PNNL-13501 - Pacific Northwest National Laboratory

specialized process control sensors, methods, and
algorithms. Process control sensors consist of a positionscannable
Langmuir probe, multi-point optical plasma
emission monitor, residual gas analysis mass
spectrometer, and standard pressure, temperature, and
quartz micro-balance sensors. These sensors measure, as
a function of the position within the mixed oxygen-metal
plasma, the relative concentrations of neutral and ionized
atomic and molecular species, electron concentration and
temperature substrate temperature, and absolute flux
impingement rate per unit area onto the substrate. The in
situ process monitoring and control strategy follows a
method previously reduced to practice that permits
calculation of film composition, from the plasma
discharge characteristics alone, for reactively sputtered
metal-oxides for compositions ranging all the way from
pure metal to stoichiometric oxide (Affinito and Parsons
1984).
Eventually, the methods and results of this research
should prove applicable to all transparent conductive
oxide materials. Developing solar cell, solar-thermal
control film and flat panel display applications are
specific DOE program needs.
Results and Accomplishments
Since all of the transparent conductive oxide materials
involve oxides of low melting point metals, this work
focused on the most well-known transparent conductive
oxide material, namely indium oxide and indium tin
oxide. Preliminary studies were conducted on a
generalized, hybrid, plasma processing method applicable
to the deposition of In2O3 (indium oxide), SnO2 (tin
oxide), and ZnO (zinc oxide) transparent conductive
oxide single-layer and multilayer thin films and films of
these materials with various other dopant atoms added
(like In2O3[SnO2] and In2O3[ZnO]). Particular emphasis
was placed on films of In2O3(SnO2), known as indium tin
oxide, since indium tin oxide is the most commonly used
transparent conductive oxide material. Indium tin oxide
is also the most thoroughly studied, and well understood,
of the transparent conductive oxide materials. The
process for ZnO was also studied, since it is the
transparent conductive oxide of choice for application as a
transparent electrode in solar cells. Since the conduction
mechanisms, and related optical properties are similar for
all of the transparent conductive oxide materials, the bulk
of the experimental studies focused on In2O3 and indium
tin oxide.
Vapor pressure-temperature calculations, which were
proved accurate for thermal deposition of lithium films at
the Laboratory, indicated that the to-be-developed thermal
sources should produce 1000 Å thick transparent
conductive oxide thin films at rates approximately 135
times as high as do the traditional transparent conductive
oxide vacuum deposition techniques that employ
conventional reactive sputtering.
This work was terminated early in the year when the
principal investigator left the Laboratory to pursue other
career opportunities.
Reference
Affinito JD and RR Parsons. 1984. “Mechanisms of
voltage-controlled, reactive, planar magnetron sputtering
of Al in Ar/N2 and Ar/O2 atmospheres.” J. Vac. Sci.
Technol., A,2:1275-1284.
Materials Science and Technology 321