bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Detailed Study of Void Motion In Passivated Aluminum Interconnects
Authors: Doan Jonathan C. , Bravman John C. , Flinn Paul A. , Marieb Thomas N. 
Published: April 2011

AbstractVoid motion can be an important part of electromigration failure in interconnects. Investigating this process is difficult due to the large variation in behavior in identical samples tested under identical conditions. To deal with the large variability, we have tested 50 samples to failure at four different accelerated test conditions. Because our automated, in-situ technique images an entire test structure, the complete history of a test line is recorded. By testing many samples under direct observation, the complex motion of electromigration voids was comprehensively studied.
Cause of the Decrease in Electromigration Resistance in Am/Al3Ti Lines
Authors: Kameyama A. , Masuzaki K. , Okabayashi H. , Sakata T. , Mori H. 
Published: April 2011

AbstractTo investigate the cause of the lower electromigration (EM) resistance in Al/Al3Ti lines compared to that in Al/TiN lines, we studied the Al microstructure and the EM characteristics. Even after fine-grained Al3Ti formation through a reaction of the Al and Ti, the Al microstructure of the unreacted Al on the AI3Ti remained a bamboo grain structure with a high 111 orientation. Thus, the Al grain structure and texture did not affect the EM resistance. The critical current density for voiding was 0.64 MA/cm2. The Al drift velocity in the Al/Al3Ti bamboo lines was two orders of magnitude higher than that for Al/TiN bamboo lines from 180°C to 280°C. This higher Al drift velocity decreased the EM resistance in the lines. The activation energy of Al drift in the AI/AI3Ti lines was 0.6 to 0.7 eV, which is lower than that for Al lattice diffusion. Thus, the Al lattice is not the dominant transport path in Al/Al3Ti lines. The dependence of the Al drift velocity on the line size showed that the Al/Al3Ti interface was the dominant path in the Al/Al3Ti bamboo lines. Thus, we concluded that the rapid Al transport through the Al/Al3Ti interface decreases EM resistance in Al/Al3Ti lines.
Evaluation of Current Ramp Test for In-Line Electromigration Test
Authors: Low Kia Seng , Glasow Alex v. , Poetzlberger Hans 
Published: April 2011

AbstractCurrent ramp tests are performed in a number of experiments to check their validity as an in-line monitoring tool for electromigration evaluation. We discuss our various findings from a series of experiments conducted to validate the usefulness of the current ramp test, using the standard NIST test structure. First, we check whether the current ramp test, using breakdown energy of metal (BEM test), shows the effect of a Ti/TiN underlayer on the reliability of A1–0.5wt%Cu unpassivated interconnects. The second experiment compares current ramp testing with fuse testing. Next we check if current ramp testing gives any indication of interconnect quality following different stages of our sputtering process, and in particular different degas temperatures. The last experiment tries to correlate the breakdown energy obtained from current ramp testing with the lifetime obtained from conventional long term electromigration testing of different combinations of line stack and line stack dimensions. From the results of the experiments, we conclude that current ramp testing using the breakdown energy of metals cannot be used quantitatively for electromigration evaluation using conventional NIST test structures.
X-Ray Microbeam Studies of Electromigration
Authors: Cargill III G. S. , Ho A. C. , Hwang K. J. , Kao H. K. , Wang P.-C. , Hu C.-K. 
Published: April 2011

AbstractThe interplay between stress and electromigration has been recognized since I. A. Blech et al. used x-ray topography in 1976 to demonstrate that stress gradients developed during electromigration. Availability of high brightness synchrotron x-ray sources, high stability energy dispersive detectors, high resolution area detectors, and pinholes, capillaries and other optical elements for forming x-ray microbeams, has made possible more quantitative, real time measurements of strains and composition changes which develop in polycrystalline metal conductor lines during electromigration. This paper describes advances made in this area, implications of results which have been obtained, and prospects for further progress.
In-Situ X-Ray Microbeam Cu Fluorescence and Strain Measurements on Al(0.5 AT.% Cu) Conductor Lines During Electromigration
Authors: Kao H.-K. , III G. S. Cargill , Hwang K. J. , Ho A. C. , Wang P.-C. , Hu C.-K. 
Published: April 2011

AbstractWe have used x-ray microbeam fluorescence and diffraction for in-situ measurements of Cu concentration and strain during 36 hours of electromigration with current density 5×105 A/cm2 at temperature 310°C for a passivated 10μm-wide, 200μm-long Al(0.5 at.% Cu) conductor line. These measurements indicate that Cu is quickly depleted at the cathode end of the line and is piled up at the anode end, where the Cu concentration first increases, then decreases, and finally remains constant. A void begins growing at the cathode end of the line about two hours after the start of current flow, with a nearly constant void growth rate of 1 μm/hr for the remainder of the test. The evolution of stresses within the line during electromigration involves changes by 100's of MPa and is more complex than seen previously for electromigration under similar conditions for pure Al conductor lines.
X-Ray Microbeam Measurement of Local Texture and Strain in Metals
Authors: Chung Jin-Seok , Tamura N. , Ice G. E. , Larson B. C. , Budai J. D. 
Published: April 2011

AbstractSynchrotron x-ray sources provide high-brilliance beams that can be focused to submicron sizes with Fresnel zone-plate and x-ray mirror optics. With these intense, tunable or broadbandpass x-ray microbeams, it is now possible to study texture and strain distributions in surfaces, and in buried or encapsulated thin films. The full strain tensor and local texture can be determined by measuring the unit cell parameters of strained material. With monochromatic or tunable radiation, at least three independent reflections are needed to determine the orientation and unit cell parameters of an unknown crystal. With broadbandpass or white radiation, at least four reflections and one measured energy are required to determine the orientation and the unit cell parameters of an unknown crystal. Routine measurement of local texture and strain is made possible by automatic indexing of the Laue reflections combined with precision calibration of the monochromator-focusing mirrors-CCD detector system. Methods used in implementing these techniques on the MHATT-CAT beam line at the Advanced Photon Source will be discussed.
Effect of a Titanium Interlayer on the Performance of the Titanium Nitride Diffusion Barrier
Authors: Lu K. Y , Chen J. S. 
Published: April 2011

AbstractWe have studied the effect of a Ti interlayer on the behavior of a TiN diffusion barrier for Al and Cu metallizations. Thermal stability of Al/Ti/TiN/<Si> and Al/TiN/<Si> samples annealed at 400–600°C for 30 min was investigated using Auger electron spectroscopy (AES), glancing angle X-ray diffraction and scanning electron microscopy (SEM). Sheet resistance was measured for electrical characterization.After annealing at 400°C and 500°C, the AI/TiN/<Si> samples exhibited the same sheet resistance as the as-deposited one, while the sheet resistances of the Al/Ti/TiN/<Si> samples increased upon annealing. After annealing at 600°C, pyramidal pits developed on the surface of the Al/TiN/<Si> sample, but not on the Al/Ti/TiN/<Si> sample. Sheet resistance measurements for the 600°C-annealed Al/TiN/<Si> sample resulted in a more scattered distribution and a higher average value than for the Al/Ti/TiN/<Si> sample. The results clearly indicate that the performance of the TiN barrier layer is significantly improved by including a thin Ti film between the TiN and the Al. The Ti interlayer also improves the TiN barrier performance for the Cu metallization system.
Macroscopic Modeling of Fine Line Adhesion Tests
Authors: Volinsky A. A. , Nelson J. C. , Gerberich W. W. 
Published: April 2011

AbstractMicrowedge Indentation (MWIT) and Precracked Line Scratch (PLST) tests have been developed for adhesion measurements of microscale fine lines. In the MWIT a symmetric wedge-shaped probe is driven downward into a thin film line debonding it from the substrate. For the PLST, a precrack is introduced at one end of a thin metal line on a substrate. The line is loaded from the precrack end by an asymmetric diamond wedge until the crack propagates. When the crack reaches its critical length at a certain critical load, the film buckles.The mechanics of these tests are based on several assumptions of thin line behavior, which are not experimentally observable due to small line sizes and equipment limitations. Testing similar but larger lines allows for the direct observation of line delamination and buckling, which can be used for calculating in-situ crack lengths as well as instantaneous strain energy release rates.Both MWIT and PLST models [1–4] were experimentally verified on the macroscopic scale using polycarbonate as a line material bonded to a steel substrate with cyanoacrylate. New features such as initial crack growth as well as instantaneous crack growth at buckling were observed. Modified Kic tests were performed for strain energy release rate comparison. Adhesion values ranging from 200 to 1000 J/m2 were measured for this system, and had very strong mode mixity dependence. Connectivity to the microscale is through previous experiments by de Boer, et al using fine line W/SiO2/Si systems [ 1–4].
TiB2as a Diffusion Barrier for Cu/<si> Metallization
Authors: Wang J. L. , Chen J. S. 
Published: April 2011

AbstractTiB2, films deposited by co-sputtering from a boron and a TiB, target are evaluated as the diffusion barrier for Cu metallization. Material characteristics of the TiB, films and metallurgical interactions of the Cu/TiB2/<Si> system annealed at 400−700°C for 30 min, in a 80%Ar+20%H2 flow, were investigated by glancing angle X-ray diffraction, Auger electron spectroscopy (AES), and scanning electron microscopy (SEM). Sheet resistance was measured for electrical characterization.The composition and resistivity of the sputtered TiB1 films varied with the bias applied on the substrate. To obtain a low film resistivity, a negative bias of 200V was applied during sputtering. The resulting TiB2 film is nanocrystalline with a resistivity of 300 μΩcm. After copper deposition, the Cu/TiB2/<Si> samples have a constant sheet resistance after annealing up to 600°C for 30min. The overall sheet resistance of the sample increases by five orders of magnitude after annealing at 700°C, and scanning electron micrographs reveal that the sample surface is severely deteriorated after annealing at 700°C.
Immortal InterConnects—Prevent Cracking and Limit Void Size
Authors: Suo Z. , Ma Q. , Meyer W. K. 
Published: April 2011

AbstractThis paper considers an aluminum line in a multilevel interconnect structure. Upon cooling from the processing temperature, differential thermal contraction causes a triaxial tensile stress state in the aluminum line; voids may initiate and grow to relax the stress. When a direct voltage is applied, the electric current causes aluminum atoms to diffuse. The interconnect will evolve to a state with a high pressure at the anode, and a large void at the cathode. The pressure may crack the surrounding insulator or debond an interface, extruding aluminum. The void may uncover the via contact area, substantially increasing electrical resistance. Provided neither failure mode occurs, aluminum electromigration will stop and the interconnect will function forever. This paper examines the conditions under which the interconnect is immortal.
Interconnect Reliability Study Using a Microscopic Nucleation Model for Electromigration
Authors: Tammaro M. , Setlik B. 
Published: April 2011

AbstractA microscopic nucleation model for electromigration is proposed. The solution to the master equations for site occupancy produces a variable current exponent with 1 < n < 2. These results disprove previous claims that n = 2 in nucleation models. We also address the long-standing speculation regarding an additional temperature dependence in Black's equation. Under the premise that the activation energy in Black's equation, Ea, should be equal to the energy barrier for atomic hopping, we provide evidence for an additional T2 dependence of the failure time. Microscopic modeling provides an explicit connection between the macroscopic model behavior and the microscopic parameters of the model. A continuum treatment of our model is derived and compared with standard continuum treatments.
Electromigration Voiding in Argon-Implanted Interconnects
Authors: Meier N. E. , Doan J. C. , Marieb T. N. , Flinn P. A. , Bravman J. C. 
Published: April 2011

AbstractElectromigration is a complex process consisting of the nucleation, growth, and movement of voids. While interconnect microstructure plays a major role in determining void nucleation time and location of void nucleation, recent studies have shown that this is not the only contributing factor. Thermodynamics and kinetics-based calculations by Flinn and Gleixner et al. have shown that electromigration void nucleation by vacancy condensation at both homogeneous and heterogeneous sites will not occur at a reasonable rate without a mechanism for reducing or altogether eliminating the energy barrier for nucleation. By implanting argon ions into the aluminum interconnect lines, we introduce an initial defect population (argon bubbles) of controlled size and location.Tests were performed in a high-voltage SEM (120 keV), which enables in-situ observation of the voiding process through the passivation layer. Images taken throughout the in-situ tests were analyzed to determine void nucleation times and locations. In the argon-implanted interconnects, ten of the 15 voids that nucleated were within implanted regions. Voids nucleated in the interior of the line within the implanted regions, as well as at the passivation/sidewall interface where voids are typically seen in conventional electromigration tests. In addition, voids in implanted regions nucleated much more quickly than those in unimplanted regions. These observations support the idea of argon bubbles reducing the nucleation barrier. TEM was used to analyze the microstructure of both control and implanted interconnect lines.
A Beem Study of PtSi Schottky Contacts on Ion-Milled Si
Authors: Ru Guo-Ping , Detavernier C. , Donaton R. A. , Blondeel A. , Clauws P. , Meirhaeghe R. L. Van , Cardon F. , Maex K. , Qu Xin-Ping , Zhu Shi-Yang , Li Bing-Zong 
Published: April 2011

AbstractBallistic electron emission microscopy (BEEM) and deep level transient spectroscopy (DLTS) have been used to study the effects of substrate damage introduced by an ion-milling process in PtSi/n-Si Schottky contacts. Argon ions with well-defined energies of 300, 500, 700, 1000, 1500 eV were used to sputter n-type Si substrates in an ion beam sputtering system before metal deposition and silicide formation. Histograms of the PtSi/n-Si Schottky barrier height (SBH) measured by BEEM show that the mean SBH decreases with increasing ion energy, which can be explained as a result of donor-like defects that are introduced by the ion milling treatment. From DLTS measurements, we found direct evidence for the presence of such defects.
Growth Kinetics Of SiO2 On (001)Si Catalyzed By Cu3Si At Elevated Temperatures
Authors: Huang H. Y. , Chen L. J. 
Published: April 2011

AbstractThe oxidation of Si catalyzed by 170-nm-thick Cu3Si at elevated temperatures has been investigated by transmission electron microscopy and Auger electron spectroscopy. For wet oxidation at 140–180 °C, the growth rate of the oxide layer was increased with the temperature. On the other hand, as the temperature was increased above 200 °C, the growth rate slowed down. The growth kinetics of oxide was investigated. Controlling mechanisms for the growth of oxide owing to the grain growth of Cu3Si are discussed. The activation energy for the linear growth of oxide was measured to be 0. 19 ± 0.1 eV.
Effects of Ion Metal Plasma (IMP) Titanium Deposition on Ti Silicide Formation
Authors: Sabbadini A. , Cazzaniga F. , Brambilla M. , Bresolin C. , Cusi V. , Marangon T. , Queirolo G. 
Published: April 2011

AbstractTitanium disilicide obtained by direct interaction between Si and a deposited Ti layer is a choice for low- resistance gate interconnections and source and drain areas. The properties of the TiSi2 film can be influenced by many factors; such as substrate nature and doping, the depositing Ti layer, structure dimensions [1][2][3][4]. This work is addressed to study the properties of TiSi2 film as obtained from titanium deposited by Ion Metal Plasma (IMP), which has recently been introduced in high aspect ratio contact and via applications.Its suitability for titanium silicide formation is investigated here in comparison to standard PVD deposition. The study was carried out on flat and patterned samples. Titanium silicide formed on mono- Si substrates were characterized as a function of RTP temperature in terms of sheet resistance, tilm morphology, crystallography and phase evolution. It was found that the TiSi2 film obtained from IMP- Ti is very similar to the one obtained from PVD standard deposition. However, for annealing below 700°C, an increase in the sheet resistance of the TiSi2 C49 phase from IMP- Ti compared to the one from PVD- Ti was found, and is explained by different silicide grain size. Analyses performed on patterned samples with doped silicon and poly- Si lines show similar electrical results for TiSi2 from IMP and PVD deposition; however, fbr p+ poly-Si lines, the IMP samples displayed correct TiSi2 formation down to 0.18µm line width, while the PVD wafers showed discontinuous results at these minimum feature sizes.
Agglomeration Of Cu Electroplating Seed Layers On Ultra-Thin Ta, Ta1-xNx, Tal-xOx, Contaminated Ta, and Composite Ta/Ta1-xNx Diffusion Barriers
Authors: Hartman J. W. , Yeh Helen , Atwater H. A. , Hashim Imran 
Published: April 2011

AbstractThe agglomeration of thin (10 nm) Cu films suitable for use as electroplating seed layers has been investigated on ultrathin (<4 nm) Ta, Ta1-xNx, Tal-xOx, and composite Ta/Ta1-xNx, diffusion barriers. Copper films on clean 3.6nm Ta barriers deposited by ultrahigh vacuum sputter deposition at up to 120°C are stable against agglomeration during 30 minute anneals at 360°C and display strong (022) crystallographic texture. Similar Cu films deposited on thinner Ta, Ta0 85N0 15, Ta0.95O0 05, and residual gas contaminated (∼ 1 Langmuir) Ta barriers agglomerate during annealing, and Cu films on Ta0 85N0 15 and contaminated Ta have random biaxial crystallographic texture. The density of agglomerated regions in Cu films on SiO2 and Ta0 85N0 15 is characterized as a function of thickness of an ultrathin Ta adhesion layer.
The Effect Of Surface Oxides On Cu/Ta Interfacial Interactions
Authors: Chen L. , Ekstrom B. , Kelber J. 
Published: April 2011

AbstractWe report results of Auger electron spectroscopy (AES) and temperature programmed desorption (TPD) studies under ultra high vacuum (UHV) conditions which demonstrate that even submonolayer coverages of oxygen on Ta significantly degrade the strength of Cu/Ta chemical interactions, and affect the kinetics of Cu diffusion into bulk Ta. On clean Ta, monolayer coverages of Cu will de-wet only above 600 K. A partial monolayer of adsorbed oxygen (3L O2 at 300 K) results in a reduction of the de-wetting temperature to 500 K, while saturation oxygen coverage (10 L O2, 300 K) results in de-wetting at 400 K. Diffusion of Cu into the Ta substrate at 1100 K occurs only after a 300-second induction period at this temperature. The induction period increases to 600 sec for partially oxidized Ta and to 1200 sec for saturation oxygen coverage. TPD studies indicate no desorption of Cu for temperatures below 1300 K. The higher desorption temperature of Cu (compared to the 1150 K sublimation temperature) indicates that all the Cu originally deposited is now chemically bound to Ta.
Prevention of Corner Voiding in Selective CVD Deposition of Titanium Silicide on SOI Device
Authors: Maa Jer-shen , Ulrich Bruce , Stecker Lisa , Stecker Greg , Hsu Sheng Teng 
Published: April 2011

AbstractIn the application of selective CVD of titanium silicide to SOI devices, voids were observed at the bottom corner of the spacers, which caused reduction of drain current and in extreme cases formed an open circuit. Test structures were constructed to monitor void formation. It was found the voiding became serious when the thickness of the Si film was reduced. Adjusting the deposition condition by reducing the TiCi4 flow rate or by using a two-step deposition process was able to significantly reduce the chance of void formation. On very thin Si films, voiding can be prevented by depositing a selective Si layer prior to silicide deposition.
Diffusion Barriers for Copper Metallization: Predicting Phase Stability and Reactivity using Equilibrium Thermodynamics
Authors: Ramberg C. E. , Blanquet E. , Pons M. , Ghetta V. , Bernard C. , Madar R. 
Published: April 2011

AbstractThe guidelines for designing a conductive, amorphous material, capable of thermodynamic equilibrium with copper, are defined using readily available thermodynamic information. The tradeoff between desired properties – equilibrium at the interfaces, amorphous microstructure, and electronic conductivity – are described, along with trends in relevant binary systems that result in these properties. These guidelines defined systems for experimental study, for which preliminary results are presented.
Characterization of PECVD Wnx for Copper Barrier Application
Authors: Vijayendran A. , Danek M. 
Published: April 2011

AbstractWe evaluated PECVD WNx as a potential copper barrier. Ultrathin (100 Å) PECVD WNx films were deposited utilizing WF6/N2/H2 chemistry. Films with N/W stoichiometries ranging from 0.1 to 1.0 and resistivities between 200 – 1000 μΩ-cm were deposited by varying pressure, deposition temperature, N2 flow, and H2 flow. The thermal stability of the films was evaluated by annealing Si/WNx /Cu stacks for 1 hour at temperatures up to 700°C. Barrier failure was detected by sheet resistance change and surface SIMS. The thermal stability was correlated with N/W ratio and free fluorine content as determined by temperature programmed desorption mass spectroscopy. The tests showed that films with N/W ratios between 0.3 and 0.4 had optimal barrier properties, while fluorine was seen to have a detrimental effect on barrier stability. Moreover, tests showed that the substrate affects fluorine concentration as WNx deposited on silicon dioxide has a higher interfacial fluorine content than WNx on silicon. Thus, fluorine contamination at the WNx /Si02 interface led to poor electrical reliability as measured by leakage current vs. time on MOS capacitors.