Modeling the Dynamics of the Integral Dielectric Permittivity of a Porous Low-K Organosilicate Film during the Dry Etching of a Photoresist in O2 Plasma

Abstract

Using an imitational cellular-automaton model, the structural degradation of a interlayer low-K dielectric during the plasma etching etching of a photoresist is studied. The dielectric represents a porous material based on SiOCH, whose integral dielectric permittivity depends on the percentage of carbon atoms on the pore walls and in the dielectric matrix. The period of etching is such that the removal of carbon (and, accordingly, degradation) is incomplete. The simulation is performed for 2 million steps of the automaton, which correspond to 2 s in the real process. During this period, the number of methyl groups does not exceed 20% of the initial value at the dielectric pore depth of 40 nm; in this case, the permittivity ε increases from 2.5 to 2.84. Extrapolating to a longer time period (nearly 1 min) shows that the total fraction of СН₃-groups is 9% of the initial value through the full depth of the material, while the final value of dielectric permittivity would correspond to 3.0–3.1. The results of the modeling agree with the experimental data described in the literature.