New planar process for 2µm bubble devices with thin film detector

Conventional 2 μm bubble devices with thin permalloy detector have been successfully fabricated using a new planar process. Spacer layer undulation due to underlying conductor patterns is reduced by an organic fluid spin coating, followed by coated layer contour transformation by ion-beam etching. The spacer layer step reduction depends on ion-beam incidence angle. For sputter deposited SiO
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spacer and spin coated AZ 1350J resist, optimum reduction is obtained at 30° beam angle. Detector figure of merit for a 300 Å thick, 2 μm wide permalloy detector is found to be 1.8% at 25°C. Temperature coefficient for output voltage is -0.36%/°C at 25°C. The output voltage does not depend on drive field amplitudes ranging from 30 to 70 Oe. A 256 kbit chip fabricated using the planar process shows an overall bias margin of 30 Oe at 55 Oe drive field amplitude.