Correlation of PECVD SiOxNy dielectric layer structural properties and Si/SiOxNy/Al capacitors interface electrical properties

Abstract

In this work we produce and characterize SiOxNy films deposited by the plasma enhanced chemical vapor deposition (PECVD) technique at low temperatures from silane (SiH4) nitrous oxide (N2O) and helium (He) as precursor gases at different deposition pressures in order to analyze the effect of this parameter on the films structural properties and on the SiOxNy/Si interface quality. In order to compare the film structural properties with the interface (SiOxNy/Si) quality, MOS capacitors were fabricated using these films as dielectric layer. The structure and composition of the films were investigated by, X-ray absorption near-edge spectroscopy (XANES) at the N-K and O-K edges, Rutherford backscattering spectroscopy (RBS) and Fourier transform infrared spectroscopy (FTIR). The MOS capacitors were characterized by low and high frequency capacitance (C–V) measurements, from where the interface state density (Dit) and the effective charge density (Nss) were extracted. The film deposited at 120mTorr presented the best interface quality (Dit∼4×1010eV−1cm−2) and the higher concentration of N–H bonds. This result indicates that this pressure favors N–H incorporation in oxygen vacancies at Si–O–Si bridges, saturating the Si dangling bonds and consequently minimizing Si/SiOxNy interface defects, showing that it is possible to produce high quality dielectric layer by PECVD technique.