bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal and Stress Modeling for the Flash Lamp Crystallization of Amorphous Silicon Films
Authors: Smith Mark , McMahon Richard A. , Seffen Keith A. , Panknin Dieter , Voelskow Matthias , Skorupa Wolgang
Published: April 2011

Thin poly-crystalline silicon films are attractive for the fabrication of active matrix liquid crystal displays. We investigate the use of flash lamp annealing to crystallize amorphous silicon layers on glass substrates as a low cost manufacturing route. In this process amorphous silicon (a-Si) can be crystallized by solid phase crystallization (SPC) or in the super lateral growth (SLG) regime. We present a thermal model incorporating the phase transitions during annealing; providing a valuable tool for optimizing the process conditions. Another consideration is the evolution of stress resulting from the transient thermal loading of the substrate material. Results are presented for various substrate geometries and important scalability issues are addressed.
P Channel Mosfet Devices in Nanocrystalline Silicon
Authors: Panda Durga , Noack Max , Dalal Vikram
Published: April 2011

We report on the growth and properties of p-channel nanocrystalline Si thin film transistor (TFT) devices. In contrast to previous work, the devices are fabricated in n-body nanocrystalline Si. The doping of the n-body is systematically changed by doping with ppm levels of phosphorous. The threshold voltage was found to change systematically as phosphorus content increased. The TFT devices are of the bottom-gate type, grown on oxidized Si wafers. Source and drain contacts were provided by using either plasma grown p type nanocrystalline layers, or by the simple process of Al diffusion. A top layer of plasma-deposited silicon dioxide was found to decrease the off current significantly. High on-off current ratios exceeding 106 were obtained. Hole mobilities in the devices were consistently good, with the best mobility being in the range of ~1.3 cm2/V-s.
Boron Doped Polycrystalline Silicon Produced By Step-by-Step XeCl Excimer Laser Crystallization
Authors: Saleh Rosari , Nickel Norbert H
Published: April 2011

A series of boron doped polycrystalline silicon were produced using step-by-step laser crystallization process from amorphous silicon. The influence of doping concentrations on laser- induced dehydrogenation and crystallization of amorphous silicon and on hydrogen bonding have been investigated employing Raman spectroscopy and hydrogen effusion measurements. From hydrogen effusion spectra the hydrogen chemical potential is determined as a function of hydrogen concentration, which can be related to the hydrogen density-of-states distribution. The results from hydrogen effusion are consistent with the results obtained from Raman spectroscopy.
Temperature Dependence of Dark Current-Voltage Characteristics of Hydrogenated Amorphous and Nanocrystalline Silicon Based Solar Cells
Authors: Yan Baojie , Yang Jeffrey , Guha Subhendu
Published: April 2011

Systematic measurements of dark current density versus voltage (J-V) characteristics were carried out on a-Si:H, a-SiGe:H, and nc-Si:H solar cells at different temperatures from 23°C to 150°C. In a first order approximation, the dark J-V characteristics follow the standard diode characteristic formula for most high quality solar cells. The temperature dependence of the reverse saturation current can be used for deducing the intrinsic layer bandgap for the three types of solar cells. From a detailed analysis using the derivative of the measured dark J-V characteristics, we obtain different features in the plot of ideality factor versus bias voltage for the three types of solar cells. We also deduce the distribution of density of states using a recently proposed procedure [1]. In general, a peak near the middle of the bandgap appears for the three types of solar cells; below the middle of the bandgap, there is an exponential-like broad distribution of gap states. However, the calculated gap state distribution shows a temperature dependence, which may be caused by the simplification of the calculation procedure.
Enhanced Antimony Activation for Ultra-Shallow Junctions in Strained Silicon
Authors: Bennett Nick , Smith A. J. , Beer C. S. , O'Reilly L. , Colombeau B. , Dilliway G. D. , Harper R. , McNally P. J. , Gwilliam R. , Cowern N. E. B. , Sealy B. J.
Published: April 2011

Sheet resistance (Rs) reductions are presented for antimony and arsenic doped layers produced in strained Si. Results re-emphasise the Rs reduction for As comes purely as a result of mobility improvement whereas for Sb, a superior lowering is observed from improvements in both mobility and activation. For the first time, strain is shown to enhance the activation of dopant atoms whilst Sb is seen to create stable ultra-shallow junctions. Our results propose Sb as a viable alternative to As for the creation of highly activated, low resistance ultra-shallow junctions for use with strain-engineered CMOS devices.
Integration of Solid Phase Epitaxial Re-Growth, Flash and Sub-Melt Laser Annealing for S/D Junctions in CMOS Digital Technology
Authors: Severi Simone , Augendre Emmanuel , De Meyer Kristin
Published: April 2011

Several aspects of the integration of diffusion-less junctions in a NMOS and PMOS conventional flows are evaluated. Processes as Solid Phase Epitaxial Regrowth (SPER) or advanced annealing techniques, as flash or laser, demonstrates benefits not only on the 1D junction profiles but also on the transistor characteristics. An optimization of the implants and of the annealing conditions lead to improved or equivalent transistors performance and short channel effects control compared to the conventional spike RTA process. A significant gain in the overlap capacitance could allow for reduced CV/I. Furthermore the junction leakage can be lowered down to the values reached with the conventional spike RTA process.
Mechanisms for Interstitial-Mediated Transient Enhanced Diffusion of N-type Dopants
Authors: Harrison Scott Anthony , Edgar Thomas F. , Hwang Gyeong S.
Published: April 2011

As silicon transistor dimensions scale down, transient enhanced diffusion of n-type dopants has become a major barrier toward achieving required junction depths for transistors. In this paper, we use density functional calculations to identify a pathway by which silicon interstitials can mediate As and P diffusion. We show that As-silicon interstitial and P-silicon interstitial pairs in the neutral and negative charge states diffuse via a mechanism in which the dopant is bond-centered at energy minima and threefold coordinated at the high energy saddle point during dopant migration. For both As-silicon interstitial and P-silicon interstitial pairs, we conclude that the neutral pairs will dominate under intrinsic conditions while the neutral and negatively charged pairs will both contribute under heavily doped extrinsic conditions.
Ab-Initio Study of Boron Diffusion Retardation in Si1-xGex
Authors: Kim Yonghyun , Kirichenko Taras A. , Banerjee Sanjay K. , Hwang Gyeong S.
Published: April 2011

We study B diffusion in the presence of Ge by using a first principles density functional theory calculation. We investigate the relative stability and migration barriers of Si and Ge interstitials as well as binding energy and diffusion pathway of Boron-Interstitial (BI) pair comprised of Boron and Si or Ge interstitials. We find that Ge interstitials are more stable but less mobile compared to Si interstitials, leading to higher population of interstitials in the implanted Si1-xGex. However, BI pair comprised of Ge interstitial and Boron is less stable compared to Si interstitial –Boron pair and migration barrier of BI pair in presence of Ge is increased, leading to less TED.
Thermally Induced Deformation and Stresses During Millisecond Flash Lamp Annealing
Authors: Smith Mark , Seffen Keith A. , McMahon Richard A. , Anwand Wolfgang , Skorupa Wolgang
Published: April 2011

A flash lamp has been proposed for annealing wafers with diameters approaching 100 mm. The equipment applies a pulse, with duration 0.5 ms to 20 ms, resulting in large transient thermal gradients in the wafer. In this paper, we present a model for the thermal reaction of this process and its effect upon the mechanical behaviour, in order to predict stresses, shape changes and to capture practical phenomenon, such as bifurcation of deformation modes. We then use the model to follow changes in the expected response consequent on altering process conditions, as well as exploring important issues associated with scaling to large wafer sizes. The model is further used to predict material yielding leading to permanent deformations. This work presents the first description of the thermo-mechanical response of wafers to flash lamp annealing in the millisecond time regime and is therefore fundamental to the use of this technique in the fabrication of semiconductor devices.
Analysis and Optimisation of New Implantation and Activation Mechanisms in Ultra Shallow Junction Implants using Scanning Spreading Resistance Microscopy (SSRM)
Authors: Eyben Pierre , Severi Simone , Duffy Ray , Pawlak Bartek , Augendre Emmanuel , Vandervorst Wilfried
Published: April 2011

Within this paper we have demonstrated the unique capability of scanning spreading resistance microscopy (SSRM) in order to evaluate and optimize the recent approaches towards the formation of advanced p-MOS devices. As shown in this paper, such an optimization requires a detailed 2D-analysis on completely processed devices as two-dimensional interactions may cause (unexpected) lateral diffusion and (de) activation of underlying profiles. Emphasis will be on junction formation using Ge- pre-amorphization and carbon based cocktail implantation coupled with activation based on solid phase epitaxial regrowth and/or millisecond laser anneal. In the case of a Ge-pre-amorphization implant followed by solid phase epitaxial regrowth, SSRM shows an obvious relationship between the presence of defects in the end of range region and halo implant de-activation. Based on the quantified 2D-profiles we can extract the lateral and vertical junction depths as well as the lateral and vertical abruptness of the extension region. A drastic reduction of the lateral diffusion for the cocktail implant versus the standard reference devices with classical spike annealing is eminent. At the same an important reduction of the lateral diffusion of the source/drain implants (HDD) under the spacer can be seen. The SSRM results also highlight the impact of different activation mechanisms on the channel implants (in particular on the shape of the halo pockets).
Systematic Characterization of Pseudomorphic (110) Intrinsic SiGe Epitaxial Films for Hybrid Orientation Technology with Embedded SiGe Source/Drain
Authors: Ouyang Christine , Madan Anita , Klymko Nancy , Li Jinghong , Murphy Richard , Wildman Horatio , Davis Robert , Murray Conal , Holt Judson , Panda Siddhartha , Ieong Meikei , Sung Chun-Yung
Published: April 2011

PFET devices fabricated using embedded SiGe source/drain on (110) silicon substrates have shown significant performance improvement compared to PFETs with embedded SiGe on (100) SOI substrates. In this paper, we report a systematic material characterization on the epitaxial SiGe films, both on blanket and patterned substrates, and corresponding PFET performance data. The SiGe films were deposited in an RTCVD system. The epitaxial growth rate on (110) substrates was 30% lower than on (100), and 30% higher on patterned device wafers compared to blanket wafers. Films were characterized using an array of methods such as High Resolution XRD (for Ge composition, strain and thickness), Auger (for Ge composition), UV Raman microprobe (for strain), AFM (for surface morphology), and TEM (for epi quality). The Ge compositions determined by XRD and Auger are in excellent agreement (15~16%). The amount of strain extracted from the Raman measurements is also consistent with the amount determined by XRD, which is 0.60%, corresponding to a fully strained Si0.85Ge0.15 film. AFM showed much higher RMS and Rmax for the SiGe films on (110) substrates compared to those on (100) substrates. XTEM showed high crystalline quality with very low defect count in the SiGe source/drain and Si channel regions. PFETs with an embedded Si0.85Ge0.15 source/drain on hybrid orientation (HOT) substrates provided a 30% advantage in drive current and a 23% enhancement in ring oscillator speed compared to control devices on (100) SOI wafer.
Impact of Heavy Boron Doping and Nickel Germanosilicide Contacts on Biaxial Compressive Strain in Pseudomorphic Silicon-Germanium Alloys on Silicon
Authors: Chopra Saurabh , Ozturk Mehmet C , Misra Veena , McGuire Kris , McNeil Laurie
Published: April 2011

In recent years, the semiconductor industry has increasingly relied on strain as a performance enhancer for both n and p-MOSFETs. For p-MOSFETs, selectively grown SiGe alloys in recessed source/ drain regions are used to induce uniaxial compressive strain in the channel. In order to induce compressive strain effectively using this technology, a number of parameters including recess depth, SiGe thickness (junction thickness), sidewall thickness, dopant density, dislocation density, and contact materials have to be optimized. In this work, we have studied the effects of heavy boron doping and self-aligned germanosilicide formation on local strain. Raman spectroscopy has been used to study the impact of heavy boron doping on compressive stress in SiGe films. Strain energy calculations have been performed based on Vegard's law for ternary alloys and the effect of boron on strain in SiGeB alloys modeled quantitatively. It will be shown that, owing to the smaller size of a boron atom, one substitutional boron atom compensates the strain due to 6.9 germanium atoms in the SiGeB film grown pseudomorphically on silicon. The critical thickness of SiGeB has been calculated for the first time based on kinetically limited critical thickness calculations for metastable SiGe films. It will be shown that the critical thickness of the alloy increases as the boron content in the alloy is increased, making boron concentration an additional parameter for optimizing strain in the MOSFET. Based on these conclusions, boron concentration can be used to preserve the strain for thicker SiGeB films (compared to SiGe films) while keeping the dislocation density low. Furthermore, we show that NiSiGe contacts can have a profound impact on the SiGe strain. Our results indicate that NiSiGe introduces additional stress in the underlying SiGe, which further affects the strain induced in the channel
Using Quantitative TEM Analysis of Implant Damage to Study Surface Recombination Velocity in Silicon
Authors: Gasky Jennifer Lee , Morghem Sophya , Jones Kevin
Published: April 2011

Silicon wafers with shallow trench isolation structures 3700Å deep were self-implanted with silicon at 40keV, and a dose of 1E15/cm2. This produced an amorphous layer 1000Å deep. The samples were subsequently annealed at temperatures ranging from 750°C to 900°C. The excess interstitials can recombine at the “surface” created by the proximity to the trench sidewall. Plan-view TEM was used to quantify the dislocation distribution as a function of distance from the trench sidewall. It was found that there was no measurable change in defect density as a function of distance from the trench. This was true for both the 20 minute isochronal anneal, and the isothermal study 750°C. This suggests there is a relatively weak recombination of interstitials at the surface. This is surprising given most of the TCAD models assume a very fast surface recombination velocity.
Predictive Model for B Diffusion in Strained SiGe Based on Atomistic Calculations
Authors: Ahn Chihak , Song Jakyoung , Dunham Scott T
Published: April 2011

Using an extensive series of first principles calculations, we have developed general models for the change in energy of boron migration state via interstitial mechanism as a function of local alloy configuration. The model is based on consideration of both global strain compensation as well as local effects due to nearby arrangement of Ge atoms. We have performed KLMC (Kinetic Lattice Monte Carlo) simulations based on change in migration energy to explain the reduced B diffusion in strained SiGe and compared our results to experimental observations. These models include significant effects due to both global stress and local chemical effects, and accurately predict the B diffusivity measured experimentally in strained SiGe on Si as a function of Ge content.
TCAD Modeling and Simulation of Sub-100nm Gate Length Silicon and GaN based SOI MOSFETs
Authors: Ma Lei , Jin Yawei , Zeng Chang , Dandu Krishnanshu , Johnson Mark , Barlage Doug William
Published: April 2011

Sub-100nm gate length silicon and GaN based SOI n-type MOSFET are modeled and simulated using ISE-TCAD (now synopsys_sentaurus). Several silicon SOI structures such as planar fully depleted SOI, FinFET, Tri-Gate MOSFET, cylindrical channel (OMFET) and triangular channel MOSFETs have been studied to compare the structure dependence of the device performance. Silicon and GaN as channel materials are also compared for these different SOI structures for projecting the device performance for very short channel SOI MOSFETs. Our study shows that for sub-100nm gate length, GaN based transistors have better Ion/Ioff ratio and higher small signal transconductance than silicon based transistors. And GaN and Si based devices have comparable performance such as sub-threshold slope and threshold roll off, etc. However for sub 20nm gate length, simulation shows that while it is not satisfying for silicon based device for digital applications, GaN based transistors with lower off state leakage current, less short channel effect than Silicon based transistors are still good candidates for digital applications . The TCAD study shows that GaN could be a promising candidate for making very short channel device as the GaN processing technology is advancing.
Film Characterization of Ultra Low-k Dielectrics Modified by UV Curing with Different Wavelength Bands
Authors: Matsuura Masazumi , Goto Kinya , Miura Noriko , Hashii Shinobu , Asai Koyu
Published: April 2011

This paper describes film characterization of Ultra Low-k (ULK) dielectrics modified by UV curing with different wavelength bands. We have demonstrated UV hardening of ULK-SiOC (k=2.65) with two types of UV bulbs (UV-X and UV-Y) and the UV modifications of ULK-SiOC film properties are characterized by using FT-IR spectroscopy, 29Si Solid-state NMR spectroscopy and Raman spectroscopy. FT-IR and NMR analyses reveal that UV-Y curing is preferable for UV curing modification of ULK-SiOC. UV-Y curing increases Q mode peak in NMR, resulting in the enhanced Si-O crosslinking, while UV-X curing increases TH mode and TOR mode peaks. Spin lattice relaxation time T1 for 29Si is decreased with UV curing. This result indicates that UV curing enhances molecular motion in Si-O network. Raman analysis shows that UV curing increases amorphous carbon groups, which corresponds to the enhanced molecular motion in Si-O network.
Critical and Sub-critical Debonding in Nano-clustering Porous Low-k Films
Authors: Smith Ryan Scott , Uchibori C. J. , Ho P. S. , Nakamura T.
Published: April 2011

Very few porous low-k dielectric materials meet the basic requirements for integration into the back end of the line (BEOL) metallization. According to the International Technology Roadmap for Semiconductors, 2005, candidates for the 45 nm node need a k<2.2 and a minimum adhesion strength of 5 J/m2. Recently, a low-k dielectric material was developed, called nano-clustered silica (NCS). It is a spin-on glass with k<2.3. NCS is constitutively porous, with a micro- and mesopore size of ~2.8 nm. The first reported adhesion strength of this material was 10+ J/m2. We investigated the nature of the adhesive strength of NCS by critical and sub-critical fracture and Fourier Transform IR Spectroscopy (FTIR). The four-point bend technique and a mixed-mode double cantilever beam technique were employed. The sub-critical crack growth studies were performed in humid environments and ambient temperatures. Different post-treatments were used on NCS to achieve different molecular structure, as measured with FTIR. A correlation between molecular structure and critical adhesion energy was found. Atomistic parameters were calculated from the sub-critical crack growth data. A dependency of fracture behavior on post-treatment and, therefore, structure was observed.
Thermal and Dielectric Stability of Parylene X
Authors: Senkevich Jay J. , Carrow Brad , Wang Pei-I
Published: April 2011

Integrating pore sealing and barrier dielectric materials into back-end-of-the-line (BEOL) structures is challenging due to the requirements of high thermal stability, electrical stability (high breakdown, low leakage, and low dielectric constant), and barrier-like properties of the films. With Al etch-back metallization the dielectric needed to be stable to 450 °C due to Al reflow but now the thermal budget is shrinking with Cu metallization. Now the limiting factors are solder and ultra-low k (ULK) dielectric cure temperatures. These temperatures may still require thermal anneals exceeding 400 °C, which is very demanding on organic-based systems. Parylene X, a pore sealing chemical vapor depositable polymer, is deposited a room temperature via a precursor that allows the polymer to be self-initiated and without any by-products. The deposition platform allows controlled penetration of the organic polymer that allows significant fracture toughness improvement for the ULK dielectric. The polymer starts to cross-link at 175 °C with full conversion by 380 °C as measured by FT-IR spectroscopy. The polymer is shown to be stable to 420 °C with a dielectric constant of 2.7 and a leakage current of 0.5 × 10-9 A/cm2 at 0.67 MV/cm using MIMCAP structures. Parylene × was shown to have barrier-like properties in contact with both Ta and Cu metallization using bias-temperature stress (BTS) measurements at 0.5 MV/cm and 150 °C. In a Cu/Ta/parylene X/ULK dielectric stack, Ta a carbide former, can be used as an adhesive layer linking Cu to parylene × or the organic-based surface since parylene × has barrier-like properties.
PECVD Versus Spin-on to Perform Porous ULK for Advanced Interconnects: Chemical Composition, Porosity and Mechanical Behavior
Authors: Jousseaume Vincent , Le Cornec Charles , Ciaramella Frederic , Favennec Laurent , Zenasni Aziz , Simon Gurvan , Simon Jean Paul , Gerbaud Guillaume , Passemard Gerard
Published: April 2011

Porosity introduction in a-SiOCH matrix is a main research field in microelectronic. Two techniques are used to deposit these dielectric thin films: spin-on or Plasma Enhanced Chemical Vapor Deposition (PECVD). In this work, different porous a-SiOCH thin films (k close to 2.2 – 2.3) are studied. Several synthesis ways are used to deposit these a-SiOCH layers: by porogen approach, self assembling or nanoclustering techniques for spin-on, and using a porogen approach for PECVD. Impact of deposition process and curing on material crosslinking are investigated. The skeleton structure is correlated to the elastic properties whatever the deposition technique used. Finally, porosity and pore interconnectivity are studied and the results show that barrier diffusion is less pronounced in case of small pores size such as those obtained by PECVD.
Real Time Study of Cu Diffusion through a Ru Thin Film by Photoemission Electron Microscopy (PEEM)
Authors: Hess Wayne P. , Xiong Gang , Sun Y.-M. , Joly Alan G. , Beck Kenneth M. , White J. M. , Hess Wayne P.
Published: April 2011

We demonstrate the efficacy of Photoemission Electron Microscopy (PEEM) as a tool to detect metal diffusion processes at nanoscale spatial resolution in real time. For a sample comprising a nominally 1 nm physical vapor-deposited (PVD) Ru thin film covering a thick Cu substrate, we have observed the appearance of bright features on a dark background as the temperature is monotonically increased and irradiated with photons from a Hg arc lamp. These bright features are the result of a lower work function due to Cu diffusion through the Ru film.
Electromigration-Induced Plastic Deformation in Cu Damascene Interconnect Lines as Revealed by Synchrotron X-Ray Microdiffraction
Authors: Budiman Arief , Tamura N. , Valek B. C. , Gadre K. , Maiz J. , Spolenak R. , Patel J. R. , Nix W. D.
Published: April 2011

The Scanning X-Ray Submicron Diffraction (μ-SXRD) technique using focused synchrotron radiation white beam developed in the Beamline 7.3.3 at the ALS Berkeley Lab has been used to study the microstructural evolution at granular level of Cu polycrystalline lines during electromigration. Plastic deformation was observed in damascene Cu interconnect test structures during this in situ electromigration experiment and before the onset of visible microstructural damage (voiding, hillock formation). We show here that the extent of this electromigration-induced plasticity is dependent on the line width. In wide lines, plastic deformation manifests itself as grain bending and the formation of subgrain structures, while only grain rotation is observed in the narrower lines. The analysis of the Laue reflections allow for the determination of the geometrically necessary dislocation density in individual grains as well as for the misorientation angles between small angle boundaries generated by polygonization. The deformation geometry leads us to conclude that dislocations introduced by plastic flow lie predominantly in the direction of electron flow and may provide additional easy paths for the transport of point defects. Furthermore, we observe that the rotation axis of this plastic deformation coincides with one of the <112> line directions of the known slip systems for FCC crystal, and that it is always very close (within a few degrees) to the direction of the electron flow. This finding suggests a correlation of the proximity of certain <112> line directions to the direction of electron flow with the occurrence of plastic behavior. One important practical implication of this particular finding is that the grain texture of the line might thus play an important role in giving higher resistance towards early plastic response of the Cu line upon the electromigration loading.
Effect of Cu Migration in a Field Induced Dielectric Failure
Authors: Hwang Sang-Soo , Jung Sung-Yup , Joo Young-Chang
Published: April 2011

For the study of dielectric failures by Cu migration, TDDB (time dependent dielectric breakdown) and 1-D FDM simulation was carried out. We tested TDDB using a simple MIS structure with no barrier Cu electrode. From our TDDB results, the TTF's in the acceleration condition and the characteristic parameter of TDDB were obtained. In the simulation parts, 1-D FDM simulation was accomplished considering space charge effect due to Cu ions.

The objective of TDDB is to predict of TTF (time to failure) in the service condition form the results of an accelerating condition. The characteristic of TTF's follows E model in the accelerating condition, in the service condition, the deviation from E model was observed. This different characteristic of TTF can be explained by the mechanism of Cu migration enhanced by an applied E field. Our simulation and TDDB results reveal that the deviation from E model does not mean the change of failure mechanism, but it shows the characteristics of Cu migration.
Electrical Resistance Anomalies During Electromigration Testing of Cu Conductor Lines: Examples of Local Melting?
Authors: Zhang Hongqing , Wang Gan , Cargill III G. S.
Published: April 2011

We have observed abrupt, reversible resistance changes during electromigration (EM) testing of 0.16μm thick, 100μm long damascene Cu conductor lines with TaN liners and W vias. Lines of 0.2μm, 0.8μm and 2μm widths were tested and compared. The tests were conducted at temperatures of 300C – 350C and with current densities of 0.6 × 106 A/cm2 to 1.6 × 106A/cm2. In most cases an incubation period with negligible resistance increase is followed by a period of continuous, gradual resistance increase, attributed to formation and growth of voids in the conductor line. With further EM, the resistance curves show spike like features, with a sudden resistance increase, followed by a resistance decrease, often to values close to those before the start of EM. In other cases, no resistance decrease occurs, and the line fails. We present resistance data, microstructural observations and thermal calculations that suggest that the resistance decrease results from sudden, local Joule heating melting of conductor line segments and voids being partially filled by the back-flowing liquid Cu, which then solidifies. In some cases line failure results from liquid Cu erupting through the top surface passivation layer, rather than flowing back to fill voids in the line.
Design an Electroplated Frame Freestanding Specimen for Microtensile Testing of Submicron thin TaN and Cu Film
Authors: Lin Ming-Tzer , Tong Chi-Jia , Chiang Chung-Hsun
Published: April 2011

A novel design electroplating spring frame structure specimen is demonstrated here. The specimen can be fit into a specially designed microtensile apparatus which is capable of carrying out a series of tests on submicron scale freestanding thin films.

Certain thin films applicable in CMOS interconnect and low K materials were tested including sputtered Copper, Tantalum Nitride thin films. Metal specimens were fabricated by sputtering. For Tantalum Nitride film samples, Nitrogen gas was introduced into the chamber during sputtering Tantalum films on the silicon wafer.

We found the modulus of Copper and Tantalum Nitride thin films thin films with thickness of 200 to 800nm at room temperature.
Non-Destructive Measurement of Deep Embedded Defects in Silicon using Photoacoustic Microscope (PAM)
Authors: Xu Lu , Lowney Donnacha , McNally Patrick J , Fernandez Eva Gomez , Stopford Jennifer
Published: April 2011

An automatic gas cell photoacoustic microscope has been used to characterize two laser machined air trenches in a silicon substrate from the back side. Both amplitude and phase images reveal the subsurface features. The frequency dependence of the photoacoustic signals with different laser spot sizes was compared with a 1-D model. The effect of lateral heat diffusion on subsurface defect characterization was investigated and the results can be applied to other photothermal techniques.
Benefits and Trade-offs in Multi-Level Air Gap Integration
Authors: Hoofman Romano , Daamen Roel , Nguyenhoang Viet , Michelon Julien , Gosset Laurent G. , Arnal Vincent , de Pontcharra Jean , Gaillard Frederic , Caluwaerts Rudy , Bruynseraede Christophe , Beyer Gerald
Published: April 2011

In this paper, two different air gap integration approaches are discussed in detail. Firstly, air gaps can be created using sacrificial materials, which are selectively removed through a capping layer either by wet- or dry-etching or by thermal decomposition. The second class benefits from the non-conformal deposition of different CVD dielectrics, which creates air gaps for narrow spaced lines. The benefit of air gaps in terms of capacitance reduction in multilevel interconnects is well known, therefore the authors will mainly concentrate on the challenges associated with the introduction of air gaps in interconnect systems. It will be shown that interconnect containing air gaps does not suffer more from reliability challenges than interconnects with porous low-k dielectrics. Therefore, air gaps can be considered as a viable option for the 32nm node and beyond.
Studies of the Coefficient of Thermal Expansion of Low-k ILD Materials by X-Ray Reflectivity
Authors: Antonelli George Andrew , Phung Tran M. , Mortensen Clay D. , Johnson David , Goodner Michael D. , Moinpour Mansour
Published: April 2011

The electrical and mechanical properties of low-k dielectric materials have received a great deal of attention in recent years; however, measurements of thermal properties such as the coefficient of thermal expansion remain minimal. This absence of data is due in part to the limited number of experimental techniques capable of measuring this parameter. Even when data does exist, it has generally not been collected on samples of a thickness relevant to current and future integrated processes. We present a procedure for using x-ray reflectivity to measure the coefficient of thermal expansion of sub-micron dielectric thin films. In particular, we elucidate the thin film mechanics required to extract this parameter for a supported film as opposed to a free-standing film. Results of measurements for a series of plasma-enhanced chemical vapor deposited and spin-on low-k dielectric thin films will be provided and compared.
Applications of Raman Spectroscopy in Cu CMP: In-situ Detection of Chemical Species in the Slurry
Authors: Kondoju Siddartha , Lucas Pierre , Raghavan Srini , Fischer Paul , Moinpour Mansour , Oehler Andrea
Published: April 2011

Slurries used for copper CMP have a rich chemistry, which may change during the course of polishing due to consumption and decomposition of molecular species. Various aspects, such as small layer thickness (<50 μm), continuous flow of the slurry, and dynamics of the film removal process pose great challenge to the monitoring of slurry components between the pad and the wafer. The slurry constituents such as oxidants and corrosion inhibitors have unique signatures that can be detected using spectroscopic techniques. In this paper, work carried out to explore the use of Raman spectroscopy to detect and quantitate chemical species such as hydroxylamine, benzotriazole and hydrogen peroxide in-situ will be presented. More detailed study pertaining to the protonation of hydroxylamine with respect to the pH will also be presented. An abrasion cell integrated with a Raman spectrometer was used to make the measurements.
AFM Measurements of Adhesion between CMP Slurry Particles and Copper
Authors: Burtovyy Ruslan , Liu Yong , Zdyrko Bogdan , Tregub Alex , Moinpour Mansour , Buehler Mark , Luzinov Igor
Published: April 2011

Adhesion between abrasive particles and surfaces being polished plays an important role in chemical mechanical planarization (CMP) processes. The changes in particle - surface and particle – particle interactions can significantly influence the effectiveness of material removal and cleaning methods. To determine the adhesion between actual abrasive particles and different surfaces treated by the CMP process a method employing atomic force microscopy (AFM) technique is being developed.

The monolayer of silica abrasive nanoparticles was deposited on silicon wafer covered with polymer anchoring layer. High affinity of the thin polymer film to the particles and wafer ensures the stability of particles monolayer on the surface during measurements. AFM cantilever was modified with attachment of 20-40 microns hollow glass bead (representing a flat surface), which then was covered with copper using physical vapor deposition technique. Force-distance curves were collected employing AFM force volume mode and used to calculate the adhesion value. The effect of different factors (such as pH, presence of surfactants) on adhesion between copper surface and silica slurry has been studied.
Anomalous pH Actuation of a Chitosan/SWNT Microfiber Hydrogel with Improved Mechanical Property
Authors: Shin Su Ryon , Park Sang Jun , Yoon Seong Gil , Lee Chang Kee , Shin Kwang Min , Gu Bon Kang , Shin Min Kyoon , Kim Min Sup , Kim Yu Jin , Kim Seon Jeong
Published: April 2011

Composite fibers composed of chitosan and single-wall carbon nanotubes (CNTs) have been fabricated using a wet spinning method. The dispersion was improved by the sonic agitation of the CNTs in a chitosan solution followed by centrifugation to remove tube aggregates and any residual catalyst. The mechanical behavior was investigated using a dynamic mechanical analyzer (DMA). The mechanical tests showed a dramatic increase in Young's modulus for the chitosan/CNT composite fibers fabricated using the improved dispersion method. The strain on the microfibers was determined from tensile load measurements during pH switching in acidic or basic electrolyte solutions. The microfibers showed a general actuation behavior of expanding at pH = 2 and contracting at pH = 7 under low tensile loads. However, a reverse of this actuation behavior was exhibited under high tensile loads. This anomalous pH actuation is both new and surprising. It was explained from an analysis of the differences in sample stiffness and Poisson’s ratio under tensile load in electrolyte solutions with different pH values.
Pore Size Dependence of Proteinase K Diffusion Through Sol-Gel Derived Silica
Authors: Dong Winny , Lin Weijen , Contreras Nicole , Elmatari Doja , Lin YiHsuan , Torres Maria
Published: April 2011

Sol-gel derived silica particles are candidates for vehicles for injectable controlled drug-delivery. In this study, Proteinase K was the model biomolecule encapsulated in the silica xerogel, ambigel, and aerogel particles. The surface area and average pore diameter of these particles are reported. Both the amount of Proteinase K released from the particles and the activity of the released Proteinase K were measured as a function of time. The primary finding of this study is the effect of pore diameter on the specific activity of Proteinase K released from these particles.
Embedded Piezoresistive Microcantilever Sensors: Materials for Sensing Hydrogen Cyanide Gas
Authors: Porter Timothy , Vail Tim , Eastman Michael , Stewart Ray , Reed Jim , Delinger William
Published: April 2011

We have used embedded piezoresistive microcantilever (EPM) sensors in the detection of hydrogen cyanide gas. EPM sensors are small, MEMS-based devices consisting of a tiny piezoresistive microcantilever partially embedded into a “sensing material” designed to respond volumetrically when exposed to the desired analyte. These EPM sensors may be very small, operate on simple and inexpensive support electronics, are highly resistant to movement or shock, may be operated by hardwire connection or wirelessly in large numbers, and are capable of detecting many different analytes. In this study, we have used EPM sensors to detect hydrogen cyanide gas. Preliminary results indicate that the EPM sensors provide a fast response (less than 5 seconds) to levels of HCN that may be lethal to humans.
Aromatic Hydrocarbon Detection Using Self-Assembled Monolayer Coated Cantilevers
Authors: Riley Andrew E , Schilowitz Alan M , Yablon Dalia G , Disko Mark M
Published: April 2011

The presence of toluene and xylene is sensed via surface stress induced deflection of microcantilevers functionalized with self-assembled monolayers (SAMs). Monolayers are formed on gold coated cantilevers using alkanethiols, mercaptanols, and aromatic thiols. These coatings create a variety of chemical functionalities at the cantilever surface, which impact the interactions between target molecules and the cantilever. The differential responses of the cantilevers are investigated as a means to selectively detect aromatic vapors at parts per thousands (ppth) levels.
Tin Dioxide Nanodimensional Film Based H2 sensor
Authors: Dmitriev Serghei
Published: April 2011

Paper presents results of investigation aimed at the development of tin dioxide nanodimensional film gas sensors (NDFGS) with high sensitivity to hydrogen. Specifics of the performed research consist in the approach based on the combination of utilization nanodimensional metal oxide film, as gas sensitive element of device, and group electron technology methods that allows to arranging from small to large scale manufacturing of given NDFGS.

Gas sensitive nanodimensional film (NDF) had been formatted by means of chemical spray pyrolysis method on the both ceramic substrate for study and optimization of electrophysical and gas sensitive characteristics and “chip” of gas sensor (GS) preliminarily produced through group electron technology. Films were deposited at the temperatures in interval 400-500°C from water solutions of SnCl4.5H2O precursor. The thickness of SnO2 films was varied in the range 40-80 nm.

Study of electrophysical characteristics of obtained layers has shown that the last one possess resistance on the level 105-106 Ohm/ at the working temperatures of GS. Gas sensitivity was determined as ratio of SnO2 film resistance in the pure air and in the presence of gas impurity in atmosphere (S=Rgas/Rair). Values of R were determined through Van-der-Pauw method.

X-ray and SEM investigation has allowed establishing the interconnection between technologic parameters, nanostructure and gas sensitive characteristics of obtained films.

Gas sensitivity S of the deposited undoped films has amounted 9-10 relative units to the 100 ppm of hydrogen in air. Modification of gas sensitive properties of tin dioxide NDF through bulk and surface doping with Pd has allowed to increasing hydrogen sensitivity up to almost 104 rel. units, providing the detection of hydrogen at the concentration on the level 1 ppm and shift of the sensitivity maximum from 350°C (in the case of undoped films) to 150°C (Pd doped NDF).

Performed sensor chip thermal regimes modeling has allowed developing of the NDFGS topology with reduced power consumption (< 30 mW).
Inverse Opal Nanoassemblies: Novel Architectures for Gas Sensors The SnO2:Zn Case
Authors: Sutti Alessandra , Calestani Gianluca , Dionigi Chiara , Baratto Camilla , Ferroni Matteo , Faglia Guido , Sberveglieri Giorgio
Published: April 2011

A novel technique is here presented, based on inverse opal metal oxide structures for the production of high quality macro and meso-porous structures for gas sensing. Taking advantage of a sol-gel templated approach, different mixed semiconducting oxides with high surface area, commonly used in chemical sensing application, were synthesized. In this work we report the comparison between SnO2 and SnO2:Zn. As witnessed by Scanning and Transmission Electron Microscopy (SEM and TEM) analyses and by Powder x-ray Diffraction (PXRD), highly ordered meso-porous structures were formed with oxide crystalline size never exceeding 20 nm. The filled templates, in form of thick films, were bound to allumina substrate with Pt interdigitated contacts and Pt heater, through in situ calcination,in order to perform standard electrical characterization. Pollutant gases like CO and NO2 and methanol, as interfering gas, were used for the targeted electrical gas tests. All samples showed low detection limits towards both reducing and oxidizing species in low temperature measurements. Moreover, the addiction of high molar percentages of Zn(II) affected the behaviour of electrical response improving the selectivity of the proposed system.
Chain Morphologies in Blue-Emitting Polyfluorenes: Impact on Light-Emitting Diodes
Authors: Guha Suchi , Arif M. , Volz C.
Published: April 2011

Dioctyl-substituted polyfluorene (PF) is especially well known for the presence of an unusual spectral feature identified as the beta phase, known to originate in regions of enhanced chain planarity. Although this phase appears as a minority constituent it dominates the emission, resulting in a red shift of the luminescence. We present Raman scattering studies of poly[9,9'-(di n, octyl) fluorene] as a function of thermal cycling that establish a connection between the conformational isomers and chain morphology. Density-functional theory calculations of the vibrational spectra of single chain oligomers in conjunction with our experimental results demonstrate the incompatibility of the beta phase with the overall alpha crystalline phase. Further, electroluminescence and photoluminescence measurements from PF-based light-emitting diodes are presented and discussed in terms of the crystalline phases and chain morphologies in the PFs.
Pb2+ and Ce3+ Doped SrZnO2: New Blue Luminescent Phosphors
Authors: Manavbasi Alp , LaCombe Jeffrey C
Published: April 2011

Two new blue emitting phosphors, SrZnO2:Pb2+ and Ce3+ were synthesized by adipic acid and sucrose templated sol-gel routes, respectively. The resulting phosphor particles were fine, nanocrystalline and pure. The optimum activator concentrations were found to be 1 mol% Pb2+ and 12 mol% Ce3+. Two excitation bands centered at 283 and 317 nm, plus a weak shoulder at 275 nm were observed for Pb2+ doped samples, however only one broad excitation band with a maximum at 294 nm was observed for Ce3+ doped samples fired at 1000 °C for 2h. The emission spectra of SrZnO2:Pb2+ showed a very broad band extending from 374 to 615 nm with a maximum at ~455 nm which was ascribed to the 3P1 ¡æ 1S0 transition on the Pb2+ ions allowed by the strong spin-orbit (SO) coupling. Similarly, SrZnO2:Ce3+ showed a broad emission band extending from 374 to 609 nm and centered at 467 nm. This broad emission was attributed to the 5d1 ¡æ 4f1 transition of Ce3+ ions. The lower level 2F5/2 of the 4f1 is populated but the level 2F7/2 is almost empty at room temperature where all measurements were taken. The luminescence properties of Ce3+, K+ co-doped SrZnO2 revealed that the characteristic band locations remained the same and the ratio of emission to excitation intensities were constant. X-ray diffraction patterns showed that the SrZnO2 phase started to form at 900 °C (after 2 hrs), and the single-phase SrZnO2 obtained at 1000 °C. SEM micrographs of both phosphors have a rounded and filled morphology for individual particles with an approximate diameter of 50-250 nm. Dynamic light scattering studies revealed that average particle size is around 1 ¥ìm for both phosphors.
UV and VUV Spectroscopy of ns2-type Ions Co-doped YBO3:Eu3+ Red Phosphor
Authors: Wang L.L. , Wang Y.H. , Hua W.X.
Published: April 2011

YBO3:5% Eu3+ co-doped with some ns2-type ions were synthesized by solid-state reaction and their luminescence properties under ultraviolet (UV) and vacuum ultraviolet (VUV) region were investigated. The results indicated that in the excitation spectrum of YBO3:5%Eu3+, the strong charge transfer (CT) band of Eu3+ was located in the UV region and the absorption band of the host lattice lay in the VUV region. When the ns2-type ions, such as Sn2+ and Sb3+(n=5), Tl+, Pb2+ and Bi3+(n=6) were co-doped into the host lattice of YBO3:5%Eu3+, the CTS band of Eu3+ was shifted. The intensity of the host lattice absorption band was improved with the incorporation of Tl+, Pb2+ or Bi3+, while decreased with Sn2+ or Sb3+. These luminescent phenomena were analyzed in detail and possible reasons were given.
Optical Properties of Alkali Doped Group IV Nano Materials
Authors: Gokturk Hal
Published: April 2011

Optical properties of sodium and other alkali metals (lithium & potassium) incorporated into nano hosts of group 4 elements (carbon, silicon & germanium) were investigated as candidates for solid state light emitting materials. First, optical properties were calculated by quantum mechanical simulations using TDDFT method. Results of the simulations indicate that alkali doped group 4 nano hosts exhibit optical transitions in and around the visible range whereas, undoped nano hosts do not have any at similar wavelengths. Some combinations of alkali dopant and nano host give rise to multiple transitions in the visible. One of the simulated combinations, Li dopant and carbon nano host was chosen to be synthesized for experimental verification. Optical absorption and emission characteristics of the synthesized material were measured and compared with those obtained from quantum mechanical calculations. Both the wavelength and the relative intensity of the measured optical transitions were found to be in good agreement with the results of the calculations. Alkali metals which have good light emission characteristics can be combined with group 4 indirect semiconductors to obtain new nano materials which have interesting optical properties in the visible.