4,020 research outputs found
Wafer level reliability for high-performance VLSI design
As very large scale integration architecture requires higher package density, reliability of these devices has approached a critical level. Previous processing techniques allowed a large window for varying reliability. However, as scaling and higher current densities push reliability to its limit, tighter control and instant feedback becomes critical. Several test structures developed to monitor reliability at the wafer level are described. For example, a test structure was developed to monitor metal integrity in seconds as opposed to weeks or months for conventional testing. Another structure monitors mobile ion contamination at critical steps in the process. Thus the reliability jeopardy can be assessed during fabrication preventing defective devices from ever being placed in the field. Most importantly, the reliability can be assessed on each wafer as opposed to an occasional sample
Nanomechanical morphology of amorphous, transition, and crystalline domains in phase change memory thin films
In the search for phase change materials (PCM) that may rival traditional
random access memory, a complete understanding of the amorphous to crystalline
phase transition is required. For the well-known Ge2Sb2Te5 (GST) and GeTe (GT)
chalcogenides, which display nucleation and growth dominated crystallization
kinetics, respectively, this work explores the nanomechanical morphology of
amorphous and crystalline phases in 50 nm thin films. Subjecting these PCM
specimens to a lateral thermal gradient spanning the crystallization
temperature allows for a detailed morphological investigation. Surface and
depth-dependent analyses of the resulting amorphous, transition and crystalline
regions are achieved with shallow angle cross-sections, uniquely implemented
with beam exit Ar ion polishing. To resolve the distinct phases, ultrasonic
force microscopy (UFM) with simultaneous topography is implemented revealing a
relative stiffness contrast between the amorphous and crystalline phases of 14%
for the free film surface and 20% for the cross-sectioned surface. Nucleation
is observed to occur preferentially at the PCM-substrate and free film
interface for both GST and GT, while fine subsurface structures are found to be
sputtering direction dependent. Combining surface and cross-section
nanomechanical mapping in this manner allows 3D analysis of microstructure and
defects with nanoscale lateral and depth resolution, applicable to a wide range
of materials characterization studies where the detection of subtle variations
in elastic modulus or stiffness are required
Function-based Intersubject Alignment of Human Cortical Anatomy
Making conclusions about the functional neuroanatomical organization of the human brain requires methods for relating the functional anatomy of an individual's brain to population variability. We have developed a method for aligning the functional neuroanatomy of individual brains based on the patterns of neural activity that are elicited by viewing a movie. Instead of basing alignment on functionally defined areas, whose location is defined as the center of mass or the local maximum response, the alignment is based on patterns of response as they are distributed spatially both within and across cortical areas. The method is implemented in the two-dimensional manifold of an inflated, spherical cortical surface. The method, although developed using movie data, generalizes successfully to data obtained with another cognitive activation paradigmāviewing static images of objects and facesāand improves group statistics in that experiment as measured by a standard general linear model (GLM) analysis
Farmland Prices
land, price, Ontario, Canada, Agricultural and Food Policy, Agricultural Finance, Demand and Price Analysis, Land Economics/Use,
Increasing incidence of dementia in the oldest old: evidence and implications
The oldest old are the fastest growing segment of the US population but accurate estimates of the incidence of dementia in this age group have been elusive. Corrada and colleagues present data on the 5-year age-specific rates of dementia incidence in persons 90 years and older from The 90+ Study. Their findings show a continued exponential increase in dementia incidence after age 90 that mirrors the increase observed in persons aged 65 to 90, with a doubling every 5.5 years. This contrasts with previous smaller studies reporting a slowing of the increase in incidence after age 90. If confirmed, the continued increase, rather than a plateau, in the incidence of dementia in the oldest old has implications for proper healthcare planning. Strategies for prevention and treatment will require more information regarding risk factors and the etiopathogenesis of dementia in the oldest old
Thermal kinetic inductance detectors for ground-based millimeter-wave cosmology
We show measurements of thermal kinetic inductance detectors (TKID) intended
for millimeter wave cosmology in the 200-300 GHz atmospheric window. The TKID
is a type of bolometer which uses the kinetic inductance of a superconducting
resonator to measure the temperature of the thermally isolated bolometer
island. We measure bolometer thermal conductance, time constant and noise
equivalent power. We also measure the quality factor of our resonators as the
bath temperature varies to show they are limited by effects consistent with
coupling to two level systems.Comment: 8 pages, 4 figures. Submitted to Journal of Low Temperature Physic
Photon number resolving detection using time-multiplexing
Detectors that can resolve photon number are needed in many quantum
information technologies. In order to be useful in quantum information
processing, such detectors should be simple, easy to use, and be scalable to
resolve any number of photons, as the application may require great portability
such as in quantum cryptography. Here we describe the construction of a
time-multiplexed detector, which uses a pair of standard avalanche photodiodes
operated in Geiger mode. The detection technique is analysed theoretically and
tested experimentally using a pulsed source of weak coherent light.Comment: 20 pages, 14 figures, accepted to Journal of Modern Optic
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