Optimization of photoresist development and DRIE processes to fabricate high aspect ratio Si structure in 5 nm scale

Abstract

The fabrication of high aspect ratio (AR) Si structure with extremely small feature size is attracting more and more attention recently. In this work, a top-down scheme for fabricating nanostructures with 4.4 nm line width and 40:1 AR has been proposed and demonstrated. This technique utilizes electron beam lithography for nano-scale patterning and deep reactive ion etching (DRIE) for pattern transfer. In this method, a special development strategy is discussed to improve the perpendicularity of the photoresist mask, and a novel nano-scale barrel is utilized as the testing structure for the DRIE process optimization. To study the critical dimension (CD) variation in the DRIE process, the geometric morphology of the obtained vertical barrels is simulated by an ion transport model. It is found that the asymmetrical lateral etching encroachment decreased the CD loss by 50%. Without using a hard mask, this technique is fully compatible with Si-based microelectronic processes. Therefore, after further study of geometric properties of the obtained nano structure, this proposed microelectronic-compatible approach sheds light on manufacturing 3D nano devices towards 5 nm scale and beyond.