Characterization of MgZnO Thin Film for 1 GHz MMIC Applications

Abstract

MgZnO thin films are proposed as a new dielectric material for 1 GHz monolithic microwave integrated circuit (MMIC) applications. The high permittivity of this material enables size reduction; furthermore this can be fabricated using a low cost processing method. In this work, MgZnO/Pt/Si thin films were synthesized using a sol-gel spin coating method. The samples were annealed at various temperatures with the effects on physical and electrical properties investigated at direct current (DC) and high frequencies. The physical properties of MgZnO thin film were analyzed using X-Ray diffraction, with the improvements shown in crystalline structure and grain size with increasing temperature up to 700 °C. DC resistivity of 77 Ωcm at higher annealing temperature obtained using a four point probe station. In order to prove the feasibility at high frequencies, a test structure consisting of a 50 Ω transmission line and capacitors with 50 × 50 μm electrode area were patterned on the films using electron beam lithography. The radio frequency (RF) properties were measured using aWiltron 37269Avector network analyzer andCascade Microtechon-wafer probes measured over a frequency range of 0.5 to 3 GHz. The dielectric constant, loss tangent and return loss, S11improve with the increment annealing temperature. The dielectric constant was found to be 18.8, with loss tangent of 0.02 at 1 GHz. These give a corresponding size reduction of ten times compared to conventional dielectrics, silicon nitride (Si3N4). These indicate that the material is suitable to be implemented as a new dielectric material for 1GHz MMIC applications.