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

Abstract

High‐aspect‐ratio (HAR) etch of SiO2 films was attempted using a low‐frequency (2 MHz) bias power in an inductively coupled plasma (ICP) system using heptafluoroisopropyl pentafluoroethyl ketone (C6F12O) gas, which has a lower global warming potential (GWP). Etching characteristics of the oxide film according to changes such as the CF4/C6F12O mixing ratio, source power (13.56 MHz), and bias power were derived. To understand the etching characteristics and mechanism, optical emission spectroscopy (OES), double Langmuir probe (DLP) measurement, and X‐ray photoelectron spectroscopy (XPS) analysis were performed. We observed the vertically etched profile of the 100 nm etched line pattern with a scanning electron microscope (SEM) and at first suggested that the HAR oxide etching process is feasible using the ICP system.

Necking Reduction at Low Temperature in Aspect Ratio Etching of SiO2 at CF4/H2/Ar Plasma

“…The effect of the change of the plasma property with the temperature on the aspect ratio and the etch rate of SiO 2 was investigated. Thus, the spectral line intensity ratio in Figure 6 was obtained by monitoring the spectral line intensity of species (CF 3 (610.8 nm), CF 2 (340 nm), F (703.8 nm), C 2 (516.5 nm), and H (486.1 nm)) from CF 4 /H 2 /Ar plasma during the aspect ratio etching of SiO 2 using OES [ 11 , 12 , 13 ]. As the spectral line intensity ratio CF/F was excessively low, it is not shown in Figure 6 .…”

Noble gas effect on ACL etching selectivity to SiO2 films

“…Another 2 MHz RF generator (advanced energy, CESAR RF power generator) powered the lower electrode to produce the negative bias voltage, U − dc . [4] The temperature of the lower electrode was maintained at ∼0°C using the built-in isopropyl alcohol flow-cooling system.…”

“…The chemical composition of the plasma-treated ACL material surface was investigated using X-ray photoelectron spectroscopy (XPS; K-Alpha; Thermo VG), as described in a previous study. [4] To examine the plasma characteristics, plasma diagnosis was performed using a double Langmuir probe (DLP) (DLP 2000; Plasmart Inc.) and OES (Avaspec-3648; JinYoung Tech). In DLP experiments, the probe head was located of ∼5 cm above the bottom electrode as well as was centered in the radial direction.…”

“…The main feature of the RIE process is the combination of physical and chemical etching pathways that allows one to control both pattern size and profile shape through fluxes of chemically active neutrals and energetic ions. [2,4] The important task of modern IC technology is the high aspect ratio (HAR) silicon oxide etching with a pattern size of several nanometers. The leading semiconductor device makers, such as Samsung and Hynix, have realized this process using the plateparallel RIE etcher operated with capacitively coupled plasma (CCP).…”

“…Recently, it was reported that the ICP etching system with a 2 MHz bias power can be applied to the HAR oxide etching process. [4] At the same time, the corresponding results represent only the initial stage of the research process and thus, cannot provide a direct solution for HAR technology. The latter means that further study of ICP etching systems connecting a 2 MHz bias power to the lower electrode is required.…”