Formation of low defect density SiOx films for Josephson integrated circuits

SiOx films deposited by evaporation under oxygen atmosphere were investigated to form low defect density insulating layers in Josephson integrated circuits. The defect density is high in SiOx films deposited under an oxygen pressure of less than 1.33×10−3 Pa, but it decreases greatly in films deposited under higher oxygen pressure. This can be explained by the presence or absence of elemental Si in the films. Elemental Si is present in films deposited under low oxygen pressure, but not in films deposited under higher oxygen pressure. The insulating characteristics of a SiOx film deposited under an oxygen pressure of 1.33×10−2 Pa are excellent.