Anisotropic Etching of Si and WSiN Using ECR Plasma of SF₆–CF₄ Gas Mixture

Abstract

The characteristics of Si etching with electron cyclotron resonance (ECR) plasma of SF6–CF4 are studied in order to improve anisotropy in dry etching using fluoride gases. Si undercutting is decreased by increasing the amount of CF4. Si patterns with vertical sidewalls are obtained with an etch rate of 40 nm/min. Oxygen addition to SF6–CF4 increases Si/SiO2 etching selectivity to more than 10, but does not cause any undercutting. It is concluded that carbon (C) that decomposes from CF4 protects the pattern sidewall from undercutting by fluorine radicals. These results are applied to the anisotropic etching of WSiN as the gate material for GaAs metal-semiconductor field effect transistors (MESFETs). WSiN patterns are more vertical when the chamber inner wall exposed to SF6–CF4 ECR plasma is stainless steel rather than quartz. This is attributed to the reduction of the amount of CO, which possibly forms volatile tungsten-carbonyl [W(CO)6] and, along with fluorine radicals, causes undercutting. It is confirmed that the stainless steel inner wall does not cause serious wafer contamination by metallic elements when WSiN patterns are almost vertically etched.

Accurate Dry Etching with Fluorinated Gas for Two-dimensional Si Photonic Crystal

“…The chlorinated gas was Cl 2 . The fluorinated gas was SF 6 , CF 4 , or a mixture of SF 6 and CF 4 [6]. Ni was patterned as the etching mask by the lift-off method, including electron beam writing and Ni evaporation [7].…”

“…The deposition phenomena of CF 4 ECR plasma are attributed to this plasma generation characteristics. Therefore, SF 6 can etch Si at a high rate, and CF 4 can be used in order to provide the deposition factors (D, E) shown in Fig. 2.…”

Thermal robustness evaluation of nonvolatile memory using Pt nanogaps

“…The SiO 2 layer could be removed with high accuracy using the electron cyclotron resonance plasma of CF 4 . [19][20][21][22] The etching depth of the SiO 2 layer was about 50 nm. During etching, metal layers consisting of nanogap structures functioned as an etching mask.…”

Silicon wire waveguiding system: Fundamental characteristics and applications

“…ECR plasma etching with SF 6 -CF 4 gas mixture can make Si patterns with vertical sidewalls [22]. It can be performed at low gas pressures of 0.1 Pa or less and only the low-energy ions irradiate the wafer.…”