Effects of a dielectric material in an ion source on the ion beam current density and ion beam energy.
To understand a strong focusing phenomenon that occurs in a low-energy hydrogen ion beam, the electron temperature, the electron density, and the space potential in an ion source with cusped magnetic fields are measured before and after the transition to the focusing state using an electrostatic probe. The experimental results show that no significant changes are observed before or after the transition. However, we found unique phenomena that are characterized by the position of the electrostatic probe in the ion source chamber. Specifically, the extracted ion beam current density and energy are obviously enhanced in the case where the electrostatic probe, which is covered by a dielectric material, is placed close to an acceleration electrode.
A Study on the Improvement of Etch Uniformity in an Ion Beam Etcher with a Magnetized Inductively Coupled Plasma Source
Abstract— A magnetized inductively coupled plasma ion beam etcher (MICP-IBE) was designed by employing electromagnets around the etcher (IBE). A magnetic field can be set up such that the magnitude of the magnetic flux density on the screen grid increases or decreases with the radial distance from the screen grid center. Four different types of magnetic field conditions were considered. The plasma densities and electron temperatures were measured as functions of radial distance from the screen grid center under each condition. In addition, ion flux was measured with respect to radial distance from the substrate center using ion energy analyzer (IEA), after which the uniformity characteristics of the ion flux in the substrate were investigated. The dry etching characteristics of CoFeB, a typical alloy being used in the magnetic memory device, were investigated. The uniformity characteristics of the ion flux and the etch rate can be improved with the proper design of magnetic field conditions; however, the improvement was confirmed to be limited. In this respect, a new screen and acceleration grid were designed that have different grid hole densities with radial distance from the grid center (hereafter referred to as the proposed grid). Using the proposed grid, the ion flux and etch rate of CoFeB were measured with respect to radial distance from the substrate center, to see if the radial etch rate uniformity can be improved further. The CoFeB etch rate non-uniformity in the proposed grid (11.65%) was lower than that for the conventional grid (17.5%).
Pharmacokinetics of Mivacurium Isomers and Their Metabolites in Healthy Volunteers after Intravenous Bolus Administration
Background Previous studies report the pharmacokinetics of mivacurium isomers after an infusion using venous blood sampling. Although the extent of the mivacurium arterial‐venous gradient is not known, the sampling site is likely to influence mivacurium pharmacokinetic parameters because the drug is rapidly metabolized as it traverses the circulation. The objectives of this study were (1) to determine the pharmacokinetics of mivacurium isomers in healthy persons after intravenous bolus administration using intensive arterial blood sampling, and (2) to characterize the formation and elimination of mivacurium metabolites in human plasma. Methods Eight persons classified as American Society of Anesthesiologists physical status 1 or 2 who were scheduled to undergo elective surgery under balanced anesthesia received 0.15 mg/kg mivacurium chloride as an intravenous bolus. Arterial blood samples were collected every 10 s during the first 2 min and at frequent intervals for 4 h thereafter. Plasma concentrations of mivacurium isomers and their metabolites were determined by two stereoselective high‐performance liquid chromatographic methods coupled with fluorometric detection and noncompartmental pharmacokinetic parameters. Results Mean elimination half‐lives of the trans‐trans, cis‐trans, and cis‐cis isomers were 2.4, 2, and 28.5 min, respectively, with corresponding mean plasma clearances of 29.2, 45.7, and 6.7 ml [center dot] min‐1 [center dot] kg‐1. The volumes of distribution at steady state of the trans‐trans, cis‐trans, and cis‐cis isomers were 0.047, 0.054, and 0.189 l/kg, respectively. Plasma concentrations of monoester and alcohol metabolites peaked 25 s (median) after mivacurium injection, with half‐lives in the range of 90 min, except for the cis alcohol metabolite, which was only negligibly and transiently formed. Conclusions Substantial hydrolysis of mivacurium isomers by cholinesterases was confirmed by the rapid appearance of mivacurium metabolites in plasma. The intensive arterial sampling proved to be critical for the trans‐trans and cis‐trans isomers because the area under the curve between 0 and 2 min accounted for 75% and 86% of the total, respectively.