Gigahertz Sandwich Strip Inductors Based on Fe-N Films: The Effect of Flux Closure at the Flange

Planar strip inductors consisting of soft Fe-N films enclosing a conductor made of Cu are fabricated on Si substrates and exhibit 70 to 100% inductance gain at 1 Ghz with quality factors of 3 to 5. The magnetic part of the inductance is less than predicted theoretically, which is attributed to hardening of the magnetic material at the edges of the strip, where the deposition is close to 60° incidence. Test films were fabricated on tilted substrates and found to develop very high anisotropy for deposition angles larger than 30°. Optimizing the flux closure at the strip edges is essential for further improving the performance of sandwich strip inductors.