High-Frequency Characteristics of SrTiO3 Thin Films in the mm-Wave Band

High-frequency dielectric characteristics of SrTiO 3 (STO) thin films deposited by an electron cyclotron resonance (ECR) sputter on semiconductor substrates are presented. The measured dielectric constant of the STO thin films is from 20 to 125, depending upon deposition temperature and thin film thickness. This is kept constant at a frequency range up to 50 GHz. Dielectric loss expressed in terms of the Qf product is constant in the mm-wave band and is estimated to be comparable to that of bulk STO. STO thin films are found for the first time to be applicable to microwave monolithic integrated circuits (MMICs) operating in the mm-wave band.