Modeling the plasma chemistry of C2F6 and CHF3 etching of silicon dioxide,with comparisons to etch rate and diagnostic data

A detailed chemical reaction mechanism is reported that describes the CA an d CHF3 plasma etching of silicon dioxide, which is widely used in the fabri cation of microelectronic devices. The gas-phase part of the C2F6 mechanism involves 28 species and 132 reactions, while the surface part involves 2 m aterials, 6 species, and 85 reactions. Rate parameters are generally taken from independent studies in the literature, or estimated from rates measure d for related species. Zero-dimensional simulations using these mechanisms compare well with a large body of etch rate and diagnostic measurements in three different high-density plasma reactors. The diagnostic measurements i nclude electron and negative ion absolute densities, CF, CF2, and SiF densi ties, gas temperatures, and ion current densities. An analysis of the domin ant reaction paths shows the importance of gas-phase electron impact reacti ons and the need to include reactions of the etch-product species. On the s urface, the etching reactions are dominated by ion-assisted processes; spon taneous etching by F atoms is relatively unimportant. (C) 2001 American Vac uum Society.