Two-axis micro fluxgate sensor on single chip

Abstract

We present a two-axis micro fluxgate sensor on single chip for electronic compassing function. To measure X- and Y-axis magnetic fields, functional two fluxgate sensors were perpendicularly aligned and connected each other. The fluxgate sensor was composed of square-ring shaped magnetic core and solenoid excitation and pick-up coils. The solenoid coils and magnetic core were separated by benzocyclobutane which had high insulation and good planarization characters. Copper coil patterns of 10 μm width and 6 μm thickness were electroplated on Ti (300 A)/Cu (1,500 A) seed layers. 3 μm thick Ni0.8Fe0.2 (permalloy) film for the magnetic core was also electroplated under 2,000 gauss. Excellent linear response over the range of −100 μT to +100 μT was obtained with the sensitivity of ∼280 V/T. Actual chip size was 3.1×3.1 mm2. The sine and cosine signals of two-axis fluxgate sensor had a good function of azimuth compass.