2and other glasses over a wide temperature range from 50K – 300K. The model suggests that the hopping of localized high frequency phonons is a dominant thermal transport mechanism in such material systems.
Structures and Properties of an Ultra-Low-k Material: Classical-molecular-dynamics and First-principles Calculations
Authors: Ushio Jiro , Hamada Tomoyuki , Ohno Takahisa , Nakao Shin-Ichi , Yoneda Katsumi , Kato Manabu , Kobayashi Nobuyoshi
Published: April 2011

We determined the most probable atomistic structure of an ultra-low-k material (k≅ 2.5) by computer simulations. Among the candidate structures generated by a molecular-dynamics calculation, the most probable one that reproduces the observed properties was selected using a first-principles density-functional-theory calculation. The candidate structures consisted of Si-O-Si network with some silicon atoms, each of which had a CH3 group or a hydrogen atom bonded. The structure with CH3 groups but no hydrogen atom reproduced the experimental properties best. This structure was then used to investigate the behaviors of the material irradiated with ultraviolet light.
Thermal Oxidation of Ni and Co Alloys Formed by Electroless Plating
Authors: Gambino Jeff , Ivanov Igor , Mongeon Steve , Adams Ed , Hazel Scott , Meatyard Dave , Pokrinchak Phil , Chen Fen , DeHaven Pat , Kolics Artur , Polyanskaya Marina
Published: April 2011

The thermal oxidation of Co alloy and Ni alloy thin films on top of Cu, has been studied as a function of film composition. Four different alloys were studied; CoWP, CoWB, CoMoB, and NiMoB. For the Co alloys, significant oxidation is observed after an air anneal above 350C, accompanied by Cu diffusion through the film to the surface. In contrast, for the NiMoB films, there is minimal oxidation of the surface even after a 400C anneal in air, and Cu diffusion through the film is greatly reduced. These results indicate that Ni-based barriers may be desirable in applications where self-aligned metal layers are used on top of Cu interconnects as a replacement for dielectric caps such as SiN and SiCN.
Kinetics of Void Drift in Copper Interconnects
Authors: Choi Zung-Sun , Mönig Reiner , Thompson Carl V. , Burns Michael
Published: April 2011

We have observed the real-time behavior of electomigration-induced voids in both passivated and unpassivated copper interconnects in a Scanning Electron Microscope (SEM), and correlated void nucleation, growth, drift and stagnation with post-electromigration crystallographic microanalyses carried out using Electron Back-Scattered Diffraction (EBSD) analysis. Voids that nucleate at various locations along the interconnects often drift toward the cathode, where they grow, coalesce, and eventually cause electrical failure. In-situ SEM observations allowed for the tracking of void shapes and drift rates over long (multi-grain) distances. Changes in the size and the velocity of the voids were observed when the voids passed through different grains. These changes are attributed to the difference in diffusivity for different grain orientations. In passivated lines, voids were often trapped at individual grain boundaries, where they grew to cause failure, or de-trapped to continue to drift toward the cathode. In unpassivated lines, voids did not drift, but instead always nucleated and grew and grain boundaries. Locations at which voids grew in unpassivated lines, or at which voids were trapped and grew in passivated lines, were correlated with the crystallographic orientations of “upwind” and “downwind” grains. From these analyses, we find that the average electromigration interface diffusivities (z*D) as a function of grain orientation are ordered according to {100} > {111} > {110}. Quantitative analysis of void dynamics, correlated with crystallographic microanalyses, provides important data for modeling of electromigration-induced failure, and for process-optimization for improved reliability.
Comparison of Ru/Ta and Ru/TaN as Barrier Stack for Copper Metallization
Authors: Qu Xin-Ping , Tan Jing-Jing , Zhou Mi , Chen Tao , Ru Guo-Ping , Li Bing-Zong
Published: April 2011

The diffusion barrier properties for ultrathin Ru/Ta and Ru/TaN bilayer structure as the copper diffusion barrier are compared. Cu, Ru, Ta and TaN thin films are deposited by using the ion beam sputtering technique. The experimental results show that the thermal stability of the Cu/Ru/Ta or TaN /Si structure is much more improved than that of the Cu/Ru/Si structure without the interlayer. However, the Cu/Ru/TaN/Si shows better thermal stability than the Cu/Ru/Ta/Si structure, which should be attributed to the amorphous nature of the TaN interlayer. The microstructure evolution of the Cu/Ru/Ta (TaN)/Si structure during annealing is discussed. The results show that the Ru/TaN bilayer can be a very promising diffusion barrier in the future seedless Cu interconnect technology.
Low Temperature Plasma Etching of Copper for Minimizing Size Effects in sub-100 nm Features
Authors: Kulkarni Nagraj S , Tamirisa Prabhakar , Levitin Galit , Kasica Richard J , Hess Dennis W
Published: April 2011

A low temperature plasma etching process for patterning copper interconnects is proposed as a solution to the size effect issue in the resistivity of copper. Key features of this etching process based on a previous thermochemical analysis of the Cu-Cl-H system are discussed. Potential benefits of a subtractive etching scheme based on this process in comparison with the damascene scheme for copper-based interconnect processing in sub-100 nm features are presented in the context of the ITRS roadmap. Preliminary experimental work on plasma etching of Cu thin films using the proposed process is discussed.
Determination of Poisson's Ratio of Thin low-k Films using Bidirectional Thermal Expansion Measurement
Authors: Ye Jiping , Shimizu Satoshi , Sato Shigeo , Kojima Nobuo , Noro Junnji
Published: April 2011

A recently developed bidirectional thermal expansion measurement (BTEM) method was applied to different types of low-k films to substantiate the reliability of the Poisson's ratio found with this technique and thereby to corroborate its practical utility. In this work, the Poisson's ratio was determined by obtaining the temperature gradient of the biaxial thermal stress from substrate curvature measurements, the temperature gradient of the whole thermal expansion strain along the film thickness from x-ray reflectivity (XRR) measurements, and reduced modulus of the film from nanoindentation measurements. For silicon oxide-based SiOC film having a thickness of 382.5 nm, the Poisson's ratio, Young's modulus and thermal extension coefficient (TEC) were determined to be Vf = 0.26, αf =21 ppm/K and Ef =9,7 GPa. These data are close to the levels of metals and polymers rather than the levels of fused silicon oxide, which is characterized by Vf = 0.17 and Er = 69.6 GPa. The alkyl component in the silicon oxide-based framework is thought to act as an agent in reducing the modulus and elevating the Poisson's ratio in SiOC low-k materials. In the case of an organic polymer SiLK film with a thickness of 501.5 nm, the Poisson's ratio, Young's modulus and TEC were determined to be Vf = 0.39, αf =74 ppm/K and Er =3.1 GPa, which are in the typical range of V= 0.34~0.47 with E =1.0~10 GPa for polymer materials. From the viewpoint of the relationship between the Poisson's ratio and Young's modulus as classified by different material types, the Poisson's ratios found for the silicon oxide-based SiOC and organic SiLK films are reasonable values, thereby confirming that BTEM is a reliable and effective method for evaluating the Poisson's ratio of thin films.
The Role of Arginine as a Complexing Agent in Copper CMP
Authors: Moganty Surya Sekhar , Srinivasan Ramanathan
Published: April 2011

Chemical mechanical polishing (CMP) of copper was investigated in hydrogen peroxide and arginine slurries. Arginine was found to be a complexing agent for the copper in peroxide based slurries, in the alkaline region. The copper polish rate was measured in a Struers LaboPol-5 and LaboForce-3 CMP polishing tool. Static etch rate experiments of copper discs (25.4 mm Dia × 10 mm) were carried in 200 ml beakers with different combinations of hydrogen peroxide and arginine concentrations. Peroxide concentration was varied from 0 to 10 vol%, while the arginine concentration was varied from 0 to 1 wt% for both static etch and polish rate experiments. Fumed silica used as the abrasive medium for polishing.

The electrochemical processes involved in oxidative dissolution of copper were investigated by the Tafel corrosion plots and OCP measurements, using the Princeton Applied Research potentiostat. Three electrode corrosion flat cell was used for the electrochemical measurements. Corrosion current density and open circuit potentials (OCP) were used to elucidate the oxidative behavior of peroxide and the complexing role of arginine. Surface characteristics of the polished copper surface were analyzed with the Digital Instruments NanoScope AFM. Polishing with these chemicals resulted in smooth finish.

These results indicated that the arginine curtails the formation of oxidative layer on the copper surface and the removal rate was increased by forming complex with the copper.
A Novel Optical Technique to Measure Pad-Wafer Contact Area in Chemical Mechanical Planarization
Authors: Elmufdi Carolina L. , Muldowney Gregory P.
Published: April 2011

Real contact area between a CMP pad and wafer is a key factor in local contact pressure, friction and pad wear, all of which impact material removal and defect formation. A new optical method is introduced that quantifies the real contact area during polishing. Confocal reflectance interference contrast microscopy (C-RICM) uses a single focal plane to image the pad-wafer contact interface. A sapphire cover slip is used to provide optical transparency and to match the refractive index of the pad. Imaging the pad surface through the cover slip reveals areas of no reflection (pad-cover slip contact), areas of reflection (non-contact), and interference fringes (near contact). The C-RICM method was validated using micro-fabricated pads having uniform arrays of cylindrical surface structures of known contact area. Experiments conducted on porous polyurethane pads revealed that the real contact area is less than 10% of the total presented area. However Greenwood-Williamson (G-W) theory, widely used in CMP material removal models, predicts a contact area at least a factor of ten smaller. The discrepancy was found to result at least in part because the individual contact zones are not elliptical as assumed in G-W theory. In fact many contacting structures are crescents located at the perimeter of individual pores. These findings underscore the need for accurate control of pore density and morphology in polishing pads, in both initial manufacture and surface conditioning during CMP. The C-RICM method allows non-destructive benchmarking of polishing media in terms of pad-wafer contact, essential for developing improved pad architectures that achieve lower CMP defect levels.
Evaluation of Inhibitors for ECMP of Copper Using Electrochemical Quartz Crystal Microbalance (EQCM) Technique
Authors: Muthukumaran Ashok , Lowalekar Viral , Raghavan Srini
Published: April 2011

Chemical formulations for the electrochemical mechanical planarization (ECMP) of copper must contain constituents that are stable at anodic potentials. A key component of the formulation is a corrosion inhibitor, which is required to protect low lying areas while higher areas are selectively removed. Organic compounds, which adsorb on copper at low overpotentials and form a film by oxidation at higher overpotentials, may be particularly useful for ECMP. The objective of this work is to evaluate the effect of two inhibitors on copper dissolution in oxalic acid based systems using an electrochemical quartz crystal microbalance (EQCM) technique. By recording current as well as mass changes during the application of potential to electrodeposited copper films, the extent and mechanism of inhibition of sulfhydryl based acid (SBA) inhibitor has been explored.