PLASMAPOLYMERIZED HEXAMETHYLDISILASANE FOR THE PASSIVATION OF YBA2CU3O7-X DEVICES

Electronic devices based on the high-temperature superconductor YBa2Cu 3O7-x (YBCO) may deteriorate in the operating environment under the in fluence of moisture, atmospheric carbon dioxide and frequent thermal c ycling. To avoid these impairments a passivation layer was developed w hich is deposited by polymerization of the silicon organic compound he xamethyldisilasane (HMDS-N) in a plasma enhanced chemical vapour depos ition (PECVD) process. The 100 nm thin films exhibit excellent passiva tion properties which is confirmed by electrical transport measurement s of passivated 6 mu m wide and 100 nm high YBCO lines and step edge J osephson junctions exposed to humidity and CO2. No degradation in the critical parameters such as the critical current I-C, the normal resis tance R-N and the flux-voltage modulation depth Delta V is observed on step edge dc-SQUIDs owing to the deposition of the passivation layer. Atomic force microscope (AFM) measurements show a smooth morphology o f these layers without pinholes and an excellent coverage of the YBCO even at the edges of lines. Furthermore, the passivation layer can be used as an isolation and scratch protection between SQUIDS and thin-fi lm flux transformers in flip-chip magnetometers.