Nanoscale Pattern Transfer by Etching

Lithography and pattern transfer go hand in hand in most nanofabrication processes. Etching is the most commonly encountered subtractive pattern transfer technology, by which substrate material is removed through a patterned mask opening. In this chapter, etching is categorized by wet and dry processes, as well as chemical and physical processes. The key parameters, i.e., selectivity and anisotropy, are examined for all these processes. Based on the author’s own experience, hints on process control in reactive ion etching (RIE) are given. Particular attention is paid to the deep reactive ion etching (DRIE) using inductively coupled plasma (ICP), including Bosch and cryogenic processes. Critical issues encountered in DRIE are discussed such as loading, trenching, notching, micromasking effects, etc. Other novel etching techniques such as metal assisted chemical etching (MACE) and atomic layer etching (ALE) are also presented. Finally, physical etching by ion milling is described.