The effect of deposition temperature on the material and electrical properties of PZT thin films for ULSI DRAM applications

Abstract

The effects of deposition temperature on the properties of thin films of sputtered lead-zirconate-titanate (PZT) have been studied for ULSI DRAM storage capacitor dielectric applications. The films were deposited by reactive dc magnetron sputtering from a multi-component target. The grain size for the films deposited at 400°C was found to be less than 1000 Å, while it was ～ 10–30 μm for films deposited at 200°C. Small grain-sized material is desirable since it leads to better cell-to-cell uniformity in terms of charge storage capacity and other electrical and reliability properties. The optimum lead compensation was found to increase as the deposition temperature (T _dep) increased. Leakage current density stays fairly constant as T _dep is varied. As-deposited films, with a deposition temperature of 500°C, were rich in the perovskite phase and showed a high charge storage density of 11.2 μC/cm² and a low leakage current density of 5.1 × 10^?7 A/cm² (both at 1.5 V). This implies the possibility of eliminating the high temperature crystallization-annealing step.     

Enhanced saturation and subcooled boiling of FC-72 dielectric liquid

Experiments are conducted which investigated enhancements in nucleate boiling of FC-72 dielectric liquid on porous graphite and compared results with those on a smooth copper surface of the same dimensions (10 × 10 mm). Also investigated is surface temperature excursion at boiling incipience and the obtained values of CHF are compared with those of other investigators on copper, silicon, and micro-finned silicon surfaces and micro-porous coatings. Results showed no temperature excursion at boiling incipience on porous graphite but as much as 14.0 K in saturation and 9.0-13.3 K in subcooled boiling on copper. The nucleate boiling heat transfer coefficients on porous graphite are significantly higher than on copper and the values of CHF (27.3, 39.6, 49.0, and 57.1 W/cm² in saturation and at ΔT_sub = 10, 20, and 30 K, respectively) are 63-94% higher than on copper (16.9, 21.9, 26.9, and 29.5 W/cm², respectively). The surface superheats at CHF on porous graphite (11.0 K in saturation and 17.2-19.5 K in subcooled boiling) are lower than on copper (21.3 K and 22.9-24.9 K, respectively). The nucleate boiling heat transfer coefficient increase with subcooling and CHF increased linearly with ΔT_sub. The subcooling coefficient of CHF on porous graphite (0.041) is slightly smaller than those on micro-porous coatings (0.044 and 0.049) but much higher than those on micro-finned silicon surfaces (0.022, 0.036), and on Cu, Si, and enhanced SiO₂ (0.018) surfaces.     

A Simplified Methodology to Measure the Characteristic Curvature (Cc) of Alkyl Ethoxylate Nonionic Surfactants

This work introduces a simplified methodology for measuring the characteristic curvature (Cc) of commercial alkyl ethoxylate nonionic surfactants using carefully selected reference surfactants and oils that produce rapid and well defined separations in salinity scans. The Cc of the commercial reference surfactants was calculated using optimal salinities (S*) obtained from solubilization parameter curves, from interfacial tensions (for a selected system), and from emulsion stability tests. The latter provided a fast detection of S*, in a matter of minutes. The calibrated Cc of the reference surfactants was subsequently used to measure the Cc of various commercial alkyl ethoxylate surfactants. The combination of mixtures of test and reference surfactants and emulsion stability tests produced reproducible Cc values that could be obtained with simple bottle tests and in a timely manner. The values obtained using this methodology were cross‐checked, and proved to be consistent, when using different combinations of reference surfactants and oils, and when conducted by different individuals. The standard deviation of Cc from these measurements was typically ±0.2 Cc units, but it could be as large as 25 % of the Cc value for highly hydrophilic surfactants. After comparing the values of Cc obtained experimentally with values calculated from nominal structures (via a group contribution model) it became clear that there are differences between these values, likely because of the polydispersity of alkyl ethoxylate surfactants.     

Surface Morphology Studies in Polymer-Graphite/Epoxy Sliding

Ultrahigh-molecular-weight polyethylene (UHMWPE) and polycarbonate pins were slid dry against continuous graphite fiber/epoxy plates in reciprocating multiple-pass wear tests for different values of virgin surface roughness, fiber orientation, and load. Scanning electron photomicrographs of the polymer wear surfaces were combined with three-dimensional graphs of wear rate versus virgin surface roughness and fiber orientation. The types of surface damage observed for UHMWPE at both an 8.9- and 35.6-N load were mild plastic deformation, fatigue of loose particles, and light abrasive cutting. The types of surface damage observed for polycarbonate at either load were massive abrasive plowing and plastic flow of material. The wear debris of UHMWPE consisted of rolled, cut, or extruded particles; for polycarbonate, clumps of transferred plateaus of polymer. The unit pressure times velocity (PV) limit for polycarbonate was reached when samples were slid against the most abrasive counterface transverse to the graphite fibers.     

Analysis of melt-through process of 1.07 μm continuous wave high power laser irradiation on metal

Laser-metal interactions are influenced by various parameters, including laser wavelength and laser pulse duration. By proper adjustments of these parameters, one can create states that manifest different phenomena during laser ablation. In this work, we study laser melt-through of metal using 1 kW high power continuous laser with 1.07 μm wave length. A Ytterbium (Yb) doped fiber laser is used on the metal sample of varying thicknesses (0.1 ～ 2 mm). In addition to providing measurements from the melt-through process, numerical study of thermal transport effect of laser heating and thermo-elastic response of metal are reported. The test-based simulation is shown to reproduce the thermal transport characteristics of beam-metal interaction at high power continuous wave irradiation with notable accuracy.     

Social status in small groups: Individual–group similarity and the social "misfit."

Proposes that social status is a function of both individual and group characteristics and argues that 2 factors are necessary to predict peer popularity—prosocial interaction and person–group similarity. Prosocial behavior, viewed as a prerequisite for high social status, was predicted to be consistently correlated with status across peer groups. The relation between status and other social behaviors such as aggression was predicted to be mediated by the degree of similarity between the individual and the peer group. Two studies were conducted with 217 males (mean age 10 yrs) at a summer program for children with behavioral and social problems. Data from both acceptance and rejection measures of status support the proposed model. This evidence helps to integrate discrepant findings in the sociometric literature and demonstrates the utility of social psychological theories of interpersonal attraction in the study of peer status. (45 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Testing Water Mist Systems Against Large Fires in Tunnels: Integrating Test Data with CFD Simulations

The high cost of conducting large, full-scale fire tests for the evaluation of suppression systems in tunnels tends to limit both the extent of the instrumentation provided and the number of tests that are conducted. Because of the variability of the large fires, performance criteria based on single point measurements derived from experience with smaller test fires were not reliable indicators of performance. Yet decisions about the acceptability of suppression systems must be based on the limited amount of performance information available. A means was sought to reduce the reliance on single point instrumentation readings, and to augment the value of the limited amount of test data by integrating the field testing with CFD modeling. In this study a computational fluid dynamic (CFD) model was used to simulate a series of full-scale fire tests of water mist systems conducted in 2006 in a highway test tunnel. The NIST Fire Dynamics Simulator version 4 (FDS4) was used to simulate five of the tunnel fire tests. The task was to confirm that the simulations could achieve a reasonable degree of agreement with the conditions measured in the tests. The model could then be used to evaluate the performance of the water mist system over a broader range of performance indicators than were measured. This paper illustrates what is unique about very large fire tests and presents highlights of the modeling. The level of agreement between simulation and test results is demonstrated for one test. Agreement was deemed to be good enough to establish confidence in applying the model to examine the conditions that would occur with an unsuppressed fire, which had not been tested. CFD modeling can be used to improve the understanding of the performance of the suppression system, and to augment the value of the test results. A second, complementary paper has been submitted to the SFPE Journal of Fire Protection Engineering to provide more detailed information about the FDS4 modeling than can be covered in this paper.     

Design and evaluation of a robotic system for transcranial magnetic stimulation

Transcranial magnetic stimulation is a noninvasive brain stimulation technique. It is based on current induction in the brain with a stimulation coil emitting a strong varying magnetic field. Its development is currently limited by the lack of accuracy and repeatability of manual coil positioning. A dedicated robotic system is proposed in this paper. Contrary to previous approaches in the field, a custom design is introduced to maximize the safety of the subject. Furthermore, the control of the force applied by the coil on the subject's head is implemented. The architecture is original and its experimental evaluation demonstrates its interest: the compensation of the head motion is combined with the force control to ensure accuracy and safety during the stimulation.     

Coalescence of InP Epitaxial Lateral Overgrowth by MOVPE with V/III Ratio Variation

The effects of V/III ratio and seed window orientation on the coalescence of epitaxial lateral overgrowth InP over SiO₂ using metal organic vapor-phase epitaxy with tertiary butyl phosphine were investigated. Parallel lines having θ = 60° and 30° off [0[`1] \bar{1} 1] were coalesced, and their lateral growth rate variation with V/III was measured. Coalescence of lines separated by narrow angles in a star-like pattern was also studied. We find the greatest extent of coalescence to occur when the window stripe is oriented just off of the ⟨010⟩ directions. V/III ratio strongly affects the extent of coalescence, showing an alternating enhancement or inhibition depending on which side of the ⟨010⟩ direction the stripes are oriented. The variation in quality of coalesced material between stripes separated by narrow angles is examined with cross-sectional transmission electron microscopy, illustrating the most problematic growth directions under two V/III ratio conditions.