Growth and characterization of thin SiN films grown on Si by electron cyclotron resonance nitrogen plasma treatment

Abstract

Thin silicon nitride films have been fabricated on Si at a low substrate temperature (about 450 °C) by means of the direct exposure of Si wafers to an electron cyclotron resonance nitrogen plasma generated at 2.45 GHz. The film thickness can be controlled in the range 40–400 Å by suitably changing the nitrogen pressure, microwave power and substrate bias voltage. The activation energy characteristic of the growth is 0.42 ± 0.11 eV. The refractive indices of the films are 1.9–2.0 and the N-to-Si atomic ratio obtained by Rutherford backscattering spectrometry ranged from 1.35 to 1.43, indicating a nitrogen-rich film (stoichiometric value of 1.33). The average breakdown voltage of AlSiNSi capacitors is 11.9 ± 0.2 MV cm −1 and a typical leakage current density is about 10 −9 A cm −2 at a 2 V positive bias stressing for films 16 nm thick. Ion channelling experiments show that silicon nitride films form sharper interfaces (about 5 Å) on the Si substrate than chemically vapour-deposited nitrides do. Optical emission spectra measured during the film growth indicate that the nitrogen molecular ions are closely related to the growth rate and film quality.