Model-based analysis of the ZrO2 etching mechanism in inductively coupled BCl3/Ar and BCl3/CHF3/Ar Plasmas

Abstract

The etching mechanism of ZrO2 thin films and etch selectivity over some materials in both BCl3/Ar and BCl3/CBY3/Ar plasmas are investigated using a combination of experimental and modeling methods. To obtain the data on plasma composition and fluxes of active species, global (0-dimensional) plasma models are developed with Langmuir probe diagnostics data. In BCl3/Ar plasma, changes in gas mixing ratio result in non-linear changes of both densities and fluxes for Cl, BCl2, and BCl2+. In this work, it is shown that the non-monotonic behavior of the ZrO2 etch rate as a function of the BCl3/Ar mixing ratio could be related to the ion-assisted etch mechanism and the ion-flux-limited etch regime. The addition of up to 33% CHF3 to the BCl3-rich BCl3/Ar plasma does not influence the ZrO2 etch rate, but it non-monotonically changes the etch rates of both Si and SiO2. The last effect can probably be associated with the corresponding behavior of the F atom density.