Plasma etching of SiO2 using remote-type pin-to-plate dielectric barrier discharge

Abstract

Atmospheric pressure plasma etching of SiO2 was examined using a modified remote-type dielectric barrier discharge (DBD), called “pin-to-plate DBD.” The effect of adding four gases CF4, C4F8, O2, and Ar to the base gas mixture containing N2 (60 slm) (slm denotes standard liters per minute)/NF3 (600 SCCM) (SCCM denotes cubic centimeter per minute at STP) on the SiO2 etch characteristics was investigated. The results showed that the SiO2 etch rate decreased continuously with increasing C4F8 (200–800 SCCM) addition, whereas the SiO2 etch rate increased with increasing CF4 (1–10 slm) addition up to 7 slm CF4. This increase in the SiO2 etch rate up to 7 slm CF4 was attributed to the effective removal of Si in SiO2 by F atoms through the removal of oxygen in SiO2 by carbon in the CFX in the plasma. However, the decrease in SiO2 etch rate with further increases in CF4 flow rate above 7 slm was attributed to the formation of a thick C–F polymer layer on the SiO2 surface. A SiO2 etch rate of approximately 243 nm/min was obtained with a gas mixture of N2 (60 slm)/NF3 (600 SCCM)/CF4 (7 slm), and an input voltage and operating frequency to the source of 10 kV and 30 kHz, respectively. The addition of 200 SCCM Ar to the above gas mixture increased the SiO2 etch rate to approximately 263 nm/min. This is possibly due to the increased ionization and dissociation of reactive species through penning ionization of Ar.

Nanoscience with non-equilibrium plasmas at atmospheric pressure

“…Ichiki et al [16] manage to etch silicon and quartz with halogens at rates approaching 70 µm s −1 and 200 nm s −1 respectively. Again, it appears that the localized nature of treatment is apt to increase the treatment rates by several orders of magnitude [65,120]. This increase is attributed to a comparable increase in the plasma density relative to plasma sources conventionally employed in micro-fabrication processes [121].…”

“…However, to avoid the non-uniformity caused by the filamentary nature of the discharge, another source was designed to operate in the remote mode [64]. In this case, the power electrode is made of aluminium and machined to have multi-pins with a pyramid shape, as shown in figure 1c (after [65]). Electrodes are coated with 300 µm thick alumina to have the dielectric barrier.…”

Investigation of the Atmospheric Helium Dielectric Barrier Discharge Driven by a Realistic Distorted-Sinusoidal Voltage Power Source

“…etching [4], biological decontamination [5], ozone generation [6], pollution control [7], flat plasma display panels [8] and gas lasers [9], to name a few.…”

High-speed etching of SiO2 using a remote-type pin-to-plate dielectric barrier discharge at atmospheric pressure

“…However, if the gas flow rate is very high, the density of the species decomposed in the remote-type plasma source is decreased due to the decreased residence time of the feed gas in the remote source; therefore, the etch rate is decreased. For the etching of SiO 2 with N 2 /NF 3 gas mixtures in a remote-type plasma system, it is impossible to enhance SiO 2 etching by ion bombardment due to the separation between the plasma source and the substrate [22]. And, in particular, for the atmospheric pressure plasma system, due to the extremely small mean free path, only a reactive fluorine atom delivered to the sample by the gas flow without volume recombination is believed to participate in the etching of SiO 2 by forming SiF x .…”