## 1 Introduction
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \begin{tabular}{c} **Ref. \#** \\ \end{tabular} & \begin{tabular}{c} **Plasma** \\ **Type** \\ \end{tabular} & \begin{tabular}{c} **Etching Gases** \\ \end{tabular} & \
\begin{tabular}{c} **Profile Quality** \\ \end{tabular} &
\begin{tabular}{c} **LiNbO\({}_{3}\)** \\ \end{tabular} \\ \hline
[7] & ICP & C\({}_{4}\)F\({}_{8}\)/He (1:1) & Nearly vertical sidewalls; high surface roughness (because of the high level of & X-cut \\  & & & LiF redeposition) & \\ \hline
[8] & ICP/RIE & Ar & Sidewall angle \(\sim\)70\({}^{\circ}\); significant surface roughness & X-cut \\ \hline
[9] & ICP/RIE & CHF\({}_{3}\)/Ar & \
\begin{tabular}{c} Sidewall angle \(\sim\)75\({}^{\circ}\); relatively smooth \\ surfaces (RMS surface roughness \\ \(<\)2 nm) \\ \end{tabular} &
\begin{tabular}{c} \(Z\)-cut \\ \end{tabular} \\ \hline
[10] & ICP & C\({}_{4}\)F\({}_{8}\)/He & Nearly vertical sidewalls; very high surface roughness & X-cut \\ \hline
[11] & ICP & CHF\({}_{3}\)/Ar & \
\begin{tabular}{c} Perfect aspect ratio; smooth surfaces \\ (RMS surface roughness = 10.262 nm) \\ \end{tabular} &
\begin{tabular}{c} X-cut, \\ PE LiNbO\({}_{3}\) \\ \end{tabular} \\ \hline
[12] & ICP & \begin{tabular}{c} CHF\({}_{3}\)/Ar or \\ SF\({}_{6}\)/Ar \\ \end{tabular} & \
\begin{tabular}{c} Nearly vertical sidewalls; smooth \\ surfaces \\ \end{tabular} &
\begin{tabular}{c} X-cut, \\ PE LiNbO\({}_{3}\) \\ \end{tabular} \\ \hline
[13] & ICP/RIE & SF\({}_{6}\)/Ar & Sidewall angle \(\sim\)90\({}^{\circ}\); smooth surfaces & X-cut \\  & & CHF\({}_{3}\)/Ar &
\begin{tabular}{c} Nearly vertical sidewalls; significant \\ surface roughness \\ \end{tabular} & X-cut \\ \hline
[15] & ICP/RIE & CF\({}_{4}\)/He & \
\begin{tabular}{c} Sidewall angle \(\sim\)75\({}^{\circ}\); smooth surfaces \\ (RMS surface roughness = 10 nm, \\ estimated using SEM observation) \\ \end{tabular} &
\begin{tabular}{c} X-cut, \\ PE LiNbO\({}_{3}\) \\ \end{tabular} \\ \hline
[16] & ICP/RIE & SF\({}_{6}\)/Ar & Relatively high surface roughness & Y-cut \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Advances in the dry plasma etching of LiNbO\({}_{3}\). erties of materials [18; 19] that adversely impact the performance parameters of basic integrated optical building blocks and PICs. The aim of this research was to determine the process parameters of reactive ion etching of initial (without a near-surface PE layer) LiNbO\({}_{3}\) in a mixture of SF\({}_{6}\)/Ar gases for developing the technological process of forming integrated optical waveguides with the required aspect ratio and minimal roughness of sidewalls and material surface in the near-waveguide region. Dry plasma etching of LiNbO\({}_{3}\) is quite a challenge. The process is complicated by the formation of the non-volatile compound LiF on the substrate surface during the treatment in fluorine-containing plasma. The formation of LiF on the surface results in a significant decrease in the etching rate, a reduction in the aspect ratio of microstructures and an increase in the surface roughness [20]. [PERSON] et al. [21; 22] demonstrated that the structure of LiF that forms during the process depends on plasma-forming gas mixture: it has an amorphous structure in CHF\({}_{3}\) plasma and is crystalline in CF\({}_{4}\) plasma. Some of the researchers consider the formation of LiF on the surface of LiNbO\({}_{3}\) as a redeposition process without explaining its kinetics [7; 13; 14]. In [23], as well as in several related papers, [PERSON] et al. presented an experimentally confirmed model that explains the kinetics of the etching process of LiNbO\({}_{3}\) in a fluorine-containing plasma. This model was based on the concept of topochemical reactions and describes the stages of LiF-film formation in the case of radical etching of LiNbO\({}_{3}\) with a dominating chemical plasma component.