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

摘要

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 degrees C and microwave power between 65 and 520 W. It exhibits a fractal structure with fractal dimension D-f = 1.45 or fractal-like structures for the films deposited without additional heating. When the substrate temperature is raised above 200 degrees C, the uniform dense structure can be obtained. The frequency dependence of the dielectric constant (epsilon') in the frequency range 5-10(6) Hz for the films deposited below 100 degrees C follows a three fractional power law of (epsilon' - epsilon(infinity)') proportional to omega(nt-l) (i = 1, 2, and 3). The exponents n(i) are n(1) = 0.73-0.93, n(2) = 0.95-0.98, and n(3) = 0.87-0.99 in the frequency range of 5-10(2) Hz, 10(2)-10(4) Hz, and 10(4)-10(6) Hz, respectively. The frequency dependence of epsilon' also follows a single power law of (epsilon'-epsilon(infinity)') proportional to omega(n-1) with n = 0.95-0.82 for the films deposited in the substrate temperature range of 200-400 degrees C. The dielectric property of the single power law is in agreement with thr 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 structureof SiNx films. These are partially in agreement with that of the many-cluster anomalous conduction theory of fractal structure. (C) 1998 American Institute of Physics. S0021-8979(98)01911-2. References: 25