Particle Modeling of Inductively Coupled Plasma and Radicals Flow to Predict Etch Rate of Silicon

Abstract

Plasma and flow in an inductively coupled plasma reactor are examined using particle modeling. Electron collisions are simulated using the Monte Carlo method and hence the spatial distributions of plasma parameters and the production rate of Cl are obtained. The effect of gas pressure on the structure of plasma is examined for the gas pressures ranging from 0.5 to 2.0 Pa. The electron density increases with decreasing gas pressure in the case of chlorine discharge. Cl atoms are produced by dissociation or dissociative attachment; the dissociation is the dominant process. The rate of dissociation is high in the region of skin depth near the coil antenna. Flows of Cl2, Cl, and SiCl4 are examined using the direct simulation Monte Carlo method, where the production rate of Cl is the input data. The spatial distributions of density, temperature, and flow velocity are obtained, together with the radial distribution of the etch rate. The etch product SiCl4 is assumed to be produced by 4Cl + Si →SiCl4 with reaction probability Pr. The etch rate distribution is obtained for values of Pr ranging from 0.1 to 1. The simulated etch rate agrees with the measured etch rate at Pr = 0.16.