Thin-gate oxides prepared by pure water anodization followed byrapid thermal densification

Anodic oxidation at room temperature with pure deionized water as electrolyte and then followed by high-temperature rapid thermal densification was used to prepare high breakdown endurance thin-gate oxides with thicknesses of about 50 Å. It was observed that the oxides prepared by anodic oxidation followed by rapid thermal densification (AOD) show better electrical characteristics than those grown by rapid thermal oxidation (RTO) only. The AOD oxides have a very low midgap interface trap density, Ditm, of smaller than 1×10¹⁰ eV^-1 cm^-2 and negative effective oxide trapped charge. From the smaller leakage currents observed during staircase ramp voltage time-zero dielectric breakdown (TZDB) and constant field time-dependent dielectric breakdown (TDDB) testings, it is supposed that the uniform interfacial property and the pretrapped negative charges in AOD oxides are responsible for the improved characteristics     

Effect of epitaxial realignment on the leakage behavior of arsenic-implanted,as-deposited polycrystalline Si-on-single crystal Si diodes

When dopants are indiffused from a heavily implanted polycrystalline silicon film deposited on a silicon substrate, high thermal budget annealing can cause the interfacial “native” oxide at the polycrystalline silicon-single crystal silicon interface to break up into oxide clusters, causing epitaxial realignment of the polycrystalline silicon layer with respect to the silicon substrate. Anomalous transient enhanced diffusion occurs during epitaxial realignment and this has adverse effects on the leakage characteristics of the shallow junctions formed in the silicon substrate using this technique. The degradation in the leakage current is mainly due to increased generation-recombination in the depletion region because of defect injection from the interface.     

Gate and drain currents in off-state buried-type p-channel LDDMOSFETs

The buried-type p-channel LDD MOSFETs biased at high positive gate voltage exhibit novel characteristics: (1) the ratio of the drain to gate currents is about 1×10^-3 to 5×10^-3; and (2) the gate and drain currents both are functions of only the gate voltage minus the n-well bias. Such characteristics are addressed based on the formation of the surface n ⁺ inversion layer due to the punchthrough of the buried channel to the underlying shallow p-n junction. The measured gate current is due to the Fowler-Nordheim tunneling of electrons from this inversion layer surface and the holes generated within the high-field oxide constitute the drain current. The n⁺ inversion layer surface potential is found to be equal to the n-well bias plus 0.55 V. As a result, both the oxide field and the gate and drain currents are independent of drain voltage     

Practical stopping criteria for validating safety-critical software by estimating impartial reliability

In this research, we investigate stopping rules for software testing and propose two stopping rules from the aspect of software reliability testing based on the impartial reliability model. The impartial reliability difference (IRD-MP) rule considers the difference between the impartial transition-probability reliabilities estimated for both software developer and consumers at their predetermined prior information levels. The empirical–impartial reliability difference (EIRD-MP) rule suggests stopping a software test when the computed empirical transition reliability is tending to its estimated impartial transition reliability. To insure the high-standard requirement for safety-critical software, both rules take the maximum probability (MP) of untested paths into account.     

Design model and guidelines for n-well guard ring in epitaxial CMOS

This work reports the development of design model for n-well guard rings in a CMOS process utilizing a low-doped epitaxial layer on a highly doped substrate. The validity of the model has been judged by a wide range of experimental data measured from the fabricated n-well guard ring structures with guard ring width as parameter. From the model developed, guidelines have been drawn to minimize the guard ring width while critically suppressing the amount of electrons escaping from the guard ring     

The base current degradation of poly-emitter BJTs under AC stress

A simple model for the analysis of the ac stress effect in poly-emitter bipolar transistors is presented. Apart from the reverse-bias induced hot-carrier effects, the forward-bias recovery effect is a key factor under ac stress, it obviously suppresses the base current degradation of the device which is caused during the reverse-bias periods. In this work, we derived the relationship between the excess base current and the stress time for different ac stress conditions. This model is verified with experimental results.<>     

Size of Micelles Determined by Static Fluorescence Quenching

We developed a new method to measure the average aggregation number of large rod-like micelles using static fluorescence self-quenching of a solubilized fluorophore. The method is based on the increase of self-quenching of micelle-solubilized pyrene through excimer formation. We consider the effect of random distribution of pyrene in micelles and the micellar size distribution. The measured average aggregation <n> _M is based on a new M-weighted raging similar to our exponential-weighted averaging in the transient decay method. We apply this method to study the effect of a large concentration of salt on the average aggregation behavior of sodium dodecyl sulfate (SDS) and cetyle tetraammonium bromide (CTAB). The sizes increase with increasing ionic concentrations. For SDS, we used the thermodynamic model developed by Missel et al. to calculate < n > _M which we compare with experimental results.     

Temporal Response of SERS to the Potential for 4-Cyanopyridine Adsorbed on Ag Electrode

Time-resolved surface-enhanced Raman scattering (SERS) was applied to study the response of Raman bands from 4-cyanopyridine (PyCN) adsorbed on a Ag electrode to variation of the potential; the temporal resolution was 0.1 s. The response of the SERS signals of PyCN was instantaneous to the oxidation potential of Ag electrode. However, delay of the SERS signals was observed while AgCl was reducing. The decay and growth of the SERS bands look place within 1 s in the cases of desorption and adsorption of PyCN on the electrode. It took much longer for PyCN to alter from one adsorption geometry to another on the electrode.     

Optically clear simultaneous interpenetrating polymer networks based on poly(ethylene glycol) diacrylate and epoxy. I. Preparation and characterization

Poly(ethylene glycol) diacrylate was synthesized from poly(ethylene glycol) of molecular weight 600 with acryloyl chloride in a molar ratio of 1:2. Poly(ethylene glycol) diacrylate (PEGDA) was then blended with diglycidyl ether of bisphenol A (DGEBA) in various ratios, followed by curing with 2,2′-azobisisobutyronitrile (AIBN) and isophronediamine (IPDA) simultaneously. Viscosity changes before and during IPN formation were examined with a Brookfield viscometer. Formation of H-bonding and functional group changes were investigated with FTIR. Exothermic curing thermograms were recorded with dynamic DSC. Optically clear IPNs thus obtained were characterized with rheometric dynamic spectroscopy (RDS) and scanning electron microscopy (SEM) to check possible compatibility of the two networks. Experimental results revealed that during IPN formation hydrogen bonds between PEGDA and DGEBA and interlock of networks had profound effect on viscosity change and pot-life. Complete compatibility of the IPNs was found as DGEBA content was higher than 50% by weight. The compatibility between PEGDA and DGEBA networks was evidenced from inner shift of a single damping peak in RDS. In the meantime, SEM micrographs confirmed the coincidence with the result of RDS © 1992 John Wiley &Sons, Inc.     

Voltammetric study of copper(I) thioacetamide complexes

Summary The composition and stability of copper(I) complexes with thioacetamide (TAA) have been evaluated with the help of square-wave voltammetry using the fast pulse technique. Two species, namely Cu(I) (TAA) and Cu(I) (TAA)₂, have been identified having the formation constants log ₁=16.85; log ₂=18.03. The complex is stable in highly acidic medium (pH1). The application for the determination of copper is pointed out.