Ion-Beam Etching (Milling)

This chapter describes the process of patterning by ion-beam etching. Also called as milling, Ion-beam etching is the slow erosion of a surface because of the bombardment by a stream of high-energy ions. The process is entirely mechanical, being one of momentum transfer between the impinging ions and the surface atoms by which the latter gain sufficient momentum directed away from the surface to produce a net material loss, also known as sputtering. Ion-beam etching shares many similarities with conventional sputtering. The chapter presents the differences between these processes. In ion-beam etching, the source of the ions is separated from the substrate being etched. The characteristics of ion-beam etching and several other dry-etch techniques for micro fabrication compares the operational characteristics, masking requirements, and expected resolution limit of each technique. Ion milling is seen to be a very high resolution anisotropic etch technique that offers good uniformity and predictable etch rates with minimal contamination. The drawbacks of ion etching are its low etch rate, poor selectivity, and potential for device damage.