Silicon oxide films have been formed by a RF bias sputter-deposition system using a quartz target in Ar or Ar/O₂ sputtering gas. Substrate bias voltage V_b was varied from 0 to-200 V, at the total power of 1.9 W/cm².
In order to evaluate the planarization effect, the step coverage of the film on AlSi patterns was examined by SEM and compared with the computer simulated profiles using the Lehmann's method, and a good agreement was obtained. Further, we have applied this planarization technology to a 6-level metallization and realized the good step coverage.
The properties of the silicon-oxide films were also studied. In the case of the Ar gas sputtering, the leakage current and the compressive stress in the film increase with increasing V_b. It is found that the Ar/O₂ gas sputtering improves the film properties of both the inner stress and leakage current. Auger analysis indicates that the films deposited in Ar/O₂ gas have O/Si ratio of about 2, but O/Si ratio of the films deposited in Ar gas is less than 2. From these data, the improvement of the properties of the films can be explained as following; oxygen in Si-O network in the films is removed by Ar ion bombardment during bias sputtering, and damaged bond is compensated by oxygen addition.

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Effects of a sputter-cleaning of Nb base electrode on the Josephson junction characteristics have been investigated. Two types of junctions were prepared : One was with thermally oxidized Nb₂O₅ barrier and the other was with Si barrier. A comparison of the junction characteristics with each other revealed that dramatic degradations due to the sputter-cleaning were brought about only to the junction employing a Nb₂O₅ barrier, where the increased sputter-cleaning power resulted in the increased tunnel resistance by several orders of magnitude and the decreased gap parameter of Nb base electrode. An enhanced oxygen diffusion through the plasma bombarded Nb surface layer reasonably explained the observed junction degradation.

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