Glow discharge sputtering has been used for many years to produce
thin films but its commercial applications are severely limited by low
deposit ion rates. The DC planar magnetron, developed a decade ago,
allows much higher deposition rates and its commercial use has expanded
rapidly. Non-reactive magnetron sputtering of metallic thin films is
well understood and utilized. However when a reactive gas is
introduced the process becomes harder to control and can switch between
two stable modes. Often films are produced simply by using one of
these stable modes even though this does not lead to optimum film
properties or high deposition rates.
This work gives a model of reactive magnetron sputtering and
verifies experimentally its predictions. A 0.5 m long magnetron was
designed and built specifically to allow reactive sputtering onto A4
rigid substrates. This magnetron has a variable magnetic field
distribution which allows plasma bombardment of the substrate during
film growth. This was shown to activate reactions at the substrate.
The target lifetime was extended in our design by broadening the
erosion zone and increasing the target thickness. The reactive
sputtering process was shown to be inherently unstable and a control system was designed to maintain the magnetron in an unstable state. Light
emission by the plasma at metal line emission wavelengths changes
across the instability and so with this control signal a feedback
system was built.
The accuracy of control was shown experimentally and
theoretically to depend on the delay time between measurement, action
and effect. In practice this delay was limited by the time constant of
the gas distribution manifold. The time constant of such manifolds was
measured and calculated. Using our controller high quality films were
produced at high rates in normally unstable deposition systems.
Conducting indium oxide was produced at 6 nm/s with a resistivity of 6
x 10-6 ohm. metres onto A4 glass sheets. Tin oxide was produced at
increased rates onto 2.5 m by 3 m substrates.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.