Fabrication of contiguous-disk magnetic bubble devices

A complete fabrication process has been developed for contiguous-disk magnetic bubble devices with 1-μm bubbles. Epitaxial growth of double-layer garnet films offer distinct advantages over the single-layer structure. A recent development of the self-aligned structure relaxes the lithography requirements to three levels of masking with typical alignment tolerances of ±1 μm. Metallization and patterning of the functional components are carried out by additive process for the conductor-implantation pattern and a subtractive process for the sensor. Passivation of the evaporated sensor was found to be necessary to minimize the stripe coercivity. Suitable conditions for ion implantation have been determined to be He⁺ions with the typical dose of 3 × 10¹⁵atom/cm², followed by an annealing treatment. Double implantation at 195 keV with 3.5 × 10¹⁵atom/cm²and 135 keV with 1.5 × 10¹⁵atom/cm²yields good propagation margins without requiring an additional anneal.