Abstract
Aluminium zinc oxide (AZO) thin films continue to be important in the diversification and development
of transparent conducting oxide (TCO) based products, particularly those aimed at microelectronics for
photovoltaic applications and improvements in their deposition remains critical. This thesis addresses this
requirement. It reports on sputter deposited AZO thin films as a function of rf power deposited using
remote plasma sputtering, and the plasma properties of the downstream remote plasma source under varying
deposition conditions, measured using optical emission spectroscopy (OES).
An optimum rf power exists for the remote plasma sputtering (RPS) of AZO thin films using a ceramic
sputter target, occurring at an intermediate rf power surrounding 1.50 kW for a constant target power of
445 W. The resistivity was 6.35 × 10−4 Ω · cm and visible region optical transmittance 92 %. The coatings
were dense, had a stoichiometric composition and no measurable argon inclusion. Here exists a region of
energy balance that promotes dense, high quality coatings, without any damaging effects from either high
ion energy or high plasma density.
Argon injection at the target produces a plasma with characteristics indicative of a high ne, including
an increasing Tef f and quenched excited atom density. Several measurements of ne showed it lying in the
region of 1012 cm−3. Excited atom densities were found to be generally high 1010 − 1011 cm−3, possibly
explaining some of the beneficial energetic effects on film growth of RPS. Introducing argon gas in varying
ratios between the PLS and target demonstrated the versatility of RPS to operate in different coupling and
flow regimes. Measurements of ne and Tef f with target bias highlighted a growth in the relative density of
ionised sputter atoms with increases in rf power and a sharp rise in ne, nm and nr at powers greater than
700 W. This proves that RPS is an IPVD process, causing significant ionisation of the sputter flux.
The results presented in this thesis highlight the important role the rf power of a remote plasma source
plays in determining the fundamental plasma properties during thin film growth of AZO. This new
information, along with the new collisional regimes highlighted as a function of process pressure
distribution, can be used to widen the AZO sputter process window to find new deposition conditions that
may enhance certain growth regimes, leading to films with high quality and possibly unique properties.