Control of Plasma Etch Conditions through Pulsed, Cyclic, and QALE Processes for Advanced Node Applications

Abstract

Atomic Layer Etching and Quasi Atomic Layer Etching processes have gained a lot of traction and application throughout the last several years. However, not everything described as ALE is a true atomic layer process in its strict definition. In a general consideration, the approach of reactant control, which is the core concept of ALE, is additionally employed in various other applications that are not QALE, e.g. pulsed or cryogenic etching. We will first discuss the definition of cyclic, pulsed, and ALE processes, highlighting similarities and differences. Subsequently, we will highlight and describe specific use cases for which such processes have been explored and implemented at IBM Research in Albany. Fin patterning is a major example of QALE yielding major improvements in profile and CD control during RIE. Additionally, QALE allowed enhanced selectivity during self-aligned contact etches, crucial to its success. For S/D recess possible benefits are expected in a similar fashion. While many of the applications focus on the FEOL, there are also applications of cyclic processes, or QALE-like, in the BEOL, such as Photoresist protection, CD control, and RIE lag reduction. Cryogenic etching can be employed for CD shrink of contact holes to very small dimensions, as well as high aspect ratio etching of small dimensions.