Comparative study of CF₄ + O₂ and C₆F₁₂O + O₂ plasmas for reactive‐ion etching applications

Abstract

This work represents a comparative study of gas-phase parameters and reactive-ion etching kinetics for Si and Si and SiO 2 in CF 4 + O 2 and C 6 F 12 O + O 2 plasmas. An interest to the C 6 F 12 O gas is because it combines the low global warming potential (low environmental impact) and weakly studied dry etching performance. It was shown that the investigated gas systems showed similar effects of processing conditions on electron-and ion-related plasma parameters as well as on the densities of F and O atoms. Etching experiments showed identical behaviors of Si and SiO 2 etching rates as well as very similar SiO 2 /Si etching selectivities. The notable feature of the C 6 F 12 O + O 2 plasma is only the systematically lower absolute etching rates that correlate with lower in F atom densities.dodecafluorooxepane, global warming potential, heterogeneous reaction kinetics, ion energy and flux, plasma diagnostics, plasma modeling | INTRODUCTIONGases from the fluorocarbon family have an important place in the electronic device production industry, as they are used for dry (reactive-ion) patterning of Si and SiO 2 . [1][2][3] These two materials are widely used in planar integrated structures as either substrates (mostly silicon itself) or various functional layers (mostly silicon dioxide). [2][3][4][5] Recently, the increasing attention paid to both device dimensions and performance has led to the continuous optimization of dry etching techniques toward achieving more anisotropic etching profiles, lower surface damage and residues, and better SiO 2 /Si etching selectivities. Progress in this direction requires a thorough understanding of etching mechanisms, transparent interconnections between gas-phase plasma parameters and surface reaction kinetics, and known features of various fluorocarbon-based plasmas in respect to Si and SiO 2 etching processes.

High‐aspect‐ratio oxide etching using CF4/C6F12O plasma in an inductively coupled plasma etching system with low‐frequency bias power

“…This is consistent with the results from previous studies, which showed that the C 6 F 12 O gas etch rate is lower than the CF 4 gas etch rate. [ 12,13 ] However, as shown in Figure 4, as the mixing ratio of C 6 F 12 O gas increased, the etch rate of the ACL material decreased more than the decrease in the SiO 2 etch rate. Consequently, it was confirmed that the etch selectivity for the ACL material increased as the mixing ratio of C 6 F 12 O gas increased.…”

“…Accordingly, recent research on etching technology using this gas has been conducted. [12,13] In this study, a HAR oxide etching process was performed using an ICP system with a low-frequency bias power system. The etching characteristics were investigated for HAR oxide patterns at 13.56 and 2 MHz bias power.…”