Ferrite plating on GaAs for microwave monolithic integrated circuit

Abstract

Ferrite plating can potentially fabricate a ferrite non-reciprocal component on a microwave monolithick integrated circuit (MMIC); It can make crystalline spinel film in an aqueous solution below 90°C, compatible with the low heat resistance of GaAs devices. To show this, we have electro-plated or electroless-plated Fe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> films on GaAs substrates. The film electroless-plated by "spray-spin-coating" method on a SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> intermediate layer (formed by CVD on GaAs) had a mirror plane and a strong adhesion to the surface, though limited in thickness ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\leq 0.8\mu</tex> m). A microstrip junction circulator has been composed of a NiZn-ferrite (Fe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2.47</inf> Ni <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.28</inf> Zn <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.25</inf> - O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> , Ms=478 emu/cc, Hc=37 Oe) film plated on a glass substrate. A circulator action has been observed at 4.0- 4.4 GHz, though very weak (0.6 dB isolation), because the ferrite film (0.8 μm) was much thinner than the substrate (500 μm). The Fe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> and NiZn-ferrite films were polycrystalline with a columnar structure perpendicular to the surface. The magnetization did not exhibit anisotropy, lying in the plane of the film.