High Aspect Ratio Silicon Nanohole Arrays via Electric-Field-Incorporated Metal-Assisted Chemical Etching

The implementation of through-silicon vias for high-performance semiconductor devices requires a reliable fabrication process that can achieve high aspect ratio (HAR) silicon nanoholes (Si NHs). Currently, Si NHs are primarily fabricated via plasma-based dry etching, which has technical limitations, such as necking and bowing. Metal-assisted chemical etching (MaCE) is an alternative Si NH fabrication method that utilizes wet chemistry catalyzed by metals. However, the formation of HAR Si NHs is challenging because of the unstable motion of metal catalysts during MaCE. Herein, we introduce electric-field-incorporated MaCE (EMaCE) to improve the anisotropic etching stability of metal catalysts and achieve the formation of Si NHs. The etch straightness gradually improved with increasing electric field intensity while the etch rate remained nearly constant. We optimized the etchant concentration and etch time to increase the etch rate, and thus, fabricated an ultra-HAR (38:1) Si NHs array via EMaCE.