| 초록 |
As the critical dimension shrinks in nanoscale, cleaning patterns gets challenging due to high aspect ratio. Typically wet cleaning processes are applied to remove native oxide, but they are reaching the limits in high aspect ratio patterns. Recently new dry-cleaning technology are being studied to overcome the limitations of wet cleaning processes. Many perfluorocarbon such as CHF3, and C4F8 gases are widely used in semiconductor processes for etching and cleaning processes. C3F7OCH3 gas has lower global warming potential (GWP) of 530 than CHF3 (12,400) and C4F8 (8,900). In this work, a cyclic quasi atomic layer etching process was developed for high aspect ratio patterns (5:1) for oxide removal with surface fluorination in an inductively coupled plasma (ICP) reactor. The process consists of two steps. In the first step, SiO2 surface is modified with fluorocarbon polymers generated with C3F7OCH3. In the second step the fluorinated oxide is removed with Ar or O2 plasma. Cleaning rate was investigated by varying bias voltage. Self-limiting removal rate under 10 Å/cycle was confirmed and the removal rate dependence on gases and plasma power was investigated. |
