Etch damage evaluation of low-angle, forward-reflected neutral beam etching

Abstract

In the fabrication of nano-scale silicon-based devices, any process-related damage such as electrical charging and surface modification remaining during the processing may cause serious problems due to the size limitation of the devices. Therefore, etching processes with no or negligible damage are required. In this study, an energetic reactive neutral beam of SF6 was formed using a low-angle, forward-reflected neutral beam technique and the etch properties of SiO2 and possible neutral beam-induced damage were investigated. The result showed that, when the neutral beam was formed by the low-angle reflection of the reactive ions generated by the ion gun, most of the reactive ions were neutralized after the reflection at the reflector. When SiO2 was etched with the energetic reactive neutral beams of SF6, the increase of acceleration voltage and SF6 gas flow rates applied to the ion gun increased the SiO2 etch rate possibly due to the increase of energy and flux of the neutrals at the reflector, respectively. Using the neutral beam, a SiO2 etch rate higher than 22 nm/min could be obtained. Also, when etch damage was estimated by measuring the breakdown voltage of SiO2 after the exposure to the oxygen neutral beam, no noticeable damage of SiO2 could be observed.