Fabrication of 945 MHz Band Film Surface Acoustic Wave Resonators Using ZnO Thin Film with Si Substrate

This paper, we present the analysis of a ladder-type filter, in the frequency band of 945 MHz, developed on a structure with two layers of a ZnO film on a Silicon substrate with aluminum (AT) IDTs using coupling of modes (COM) theory. The case of a layer ZnO deposited on a not-piezoelectric substrate, [111]-[110]-Si is examined. Although silicon is no piezoelectric, the configuration gives for the modes of surface of a higher order, the coupling coefficients K2 of about 5.5% (quite higher than the maximum value obtained for ZnO alone 1%) with the metallization coefficient of 0.5. We presents the optimization of the characteristics SAW, in particular by the choice of:-the thickness of the piezoelectric layer,-localization of IDTs,-the metallization or not of surface or interface,-crystalline orientation of the substrate and propagation direction, -the thickness of the fingers of IDT. The transfer function of SAW ladder type filter resonators (6 resonators) is presented, analyzed and compared with the experimental results. This frequency response confirms that it is possible to integrate on Si substrate the filters use for GSM and DECT systems.