Influence of annealing in vacuum and in air on magnetic, crystallographic and morphological properties of thin YIG films

Abstract

The Yttrium Iron Garnet (YIG) is chosen by our laboratory for the integration of passive components in the microwaves domain and for the miniaturization of integrated inductors and transformers. Magnetic and morphological characterizations are essential for the development of these components. To fabricate a micro-inductor of solenoid type, we have deposited on an alumina substrate, by RF sputtering, a thin YIG film between two layers of copper. We have also used the photolithography technique in a clean room to obtain the desired pattern of the coil. The YIG films are amorphous after deposition, the annealing at 740°C for 2 hours is necessary for them to be crystallized and to have magnetic properties. To avoid the deterioration of copper layers, the Classical Thermal Annealing (CTA) was replaced by a Vacuum Thermal Annealing (VTA). Before manufacturing the integrated inductor, it is interesting to do the magnetic, crystallographic and morphological characterizations of YIG films after annealing with both techniques of thermal treatment. To check the quality of the prototype, we have done different characterizations: VSM, Kerr effect, XRD, SEM. The results obtained with VTA were better than of CTA comparing them with bulk YIG properties.