bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanical Properties and Fracture Behavior of the Cu and Cu6Sn5–Dispersed Sn-Pb Solder Bumps Processed by Screen Printing
Authors: Cha Ho-Seob , Lee Kwang-Eung , Choi Jin-Won , Oh Tae-Sung 
Published: April 2011

ABSTRACTThe mechanical properties of the 1-9 vol % Cu and Cu6Sn5-dispersed 63Sn-37Pb solder alloys were characterized with tensile test. Also, the Cu and Cu6Sn5-dispersed 63Sn-37Pb solder bumps of 760 μm size were fabricated on the Au(5 μm)/Ni(5 μm)/Cu(27 μm) BGA substrates by screen printing process, and their shear strength were characterized with variations of the dwell time at the reflow peak temperature(220°C) and aging time at 150°C. The yield strength and ultimate tensile strength of the 63Sn-37Pb solder alloy increased with dispersion of 1-9 vol % Cu and Cu6Sn5. In general, however, the Cu and Cu6Sn5-dispersed solder bumps exhibited lower shear strengths than those of the 63Sn-37Pb solder bumps The failure surface of the solder bumps after ball shear test could be divided into two regions of slow crack propagation and critical crack propagation, and the shear strength of solder bumps was inversely proportional to the slow crack propagation length.
New Stepped Process and Materials for Chip Bonding Technology on Non-rigid and Flexible Substrates
Authors: Park Sung Kyu , Han Jeong In , Kim Won Keun , Kwak Min Gi 
Published: April 2011

ABSTRACTA reliable interconnection of electrodes to the flexible polymer substrate with anisotropic conductive film (ACF) of which the conductive particles were similar in elasticity to the substrates was accomplished. The contact resistance value was maintained even while the junction was stressed under sudden changes in temperature and pressure. We found that the conduction failure is caused by the action of a complex mechanism on the changes of a joint structure. The major driving factor seems likely to be defects in the transparent electrodes due to the thermal strain of the substrate and penetration of conductive particles into the substrate. The materials of substrate and conductive particle are polycarbonate (PC) with a gas barrier layer and poly-divinylbenzene (DVB) whose hardness is similar to that of the polymer substrate, respectively. In this paper, several experiments were performed with an emphasis on the properties of polymer substrates. Furthermore, the electrical and mechanical performance of the joint structure was studied by evaluating contact resistance and scanning electron microscope (SEM) observations. Moreover, for the experiments, we fabricated test IC with Au bumps through photolithography and electro-plating process. Conductive particle with elasticity similar to that of the polymer substrates did little damage to the transparent electrodes on the substrates, and low temperature and pressure under a stepped process did not bring about their deformation either. Consequently, we adopted the results on the fabrication of plastic based flat panel display module and thus could obtain a highly reliable interconnect with a low contact resistance ( 20-25ω ).
Implementation of a low temperature wafer bonding process for acceleration sensors
Authors: Wiemer Maik , Otto Thomas , Gessner Thomas , Hiller Karla , Kapser Konrad , Seidel Helmut , Bagdahn Joerg , Petzold Matthias 
Published: April 2011

ABSTRACTThe paper describes a low temperature bond process based on an oxygen plasma pretreatment followed by 200°C and 400°C annealing which was to be integrated in our technological process flow to produce micromechanical devices in bulk and surface micromachining like acceleration sensors, gyroscopes and mirror arrays [1]. The results of infrared transmission and the measured bond strengths of the prepared test wafers will be presented in dependence on various pre-treatments and annealing times as well as temperatures. First die separation tests as well as additional detailed investigations showed that the bonding process has the potential to replace an anodic bonding process. During the development of the low temperature bond process it was shown that it is possible to reach a bond strength between 1.5 J/m2 and 2.8 J/m2 depending on the annealing conditions. To optimize the necessary size of the bond frame and to quantify the bond strength limits of the process a test pattern was designed with different arrangements of sensor structures like bond frames, spaces and chevron notch structures. The investigation showed the achieved bond yield in dependence on different sensor structures and bond conditions.
Nano-lamellar Structures in a Rolled Cu-Ag Alloy
Authors: Lyttle Mark T. , Hughes D.A. 
Published: April 2011

ABSTRACTThe microstructural evolution and texture development in a Cu-Ag eutectic during rolling are systematically investigated. A directionally solidified Cu-Ag alloy with a single dominant texture is deformed to several rolling reductions. At each of these strains, the microstructure and texture are characterized. Rapid divergence of local crystal orientations leads to the early development of high-angle Cu-Ag boundary/interface orientations, while less misorientation accumulation occurs within the individual copper and silver layers. With increasing deformation, orientations of the copper and silver phases in a single region are observed to diverge to two distinct textures, and within each of the single phases, there is a greater spread of orientations of individual cells while still retaining an identifiable preferred orientation.
Macroscopic Shear Banding in an Aluminum-Based Alloy During Equal-Channel Angular Pressing
Authors: Wang Jingtao , Xu Yuzhong , Wang Lizhong , Zhao Xicheng , Wang Haibo 
Published: April 2011

ABSTRACTEqual-channel angular pressing is now recognized as an effective technique for fabricating materials with ultrafine structures. It is generally considered that the strain is homogeneously distributed in the materials after ECA pressing. The present investigation shows, however, that severe macroscopic shear band, which extends from bottom to top surface and slants to the longitudinal axis of specimen at an angle of about 45°, develops at regular intervals, with a high shear strain accommodation of about 3.7 within the band. Different families of macroscopic shear bands may cut across each other, and the total volume fraction of macroscopic shear bands may well surpass 50%.
Evaluation of Dislocation Storage by Means of Crystal Plasticity Analysis
Authors: Ohashi Tetsuya , Asakawa Kazuhisa 
Published: April 2011

ABSTRACTA numerical model of two phase metal microstructure of f.c.c. type crystal is made where a harder inclusion of a spherical shape is embedded in softer matrix. The model is subjected to a tensile load and its deformation is analyzed by a finite element crystal plasticity code. Under the tensile load, plastic slip deformation on {111}<110> slip systems take place in the matrix and the density distribution of the geometrically necessary dislocations is evaluated from the gradient of plastic shear strain on slip systems. Obtained results show not only a simple loop structure around the inclusion but also kink wall structure and some smaller loops. Details of the strucuture are discussed.
Beyond the Classroom: Educating Undergraduates in Materials Science Research and Careers via the CPIMA SURE Program
Authors: Goldman Marni , Wade Charles G. , Waller Brenda E. , Frank Curtis W. 
Published: April 2011

ABSTRACTThe Center on Polymer Interfaces and Macromolecular Assemblies (CPIMA), an NSF MRSEC and joint partnership among Stanford University, IBM Almaden, and University of California at Davis, established the Summer Undergraduate Research Experience (SURE) Program in 1995. Its mission is twofold: to expose undergraduate students to cutting-edge research and to help students with their ultimate career decisions. Approximately twenty-five students each summer are assigned a research project under the direction of a mentor. Students are exposed to a variety of research environments including universities, industry, and laboratories overseas. Regardless of site, students participate in research group meetings and learn the research process –a valuable experience that is often not obtained during a student's undergraduate years. To complete the research experience, SURE students attend a CPIMA Forum where they present posters on their research and interact with members of both academia and industry. While undergraduates are exposed to academia, they are often not exposed to industry or alternative careers. SURE students learn about industrial research by visiting IBM and getting a tour of the Almaden Research Center. A Career Day is held during the Program where students are given workshops on applying to graduate school as well as talks from people in different scientific careers, both traditional and nontraditional. Assessment surveys show that after their exposure to a number of experiences and ideas over 10 weeks, the SURE students have learned important lessons that a traditional classroom does not afford. To date, over 150 students have participated.
Scientists as Mentors to Science Teachers
Authors: Goodchild Fiona , Johnston Carol 
Published: April 2011

ABSTRACTThis study of teacher researchers and mentor scientists at the Materials Research Laboratory at UCSB takes a socio-cultural perspective, assuming group norms in terms of language and practice associated with being a science teacher and a research scientist. The paper will report on data gathered from individual interviews with 6 science teachers and their mentor scientists, before and after the RET six week session in summer 2000. The interviews reveal some of the expectations and benefits expressed by teachers and scientists as well as some of the contrasts in the cultures of science teaching and research science. These factors need to be accommodated in RET project design.
Evaluating Science Research Experience For Teachers Programs and Their Effects on Student Interest and Academic Performance: A Preliminary Report of an Ongoing Collaborative Study by Eight Programs
Authors: Dubner Jay , Silverstein Samuel C. , Carey Nancy , Frechtling Joy , Busch-Johnsen Tamra , Han Jeannie , Ordway George , Hutchison Nancy , Lanza Janet , Winter Jim , Miller Jon , Ohme Paul , Rayford James , Weisbaum Kathryn Sloane , Storm Kaye , Zounar Elda 
Published: April 2011

ABSTRACTFormal programs that provide research experiences for teachers (RET) have been in existence for more than 20 years. Currently there are more than 70 formalized Scientific Work Experiences Programs for Teachers (SWEPTs) nationwide. The underlying assumption of most RETs is that these intensive summer work immersion experiences, coupled with appropriate follow-up activities during the school year, expand teachers' professional skills and networks, and thereby improve the performance of their students. Many SWEPTs have collected anecdotal evidence indicating their program's positive impact on teachers. Missing from all SWEPT evaluations is quantitative evidence that teacher participation in these programs affects student interest and performance in the subject taught by the SWEPT teacher. As professional evaluators attest, it is difficult to differentiate the roles of teachers and teaching practices in changing student academic interest and performance from other factors (e.g., curriculum, school administration, non-random assignment of students, etc.).This study controls for many of these factors by comparing interest and achievement of students in classes of SWEPT teachers with students in classes of comparison teachers in the same school and teaching the same subject. The study's longitudinal design is commensurate with the philosophy and practices of the participating SWEPTs.
Imprint in Ferroelectric Thin Films Caused by Screening of an Electric Field in a Thin Surface Layer
Authors: Grossmann Michael , Lohse Oliver , Bolten Dierk , Boettger Ulrich , Waser Rainer 
Published: April 2011

AbstractImprint describes an aging effect in ferroelectric thin films which manifests itself by a shift of the P-V hysteresis loop on the voltage axis. In this paper a mechanism is described which attributes imprint to the screening of a large electric field within a thin surface layer by electronic charges. The field at the surface arises due to the existence of a thin surface layer in which the spontaneous ferroelectric polarization is suppressed. In the course of aging this field is gradually screened by electronic charges which are generated by a Frenkel-Poole effect and then become trapped near the electrode-thin-film interface causing the shift of the hysteresis loop. A numerical simulation based on this model allows a quantitative description of the imprint effect as a function of various experimental parameters.
Ferroelectric-Gate Structures and Field-Effect Transistors Using (Bi,La)4Ti3O12 Films
Authors: Tokumitsu Eisuke , Suzuki Takuya , Sugita Naoki 
Published: April 2011

AbstractWe have fabricated and characterized metal-ferroelectric-metal-insulator-semiconductor (MFMIS) diodes and field-effect-transistors (FETs) using (Bi,La)4Ti3O12 (BLT) films. 9-nm-thick SiO2 is used as an “I” layer. It is shown that the memory window in the capacitance-voltage (C-V) characteristics of the MFMIS structures is as large as 3V for a voltage sweep of 5V, when the area ratio of the MIS region (SI) to the ferroelectric capacitor region (SF), SI/SF, is 15. It is also demonstrated that the MFMIS-FETs using Pt/BLT(150nm)/Pt/SiO2(9nm)/Si structures have hysteresis loops due to the ferroelectric BLT film in the drain current-gate voltage (ID-VG) characteristics. Observed threshold voltage shift is 3V and excellent data retention characteristics are demonstrated for the device with an area ratio SI/SF of 15.
Investigation of the Role of Carbonylchemistry to Pattern Platinum Electrodes
Authors: Schneider St. , Kohlstedt H. , Waser R. 
Published: April 2011

AbstractNoble metals like platinum or irdium are used as electrode materials in DRAM or FRAM devices. Their etch process is a challenge as conventional, sputter driven etch processes either result in redeposition problems (fences) or in a severe sloping (loss of dimension control) and are not acceptable for high density integration architectures. The high temperature etch regime offers a solution by increasing the chemical etch component and thus the volatility of the etch products.As previously reported, the platinum etch rate increases exponentially for a chlorine etch process with increasing wafer temperature. In this study we investigate the particular role of carbon monoxide in a Cl2/CO etch process. We find that carbon monoxide additions to a chlorine process boost the chemical component of the platinum etch rate very significantly, exceeding the effects in the chlorine only process regime by far. Additionally we compare these results with a Cl2/O2 and a Cl2/CO2 process chemistry, which are not found to be particularly beneficial.To better understand the etch process we use an energy dispersive quadrupole mass spectrometer for in situ monitoring, attached to the chamber at two different locations. We are able to position the probe orifice at the place of the wafer electrode, to record ion energy and ion mass spectra of species impinging on the wafer plane. A second off axis position allows for etch product monitoring.
Analysis of Alternating Current Conduction and Impedance Spectroscopy Study of BaBi2Nb2O9 Thin Films
Authors: Laha Apurba , Saha S. , Krupanidhi S. B. 
Published: April 2011

AbstractAlternating current conduction in BaBi2Nb2O9 (BBN) thin films has been studied over a wide range of temperatures and frequencies. A power law relation was used to explain the frequency dependence of ac conductivity. In the higher frequency region, ac conductivity of the BBN thin films was temperature independent. The activation energy calculated from the Arrhenius plot of ac conductivity was found to be around 0.25 eV. It was attributed to shallow trap controlled space charge conduction in the bulk of the sample. The impedance analysis of the BBN thin films was also performed to gain insight into the microstructure of the films, including the characteristics of the grains, grain boundaries, and film-electrode interface. The response of a single RC combination has been observed for our case. The effect of other components, such as the grain boundary interface and electrode/film interface was negligible. The imaginary component of impedance (Z”) exhibited different peak maxima at different temperatures. A Debye mechanism was found to be appropriate to explain the polarization relaxation in BBN thin films.
Impact of Template Layers on Dielectric and Electrical Properties of Pulsed-Laser Ablated Pb(Mg1/3 Nb2/3)O3 - PbTiO3 Thin Films
Authors: Laha Apurba , Saha S. , Krupanidhi S. B. 
Published: April 2011

AbstractA study was done on pulsed laser deposited relaxor ferroelectric thin films of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) deposited on platinized silicon substrates with template layers to observe the influence of the template layers on physical and electrical properties. Initial results, showed that perovskite phase (80% by volume) was obtained through proper selection of the processing conditions on Pt/Ti/SiO2/Si substrates. The films were grown at 300°C and then annealed in a rapid thermal annealing furnace in the temperature range of 750-850°C to induce crystallization. Comparison of the films annealed at different temperatures revealed a change in crystallinity, perovskite phase formation and grain size. These results were further used to improve the quality of the perovskite PMN-PT phase by inserting thin layers of TiO2 on the Pt substrate. These resulted in an increase in perovskite phase in the films even at lower annealing temperatures. Dielectric studies on the PMN-PT films show very high values of dielectric constant (1300) at room temperature, which further improved with the insertion of the template seed layer. The relaxor properties of the PMN-PT were correlated with Vogel-Fulcher theory to determine the actual nature of the relaxation process.
Microstructural and Dielectrical Properties for Ceramics and Thin Films of the xPbTiO3-(1−x)SrTiO3 Solid Solution
Authors: Martínez E. , Fundora A. , Blanco O. , García S. , Heredia E. , Siqueiros J. M. 
Published: April 2011

AbstractSrTiO3 and PbTiO3 perovskites are combined to form the xPbTiO3-(1−x)SrTiO3 (PST) solid solution. The effect of the PbTiO3 content on the microstructural and dielectric properties is studied for different compositions (x=0.1,0.3,0.5,0.7, and 0.9). Microstructural features of the PST system are studied by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques. Electrical properties are studied by the thermoelectric analysis technique at both fixed frequency and varying frequency to study the behavior of the dielectric constant and dielectric loss.Films of 0.5PbTiO3-0.5SrTiO3 (PST50) have been obtained by RF ion sputtering on different substrates. We investigate the relation between the crystalline structure and the dielectric properties of PST50 films deposited on different metallic films. Scanning Electron Microscopy (SEM) and X-Ray Diffraction were used for the structural analysis of the PST50/TiN/Si and PST50/RuO2/TiN /Si systems. The dielectric properties of the PST50 films were measured for TiN/PST50/TiN/Si, and RuO2/PST50/RuO2/TiN/Si capacitors and the results were correlated to the structure and composition. The charge storage capabilities of the PST50 films are evaluated for possible application in integrated circuit technology.
Interdigital Ag(Ta,Nb)O3 thin Film Capacitors on Sapphire
Authors: Koh Jung-Hyuk , Grishin Alex , Shibuya Akira , Okuyama Masanori 
Published: April 2011

AbstractPolycrystalline 0.4 μm thick films of Ag(Ta,Nb)O3 (ATN) were grown on sapphire (Al2O3-0112, r-plane) wafers by pulsed laser deposition technique. 2 and 4 μm gap interdigital capacitors were defined by photolithography on the top of Au/Cr/ATN(0.4μm)/Al2O3 film structures. They exhibit high dielectric performance. In the frequency range of 1 kHz to 1 MHz dielectric permittivity shows frequency dispersion as low as 3.5 %, loss tangent ∼ 0.0035 @ 1 MHz, Kfactor = tunability/tan δ is about 20.2 @ 200 kV/cm, and resistivity as high as 1.8 × 1011 ×cm @ 100 kV/cm. C-V and I-V characteristics recorded in time domain revealed slow Curie-von Schweidler-type relaxation of the polarization. Low frequency dispersion and loss, high tunability and low noise in the biased state promise thin ATN film capacitors for microwave applications.
RF-Magnetron Sputtered Au/(Na,K)NbO3/SiO2/Si MFIS-diode Structures
Authors: Shibuya Akira , Koh Jung-Hyuk , Grishin Alex , Kugler Veronika , Music Denis , Helmersson Ulf , Okuyama Masanori 
Published: April 2011

AbstractRecently we proposed ferroelectric sodium potassium niobate (Na0.5K0.5NbO3, NKN) thin films to be a candidate for applications in nonvolatile memories and electrically tunable devices [1-5]. In this paper we report on processing and characterization of metal-ferroelectric-insulatorsemiconductor (MFIS) diode structures based on RF-magnetron sputtered NKN films. 0.7 μm thick NKN films have been deposited at 650 °C on the thermally grown 47 nm thick SiO2 layer on Si(001) wafers. Stoichiometric Na0.5K0.5NbO3 ceramic target was sputtered in an O2-Ar atmosphere with a total pressure of 5 mTorr. Grown films were analyzed as deposited as well as after an oxygen annealing at 600 °C for 30 minutes. The NKN films exhibit a strong (001) preferential orientation, which was appreciably improved after the oxygen annealing. A leakage current density of 2.3 nA/cm2 at an electric field of 400 kV/cm, and a memory window of 7.2 V was measured for Au/NKN/SiO2(47nm)/Si(001) diode structures at the programmable voltage of 40 V. I-V measurements were performed in the time domain to distinguish between the relaxation of polarization, “true” leakage current, and the degradation of the resistance in ferroelectric NKN film.
Structural and Ferroelectric Properties of Epitaxial PbZr0.52Ti0.48O3 and BaTiO3 Thin Films Prepared on SrRuO3/SrTiO3(100) Substrates
Authors: Contreras J. Rodríguez , Schubert J. , Poppe U. , Trithaveesak O. , Szot K. , Buchal Ch. , Kohlstedt H. , Waser R. 
Published: April 2011

AbstractWe have prepared single crystalline epitaxial PbZr0.52Ti0.48O3 (PZT) and BaTiO3 (BTO) thin films on single crystalline epitaxial SrRuO3 (SRO) thin films grown on SrTiO3 (100) (STO) substrates. PZT and SRO thin films were grown using high-pressure on-axis sputtering and BTO using pulsed laser deposition (PLD). The film thickness ranged between 12 to 165 nm. Their excellent structural properties, surface smoothness and interface sharpness were demonstrated by X-Ray Diffraction measurements (XRD), High Resolution Transmission Electron Microscopy (HRTEM) and Atomic Force Microscopy (AFM). Rutherford Backscattering Spectrometry and Channeling measurements (RBS/C) were used to analyze stoichiometry and crystalline quality. Ferroelectric hysteresis loops were obtained for all films of a thickness down to 12 nm showing a decrease in the remanent polarization Pr and an increase in the coercive field Ec towards thinner film thicknesses. Furthermore we have prepared tunneling junctions with a PZT or BTO barrier thickness of 3-6 nm. Reproducible bi-stable I-V-curves and bias dependence of the conductance were obtained suggesting an influence of the ferroelectric properties of the barrier material on the tunnel current.