INFLUENCE OF THE SURFACE ELECTRON PROCESSES ON THE KINETICS OF SILICON ETCHING BY FLUORINE-ATOMS

The model of silicon etching by fluorine atoms is presented. It is shown that the dielectric SiFx film formed on the surface plays an important part in the etching. As a consequence of high heat of adsorption for fluorine atoms on this film its penetration under the surface by thermal activation is difficult. A specific mechanism explaining the origin of the electric field in the film is proposed. The process of electric field formation is connected with valence electrons tunneling from silicon to adsorbed fluorine. The analysis of the electron processes in the SiSiFxF system results in non-linear equations which can be used to calculate the electric field strength and etch rate in a stationary regime. In the proposed model non-activated fluorine penetration into the SiFx film is provided and essential experimental results can be explained. © 1990.