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High rate deposition of alumina films by reactive gas flow sputtering

: Jung, T.; Westphal, A.


Surface and coatings technology 59 (1993), Nr.1-3, S.171-176
ISSN: 0257-8972
International Conference on Plasma Surface Engineering <3, 1992, Garmisch-Partenkirchen>
Zeitschriftenaufsatz, Konferenzbeitrag
Fraunhofer IST ()
alumina film; high rate deposition; hollow cathode; reactive sputtering

A new sputter source which enables higher deposition rates than standard magnetron sputtering, especially for oxide films, has been developed. The deposition process typically works at some tenth of a millibar and requires no high vacuum environment. It's basic principle consists of the sputter erosion of the inner walls of a hollow cathode (here: aluminium) by a dc discharge and the subsequent transport of te sputtered material out of the hollow towards the substrate by the inert working gas (argon) flowing through this hollow. The reactive gas (oxygen) is added outside the hollow and does not react with the target surface, mainly due to the working gas counter-flow. The particular route of the working gas flow also strongly decreases the residual gas influence on the target and the substrate. For practical applications, a linear sutter source of 10 cm length and 2 cm width which allows to coat an area of appr. 50 square centimetre has been tested. Up to now, deposition rates of 10 My mh at 1.4 kW dc power have been realised. Total pressure and gas flow were in the range of 0.4 m bar and 800 sccm, respectively. In spilte of the rather high working pressure and the intense argon gas flow towards the substrate the argon content of the films is verylow (equal or smaller than 0.01 vvt.-%). The concept of the linear hollow cathode with two parallel rectangular targets was found to be simple in construction and operation and can be easily extended in two dimensions for the coating of large areas.