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The dependence of the ionic current density J on the mean field trueE¯ in oxides grown on tantalum in H3PO4 electrolyte was studied using ellipsometry to estimate the thickness. The field in the outer layer which is believed to grow due to metal ion motion is higher because of phosphate incorporation. The field in this layer was estimated by assuming that the field in the inner undoped layer was the same as the mean field at the same current density and temperature in films made in dilute sulfuric acid, which are less affected by electrolyte incorporation. The results indicate that the effect of phosphate on the ionic conductivity may be due to its reducing the permittivity and hence the effective field. It is pointed out that electrolyte incorporation gives two effects which contribute to the nonlinearity of log J vs. trueE¯ plots. Thus, since the metal ion transport number increases with J so does the proportion of the film which contains phosphate and requires a higher field. Also the concentration of phosphate increases with J . The incorporation leads to history effects which are not removed by subsequent formation, since the profile of phosphate records the sequence of current densities used. The time dependence of the field on changing the electrolyte is consistent with the field locally determined by the local film material.

Ellipsometric measurements on anodic oxide films grown on niobium in phosphoric acid were found to show behavior characteristic of films consisting of two layers, but films grown in chloride solution showed the behavior typical of uniform films. It was concluded that as with tantalum, phosphate but not chloride ions are taken up in the outer part of the film, which grows by metal ion motion. The logarithm of the steady‐state current density was linear in the field in the oxide for films grown in chloride solution and nonlinear for films formed in phosphate solution. It is concluded that, as with tantalum, the nonlinearity for some electrolyte solutions is caused by incorporation of electrolyte species in the outer part of the films rather than being a fundamental feature of the ionic transport process. The small signal ac response of the ionic current density was studied for both electrolyte solutions. These measurements gave information on steady‐state and stepped field kinetics and on the distribution of relaxation times involved in the transients observed when the current or field is suddenly changed. The steady‐state and stepped field admittivities from the ac + dc measurements were normalized by the dielectric permittivities of the films grown in the different solutions. © 2000 The Electrochemical Society. All rights reserved.

The anodization of Si in a 1 MHz oxygen plasma is described. In-~tu film thickness measurements were made using a single angle "s" light reflectance technique and this data, coupled with information on the variation of sample voltage with thickness, was used to determine the dependence of ionic current on oxide field strength. The data for a given oxide thickness could be described by an equation of the form given by the theory of ionic conduction by a thermally activated, field-assisted process. However, the ionic current and, in particular, the oxide field strength were dependent on oxide thickness. MOS C-V measurements on oxides of different thickness indicated a change in flatband vol%age that could be attributed to a progressive build-up of positive charge within the oxide. This space charge could be reduced by a low temperature annealing treatment. The oxides were found to be slightly absorbing optically, to have a relative permittivity in the range 3.5-3.9, and to possess good insulation properties as long as the oxide thickness did not exceed about 2500A.The formation of a thin film of SiO2 on Si is a key step in modern integrated circuit technology and, although the oxidation of Si by thermal means is well-* Electrochemical Society Active Member.established there would appear to be a need for a low temperature oxidation process that is compatible with other steps in the device-processing sequence. Plasma anodization would seem to satisfy these requirements and the technique applied to silicon has already re-) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.160.4.77 Downloaded on 2015-03-30 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.160.4.77 Downloaded on 2015-03-30 to IP

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