Ronald H. Wilson

A model for the current‐voltage curve of photoexcited semiconductor electrodes

A model to describe the behavior of photoexcited electrodes in an electrochemical cell is developed. In addition to the bulk semiconductor properties, the important parameters are a surface recombination parameter Sr and a surface electron transfer parameter St. It is the electron transfer process across the interface that leads to current in the external circuit. Using experimental curves for oxygen evolution at an n‐type TiO2 electrode and Hall‐Shockley‐Read recombination to determine Sr, it is shown that the I‐V curve in anodic bias is controlled by the competition between Sr and St. The physical basis for St is discussed and experimental approaches to investigate surface reactions are suggested.

Magnetization of Iron‐Nickel Alloys Under Hydrostatic Pressure

Magnetization measurements were made on iron, nickel, and their alloys in hydrostatic pressures up to 3000 atm and in fields up to 12 000 oe. The results of these room‐temperature measurements, combined with Patricks results on the pressure dependence of the Curie temperatures, indicate that σ0, the saturation moment at 0°K, as well as θ, the Curie temperature, is rapidly decreased by compression in the fcc alloys of about 30% Ni. This is in agreement with the recent low‐temperature pressure measurements of Kondorsky and Sedov. For these alloys, both σ0 and θ are decreasing with increasing Fe concentration. When the 30% Ni alloy is partially transformed to bcc, its σ0 and θ rise to much higher values but its magnetization is much less pressure dependent. It is concluded that unlike the more simple ferromagnetic bcc alloys, the fcc Fe‐Ni alloys have a coexistence of ferromagnetic and antiferromagnetic order, similar to that recently proposed for the Ni‐Mn alloys.

A semiconductor nonvolatile electron beam accessed mass memory

BEAMOS-beam addressed metal-oxide-semiconductor is a new technology for fast auxiliary memories which is expected to find important applications in military and commercial data systems. The concept is based on electron beam accessing, using a matrix lens, of a simple MOS memory chip. It has performance features which include large bit capacity per module (> 30 × 106bits), short access time ( 10 Mbit/s), and low cost. The BEAMOS module is all electronic, rugged, and relatively insensitive to variations in temperature, making it especially attractive for military computer applications. The operating principles of the BEAMOS memory and its present state of development are described.

Application of selective CVD tungsten for low contact resistance via filling to aluminum multilayer interconnection

Process parameters for selective chemical vapor deposition of tungsten to fill vias between aluminum or aluminum alloy multilevel metallization have been identified and demonstrated. By controlling two competing parallel reactions: Aluminum and hydrogen reductions of tungsten hexafluoride in one reduction step process, the specific contact resistivity was found to be in the range of 2.5 to 8.0 x 10−9 ohm-cm2 for 1.8 micron diameter vias. This is at least one order of magnitude lower than the values reported by the previous workers. It was also observed that alloying the aluminum did not appear to affect the contact resistance significantly. In this experiment one cold wall experimental reactor, two cold wall production systems of two different models and one hot wall tube furnace were used to deposit selective CVD tungsten on aluminum or aluminum with 1% silicon first level metal. As a consequence of these findings, problems associated with filling straight wall vias of high aspect ratio in VLSI multilevel interconnection (i.e., high contact resistance, poor step coverage, electromigration, etc.) can now be alleviated or resolved. Therefore, the use of selective CVD tungsten in the existing aluminum IC metallization becomes very attractive and feasible.

New insights on nucleation of tungsten on insulators during selective chemical vapor deposition

Selective deposition of tungsten on metals and silicon in the presence of insulators is important in several very large scale integrated circuit applications. The results of experiments investigating this selectivity are reported. The influence of the total area and composition of the selective growth surface on the nucleation of tungsten on adjacent insulators are illustrated. Specifically, nucleation is shown to occur preferentially in close proximity to the area of tungsten growth. The extent of nucleation on silicon dioxide compared to silicon nitride or phosphorus‐doped glass is dependent on the composition of the surface on which the initial selective tungsten growth occurs. The qualitative observations presented here form the basis for further quantitative investigations.

BEAMOS: a new electronic digital memory

BEAMOS, for Beam Addressed Metal Oxide Semiconductor, is a new technology for auxiliary memories based on an electron beam which reads and writes data on a simple unstructured MOS chip. It can store data for months with or without power.

Diode detection of information stored in electron‐beam‐addressed MOS structure

Charge stored in an insulating layer on a semiconductor can influence the field at the surface of the semiconductor and consequently control the surface recombination velocity. This paper describes the use of this effect to control the current in a reverse‐biased p‐n junction in the semiconductor. When an electron beam is used to write and read the stored charge, the effect can be used to produce high‐resolution high‐gain devices that have a variety of potential uses in information‐storage applications. Experiments demonstrating this effect are described.

Magnetocrystalline Anisotropy of Fe-Si Alloy Crystals under Hydrostatic Pressure

Magnetization measurements at room temperature were made for various fields applied in 〈100〉, 〈110〉, and 〈111〉 directions of 6 at. % Si in Fe alloy crystals subjected to hydrostatic pressures up to 5100 bar. All the experimental results are found to agree closely with theoretical curves computed for K1−1(∂K1/∂p) = −60, K2−1(∂K2/∂p) = 0, and σ3−1(∂σ3/∂p) = −5.5 (all in 10−7 bar−1), where the anisotropy constants K1 and K2 are 46 and 7 (in 103 erg/g), respectively, and the saturation moment σ3, is 204 emu. These values for the pressure dependences of K1 and σ3, when converted to volume dependences and combined with thermal dilatation data, can account for some but only a small part of the discrepancy between recent measurements on this alloy and the theoretical l0th-power relation between the variations of K1 and σ3 with temperature. A similar situation is shown to obtain for pure iron.