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Abstract:
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Thermally stable materials with low dielectric constant (k < 3.9)
are being hotly pursued. They are essential as interlayer dielectrics/intermetal
dielectrics in integrated circuit technology, which reduces parasitic capacitance
and decreases the RC time constant. Most of the currently employed materials
are based on silicon. Low k films based on organic polymers are supposed to
be a viable alternative as they are easily processable and can be synthesized
with simpler techniques. It is known that the employment of ac/rf plasma
polymerization yields good quality organic thin films, which are homogenous,
pinhole free and thermally stable. These polymer thin films are potential
candidates for fabricating Schottky devices, storage batteries, LEDs, sensors,
super capacitors and for EMI shielding. Recently, great efforts have been made in
finding alternative methods to prepare low dielectric constant thin films in place
of silicon-based materials. Polyaniline thin films were prepared by employing
an rf plasma polymerization technique. Capacitance, dielectric loss, dielectric
constant and ac conductivity were evaluated in the frequency range 100 Hz–
1 MHz. Capacitance and dielectric loss decrease with increase of frequency and
increase with increase of temperature. This type of behaviour was found to be in
good agreement with an existing model. The ac conductivity was calculated from
the observed dielectric constant and is explained based on the Austin–Mott model
for hopping conduction. These films exhibit low dielectric constant values, which
are stable over a wide range of frequencies and are probable candidates for low k
applications. |