Microstructure and dielectric properties of silicon nitride films deposited by electron cyclotron resonance plasma chemical vapor deposition

Abstract

The microstructures and dielectric properties of silicon nitride (SiNx) films have been investigated. These films were prepared by permanent magnet electron cyclotron resonance plasma chemical vapor deposition by varying the substrate temperature between 56 and 400 °C and microwave power between 65 and 520 W. It exhibits a fractal structure with fractal dimension Df=1.45 or fractal-like structures for the films deposited without additional heating. When the substrate temperature is raised above 200 °C, the uniform dense structure can be obtained. The frequency dependence of the dielectric constant (ε′) in the frequency range 5–106 Hz for the films deposited below 100 °C follows a three fractional power law of (ε′−ε∞′)∝ωni−l (i=1, 2, and 3). The exponents ni are n1=0.73–0.93, n2=0.95–0.98, and n3=0.87–0.99 in the frequency range of 5–102 Hz, 102–104 Hz, and 104–106 Hz, respectively. The frequency dependence of ε′ also follows a single power law of (ε′−ε∞′)∝ωn−1 with n=0.95–0.82 for the films deposited in the substrate temperature range of 200–400 °C. The dielectric property of the single power law is in agreement with the intrinsic dielectric property of Si3N4 films, which is related to electron hopping conduction. The dielectric property of the fractional power law is considered to relate to the fractal structure of SiNx films. These are partially in agreement with that of the many-cluster anomalous conduction theory of fractal structure.