Abstract
This work summarizes the results of our previous studies related to investigations of reactive ion etching kinetics and mechanisms for widely used silicon-based materials (SiC, SiO2, and SixNy) as well as for the silicon itself in multi-component fluorocarbon gas mixtures. The main subjects were the three-component systems composed either by one fluorocarbon component (CF4, C4F8, CHF3) with Ar and O2 or by two fluorocarbon components with one additive gas. The investigation scheme included plasma diagnostics by Langmuir probes and model-based analysis of plasma chemistry and heterogeneous reaction kinetics. The combination of these methods allowed one (a) to figure out key processes which determine the steady-state plasma parameters and densities of active species; (b) to understand relationships between processing conditions and basic heterogeneous process kinetics; (c) to analyze etching mechanisms in terms of process-condition-dependent effective reaction probability and etching yield; and (d) to suggest the set gas-phase-related parameters (fluxes and flux-to-flux ratios) to control the thickness of the fluorocarbon polymer film and the change in the etching/polymerization balance. It was shown that non-monotonic etching rates as functions of gas mixing ratios may result from monotonic but opposite changes in F atoms flux and effective reaction probability. The latter depends either on the fluorocarbon film thickness (in high-polymerizing and oxygen-less gas systems) or on heterogeneous processes with a participation of O atoms (in oxygen-containing plasmas). It was suggested that an increase in O2 fraction in a feed gas may suppress the effective reaction probability through decreasing amounts of free adsorption sites and oxidation of surface atoms.
Highlights
In our days, silicon-based electronics still keep the dominant position in the worldwide production of various integrated circuits and discrete electronic devices
Silicon dioxide and silicon nitride are a couple of widely used dielectric materials that appear as functional layers in various device structures, spacer dielectrics, passivating coatings and hard masks with high stability in respect to aggressive etchant environments [4,5]
Experiments were carried out in a planar inductively coupled plasma (ICP) reactor (Figure 1), the same as that used in our previous works [36,37,38]
Summary
Silicon-based electronics still keep the dominant position in the worldwide production of various integrated circuits and discrete electronic devices. The component mixing ratio always played the role of the main variable parameter, and the most attention was paid to the following issues: To understand how the chemical nature of the fluorocarbon component and corresponding z/x value influences electron- and ion-related plasma parameters (electron temperature, plasma density, ion flux and energy) that determine both electron impact kinetics and ion–surface interaction efficiency; To figure out differences in steady-state densities of F atoms and polymerizing radicals under the same processing conditions in light of their formation/decay kinetics as well as to evaluate the ability of additive gases (rather, the impact of their mixing ratios) to adjust gas-phase compositions in corresponding gas systems; To compare RIE performances for both non-oxygenated and oxygenated gas systems with respect to various silicon-based materials in terms of etching rates and etching selectivity as well as to suggest corresponding etching mechanisms and limiting stages through correlations between fluxes of active species and obtained etching kinetics
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