A microprocessor-controlled magnetron system for sputtering optical films

Abstract

We report the development of a thin film coating plant with a magnetron source which permits the controlled growth of reactively sputtered metal oxide films for optical purposes. Both high frequency quartz crystal and optical thickness monitors are incorporated in the instrumentation. The former provides a thickness (and rate) indication to a possible precision of better than ±0.01 nm and the latter gives an indication of maxima ir minima in the reflection coefficient to permit deposition termination at thicknesses of multiple quarter-wavelengths. The source target takes the form of a plane disc but sputtering from its surface is restricted by magnetron action to an annular region on the front face. This provides a central aperture in the target through which the chopped light beam passes to impinge normally on the test substrate before analysis by a phase-sensitive detection system. In conclusion an example is given of the controlled growth of a reactively sputtered tin oxide film.