PLASMA PARAMETERS AND REACTIVE-ION ETCHING KINETICS OF ZnO IN HYDROGEN BROMIDE: THE INFLUENCE OF INERT CARRIER GAS

This work discusses the influence of inert carrier gases, Ar and He, on both gas-phase plasma characteristics and ZnO etching rate under typical reactive-ion etching conditions in the hydrogen bromide environment. Plasma diagnostics by Langmuir probes and 0-dimensional plasma modeling allowed one to compare how the content of given carrier gas does influence electrons-and ions-related plasma parameters, kinetics and densities of plasma active species. It was found that the transition toward Ar- or He-rich plasmas a) causes the growth of electron temperature (due to lower electron energy losses in collisions with atomic species); b) reduces plasma electronegativity; and c) results in opposite changes in both ion density and ion flux. The last phenomenon is due to opposite changes in total ionization rates determined by sufficient difference in ionization rate coefficients for Ar and He atoms. Important features of HBr + Ar plasma at 0–80% Ar are also the slower-than-linear fall of Br atom density (due to the intensification of electron impact dissociation for both HBr and Br2 molecules) as well as an increase in H atom density (due to decreasing their loss rate in gas-phase reactions). Etching experiments indicated that the ZnO etching rate is mostly contributed by the ion-assisted chemical reaction while the reaction rate decreases faster compare with the Br atom flux. The corresponding decrease in the effective reaction probability may be related to changes in both ion bombardment intensity and hydrogen passivation effect. For citation: Efremov A.M., Smirnov S.A., Betelin V.B., Kwon K.-H. Plasma parameters and reactive-ion etching kinetics of ZnO in hydrogen bromide: the influence of inert carrier gas. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 12. P. 86-95. DOI: 10.6060/ivkkt.20246712.7081.