Fluorine-doped SiO2 and CF low-k dielectrics obtained during RIE process in fluorine plasmas

We have investigated the effect of silicon dioxide reactive ion etching (RIE) parameters and the type of plasma on the concentration of fluorine and its chemical compounds, such as CF, SiF and SiOF, in the polymer layer that is formed during this process on the top of etched layer, and their thermal stability.The polymeric layer formed on the etched surface appeared to consist of fluorine and silicon fluoride (CF, SiOF and SiF). The thickness and chemical composition of polymer layer formed on the etched surface depends on the type of used fluorine plasma (CF4 or CHF3). Low-k layer formed during RIE in CHF3 plasma consists of CF, SiOF and SiF species, whose intensity and thickness depend on the etching process parameters. For CF4 plasma, polymer layer consists of SiOF and SiF species, whose intensity and thickness depend also on the etching process parameters. However, only for CHF3 plasma it is possible to control the etching/deposition process dynamically by the adequate adjusting process parameters.In contrast to the CF/SiOF/SiF layer formed during RIE in CHF3 plasma, the SiOF/SiF ultra-thin layer is not thermally stable and its thickness is too low for the intermetal dielectric (IMD) application.