Silicon nitride films deposited from SiH 2Cl 2NH 3 by low pressure chemical vapor deposition: kinetics, thermodynamics, composition and structure

Abstract

The growth of stoichiometric and non-stoichiometric silicon nitride films was studied experimentally on 100 mm silicon wafers by batch depositions from the dichlorosilane (SiH 2Cl 2)-ammonia (NH 3) system in a hot-wall horizontal low pressure chemical vapor deposition (LPCVD) reactor. The growth kinetics were discussed in terms of the Langmuir adsorption isotherm. The kinetic parameters were determined by comparing the experimental data with a one-dimensional simulation model. The decomposition of NH 3 at high temperatures was included in the simulation procedure. When the SiH 2Cl 2:NH 3 ratios were greater than 1.5, a quantity higher than the thermodynamic critical values above which Si-rich nitride films begin to deposit, various SiN x films with x < 4 3 were obtained. The composition of the SiN x films was found to vary along the LPCVD reactor. The film stoichiometry was examined by Rutherford backscattering and ellipsometry measurements. According to kinetic and thermodynamic studies, the pyrolysis of dichlorosilane at elevated temperatures (> 700 °C) is the cause for the deposition of Si-rich nitride films. Furthermore, two types of deposited SiN x films were observed; one type showed a typical film density around 3.70 g cm −3 while the other type exhibited a remarkably lower film density below 3.50 g cm −3.