Synthesis and AES analysis of Nb(NbN)–AlN multilayers by off-axial DC magnetron sputtering

Synthesis of a multilayer structure made of superconducting thin films and normal metal or dielectric thin films is an important technology in the superconducting electronics. For example, an S–N–S Josephson junction as a superconducting quantum well device, a superconducting microstrip line and a Josephson transmission line are promising in the future. In this paper, we report on in situ growth of superconductor–dielectric multilayers such as Nb–AlN and NbN–AlN on Si substrate using the off-axial DC magnetron sputtering apparatus and their structural analysis by the Auger electron spectroscopy. We found that Nb, Al and N 2 diffused each other at arbitrary substrate temperatures in the Nb–AlN system. On the other hand, in the NbN–AlN system, Nb and Al slightly diffused when the substrate temperature was low (room temperature), while Nb and Al highly diffused each other when the substrate temperature was high (400°C). NbN–AlN multilayers grown at low substrate temperature were found to be promising in the application such as a superconducting microstrip line. It was also found by the resistivity measurement of AlN thin films that their resistivities were dependent on the input power and partial pressure of N 2 gas during sputtering.