A Method to Form Bonded Micromagnets Embedded in Silicon

In this work, samarium cobalt (SmCo) powder is utilized for the fabrication of micromagnetic structures embedded in silicon wafers. The fabrication process involves the dry packing of raw, magnetic powder (mean particle diameter of 5-10 mum) into etched cavities within the wafer. After the wafer is loaded with the powder, a 6 mum layer of polyimide is spun over the wafer´s surface to seal the magnetic powder in place and permit the development of additional structures around the embedded magnets. The feature sizes achieved during the investigation range in thickness from 15 mum to the entire depth of the wafer (~ 500 mum), and in lateral dimensions from 150 mum to 600 mum. One set of processed micromagnets demonstrated a coercivity, H_c = 141 kA/m (1.8 kOe), remanence, B_r = 0.52 T (5.2 kG), and maximum energy product, (BH)_max = 23 kJ/m³ (2.9 MGOe).