Rapid thermal annealing effects on Si p+-n junctionsfabricated by low-energy FIB Ga+ implantation

Effects of rapid thermal annealing (RTA) on sub-100 nm p⁺ -n Si junctions fabricated using 10 kV FIB Ga⁺ implantation at doses ranging from 10¹³ to 10¹⁵ cm ^-2 are reported. Annealing temperature and time were varied from 550 to 700°C and 30 to 120 s. It was observed that a maximum in the active carrier concentration is achieved at the critical annealing temperature of 600°C. Temperatures above and below the critical temperature were followed by a decrease in the active concentration, leading to a `reverse' annealing effect     

Squeezing more bits out of HTTP caches

Computer system designers often use caches to solve performance problems. Caching in the World Wide Web has been both the subject of extensive research and the basis of a large and growing industry. Traditional Web caches store HTTP responses, in anticipation of a subsequent reference to the URL of a cached response. Unfortunately, experience with real Web users shows that there are limits to the performance of this simple caching model, because many responses are useful only once. Researchers have proposed a variety of more complex ways in which HTTP caches can exploit locality in real reference streams. This article surveys several techniques, and reports the results of trace-based studies of a proposal based on automatic recognition of duplicated content     

Visa protocols for controlling interorganizational datagram flow

The increasing use of internetworking protocols to connect administratively heterogeneous networks has raised the question of how an organization can control the flow of information across its network boundaries. One method for doing so is the use of visas, a cryptographic technique for authenticating and authorizing a flow of datagrams. Two visa protocols are presented and evaluated: one that requires distributed state information in gateways and one that uses additional encryptions instead of distributed state. Applications for such visa protocols include access control, accounting and billing for packet transit, and network resource management.<>     

Building-in reliability into VLSI junctions

A nondestructive test is presented for monitoring junction quality and reliability in a manufacturing environment. Using a properly selected two-temperature measurement of the activation energy associated with reverse-biased junction leakage, it was demonstrated that the activation energy was more sensitive to slight changes in junction quality than was the commonly used method of monitoring the ideality factor. The activation energy method was found to be an effective and efficient metric for controlling normal process variation. As such, this method was found to be an excellent tool for building-in quality and reliability into junctions     

Electrical properties of Si p+-n junctions for sub-0.25μm CMOS fabricated by Ga FIB implantation

p⁺-n junction diodes for sub-0.25-μm CMOS circuits were fabricated using focused ion beam (FIB) Ga implantation into n-Si (100) substrates with background doping of N_b=(5-10)×10 ¹⁵ and N_b⁺=(1-10)×10¹⁷ cm^-3. Implant energy was varied from 2 to 50 keV at doses ranging from 1×10¹³ to 1×10¹⁵ cm^-2 with different scan speeds. Rapid thermal annealing (RTA) was performed at either 600 °C or 700°C for 30 s. Diodes fabricated on N_b⁺ with 10-keV Ga⁺ exhibited a leakage current (^I_R) 100× smaller than those fabricated with 50-keV Ga⁺. Tunneling was determined to be the major current transport mechanism for the diodes fabricated on N_b⁺ substrates. An optimal condition for I_R on N_b⁺ substrates was obtained at 15 keV/1×10¹⁵ cm^-2. Diodes annealed at 600°C were found to have an I_R 1000× smaller than those annealed at 700°C. I-V characteristics of diodes fabricated on N_b substrates with low-energy Ga⁺ showed no implant energy dependence. I-V characteristics were also measured as a function of temperature from 25 to 200°C. For diodes implanted with 15-keV Ga ⁺, the cross-over temperatures between I_diff and I_g-r occurred at 106°C for N_b ⁺ and at 91°C for N_b substrates     

Differential activation of adenosine receptors decreases N-type but potentiates P-type Ca2+ current in hippocampal CA3 neurons

Adenosine is released in the brain in significant quantities in response to increased cellular activity. Adenosine has been shown either to decrease synaptic transmission or to produce an excitatory response in hippocampal synapses, resulting in increased glutamate release. Previous reports have shown that adenosine or its analogs reduced Ca2+ current in dorsal root ganglion and hippocampal neurons. Here we show that the selective activation of adenosine receptor subtypes has different effects on Ca2+ channels from acutely isolated pyramidal neurons from the CA3 region of guinea pig hippocampus. Activation of A1 receptors inhibited primarily N-type Ca2+ current. In contrast, activation of A2b receptors resulted in significant potentiation of P-type but not N-type Ca2+ current. This potentiation could be inhibited by blocking the cAMP-dependent protein kinase. Because of the ubiquity of adenosine, the differential effects on Ca2+ channels of adenosine receptor subtype activation may have significant implications for neuronal excitability.     

Advantages of LDD-only implanted fluorine with submicron CMOStechnologies

The effect of fluorine implantation on the properties of shallow n ⁺/p junctions has been investigated. The novel approach of this work lies in the introduction of fluorine only in the LDD regions of the device and not in the active region underneath the gate. Gated diodes were used as test vehicles to study the effect of the fluorine incorporation. Gated diodes are ideal for measurements of this nature since they are sensitive to changes in the interfacial properties near the gate to diffusion overlap region. Results from electrical device characterization indicate a reduction in gated diode leakage and mid-gap interface state density as the F-implanted dose is increased without causing any significant change in the flat-band voltages. Results also showed that samples with F incorporation tended to be more robust to electrical stress than those without F. Materials analysis indicated reduced junction depths for samples with F introduced in the LDD regions indicating suppression of phosphorus dopant diffusion     

Strategies to protect bone mass in the older patient with epilepsy

The annual incidence of epileptic seizures rises dramatically after the age of 60. Risk factors associated with late-onset epilepsy include cerebrovascular disease, dementia, infection, trauma, and alcoholism. The dominant cause of seizures in older patients is a previous stroke, whereas a significant percentage of cases are attributed to the presence of a tumor. Normal aging is associated with an increased risk for fractures from trauma and osteoporosis. Antiepileptic medications may exacerbate this problem by adversely affecting bone metabolism and increasing the risk of falls related to drug toxicity. The patient work-up, careful prescribing, and monitoring for drug toxicity can help preserve bone integrity in patients receiving antiepileptic drug therapy.     

Manipulating epileptiform bursting in the rat hippocampus using chaos control and adaptive techniques

Epilepsy is a relatively common disease, afflicting 1%-2% of the population, yet many epileptic patients are not sufficiently helped by current pharmacological therapies. Recent reports have suggested that chaos control techniques may be useful for electrically manipulating epileptiform bursting behavior in vitro and could possibly lead to an alternative method for preventing seizures. We implemented chaos control of spontaneous bursting in the rat hippocampal slice using robust control techniques: stable manifold placement (SMP) and an adaptive tracking (AT) algorithm designed to overcome nonstationarity. We examined the effect of several factors, including control radius size and synaptic plasticity, on control efficacy. AT improved control efficacy over basic SMP control, but relatively frequent stimulation was still necessary and very tight control was only achieved for brief stretches. A novel technique was developed for validating period-1 orbit detection in noisy systems by forcing the system directly onto the period-1 orbit. This forcing analysis suggested that period-1 orbits were indeed present but that control would be difficult because of high noise levels and nonstationarity. Noise might actually be lower in vivo, where regulatory inputs to the hippocampus are still intact. Thus, it may still be feasible to use chaos control algorithms for preventing epileptic seizures.