Electrodeposited cylindrical magnetic film memory technology is reviewed. Extensive references are made to previous work. New data is given in areas not previously reported. Special emphasis is given to the following items: 1) Applications: Plated-wire applications cover the spectrum from 100 to 1000 ns cycle time NDRO memories of 105to 107bits capacity in commercial and military markets. 2) Processing: Substrate preparation and electrochemical processing, as well as alternative magnetic plating solutions, and the control of pH, temperature, flow rate, Ni-Fe ratio, and other variables necessary for high yield plating are reviewed. 3) Aging: The conditions that stabilize the film and the test methods that predict a 10- to 100-year life are reviewed. 4) Testing: A practical approach to continuous production line testing is reviewed. 5) Bit Packing Density: Calculations on magnetization distribution along the wire are compared to experience. Although memory plane geometry is important, the wire characteristics dominate the achievable bit density. Wire diameter, film thickness H k , and other factors are included in graphs useful for design purposes. 6) Memory Plane Construction: The relative advantages of several different forms are compared. The need for magnetic keepers and their advantages are reviewed. 7) Interactions: New data is presented on some of the effects of variations in word strap alignment and spacing as well as the sensitivity to variation in plated-wire spacing and bending.

Plated-wire technology: A critical review

A review and critique is made of those material and processing issues that pertain to the implementation of micrometer and submicrometer bubble devices on amorphous films. Adequate reproducibility and uniformity have been achieved in ternary amorphous films prepared by rf sputtering and their magnetic characteristics are very similar to those of analogous garnet films. Factors that may limit application to the amorphous films include defects and dielectric breakdown in insulating layers, sensitivity to annealing, and larger, but not prohibitive, coercivities. A salient problem common to both garnet and amorphous materials is attainment of sufficiently large values of Q to ensure stable device operation.

Amorphous materials for micrometer and submicrometer bubble domain technology

A new field‐access bubble detector is described and assessed in terms of signal‐strength propagation margins and technology benefits. In this design the detection and propagation functions of the detector are separated by means of a sandwich structure. The so‐called sandwich detector consists of a thin NiFe layer (detection), an insulation layer of SiO2, and a thick NiFe layer (propagation). The layers are structured with the aid of one mask (no alignment) while two gross masks (alignment accuracy within 25 μm) are used to create the connections to the detection layer. The measured sensitivity of a 35‐chevron stretcher sandwich detector, designed for 7‐μm bubbles (4π Ms=150 G), is 2 mV/mA.

A highly sensitive magnetic bubble detector in an essentially single‐mask overlay

Using fast response detecting and recording equipment the breakdown voltage spectra of thin film dielectrics (with a GdCoMo first electrode and permalloy counter-electrode) were measured as a function of time and temperature during application of linearly increasing (ramp) voltages. For 1000 A thick SiO 2 films the dielectric breakdown events occurring at high voltages were seen to be strictly voltage-dependent, whereas those breakdowns occurring at low voltages exhibited a definite time-dependence in addition to a voltage-dependence. In this low voltage region slowly increasing voltages (low ramp rates) resulted in significantly greater numbers of cumulative failures, for a given attained voltage, than did rapidly increasing voltages. This time-dependence, transformed through a simple kinetic power law to a constant applied voltage experiment was found to be consistent with Peek's law of dielectric breakdown. The data and analysis suggest that reliable device operation will not be achieved if electric fields in excess of 0.6 × 106V/cm are applied across the dielectric.

S. Tan

Papers

Dielectric reliability in amorphous film bubble devices

Annealing of magnetic films in a rotating field