[15p-C302-1~18] 15.6 Group IV Compound Semiconductors (SiC)

△ [15p-C302-3] High Selectivity in SiC/SiO₂ Etching by ICP-RIE in a SF₆-O₂-Ar Chemistry

〇Kana Hiramatsu¹, Takafumi Okuda¹, Jun Suda¹, Tsunenobu Kimoto¹ (1.Kyoto Univ.)

Keywords:etching, SiC, RIE

Reactive ion etching (RIE) is a key process in fabrication of trench MOSFETs, super-junction structure, and MEMS devices. RIE of SiC is relatively easy in spite of its high chemical inertness. However, the etching selectivity against a mask material has been an obstacle for deep etching of SiC. Although high selectivities over 10 can be easily obtained when a metal mask (Al, Ni, etc.) is employed, the usage of a metal mask is not desirable in industrial device fabrication because of metallic contamination and micromasking problem. So far SiO₂ has mainly been used as an etching mask, and the etching selectivity of SiC/SiO₂ is much lower (typically 0.8–4) than that of Si/SiO₂. Furthermore, deep etching of SiC while keeping surface flatness and suppressing “subtrench” near the edge of trench bottom is a challenge. In this study, SiC/SiO₂ etching selectivity in inductively-coupled plasma (ICP)-RIE was investigated. A high selectivity over 8 and a high etching rate of 0.8 mm/min were simultaneously obtained. Using this technique, 16-mm-deep trenches without subtrench could be successfully formed while keeping a smooth surface on the trench bottom.