Low<i>k</i>thin films based on rf plasma-polymerized aniline

Abstract

Thermally stable materials with low dielectric constant (k &lt; 3.9)\nare being hotly pursued. They are essential as interlayer dielectrics/intermetal\ndielectrics in integrated circuit technology, which reduces parasitic capacitance\nand decreases the RC time constant. Most of the currently employed materials\nare based on silicon. Low k films based on organic polymers are supposed to\nbe a viable alternative as they are easily processable and can be synthesized\nwith simpler techniques. It is known that the employment of ac/rf plasma\npolymerization yields good quality organic thin films, which are homogenous,\npinhole free and thermally stable. These polymer thin films are potential\ncandidates for fabricating Schottky devices, storage batteries, LEDs, sensors,\nsuper capacitors and for EMI shielding. Recently, great efforts have been made in\nfinding alternative methods to prepare low dielectric constant thin films in place\nof silicon-based materials. Polyaniline thin films were prepared by employing\nan rf plasma polymerization technique. Capacitance, dielectric loss, dielectric\nconstant and ac conductivity were evaluated in the frequency range 100 Hz–\n1 MHz. Capacitance and dielectric loss decrease with increase of frequency and\nincrease with increase of temperature. This type of behaviour was found to be in\ngood agreement with an existing model. The ac conductivity was calculated from\nthe observed dielectric constant and is explained based on the Austin–Mott model\nfor hopping conduction. These films exhibit low dielectric constant values, which\nare stable over a wide range of frequencies and are probable candidates for low k\napplications.