(Invited) Control of Atomic Layer Reactions in Plasma Processing

Abstract

Self-limiting chemistries in plasma processes offer a pathway to addressing many process trade-offs associated with profile, selectivity, film quality/surface sub-surface damage and uniformity. Self-limiting plasma processes for etch and deposition are referred to as atomic layer processes for their promise of modification of surfaces with atomic layer precision. The efficacy of atomic layer processes depends in large part on the precursor specie-substrate material pairing that forms reactive layers on surfaces. The reactive layer is to be volatilized in a subsequent step the case of atomic layer etching and primed for further reactions in atomic layer deposition. As much as the precursor itself (e.g., chlorine radicals), the surface condition itself plays a considerable role in the ability of a chemical change to take place on the surface. The surface condition represents itself in limiting the coverage or even in slowing the start of a process. This slowing is well known in atomic layer deposition as incubation time. In plasma processes that seek processing with atomic precision, how the surface can be described in complicated by the presence of ions which may introduce defects on or below the surface depending on their energy and nature or drive chemical reactions. Results from fundamental atomistic simulation techniques are used to show how the details of the surface state (i.e., crystalline, amorphous, terminated in different ways) impact process. Halogen coverage in silicon etch will be used as a backdrop for illustrating surface conditioning effects on more involved processes such as those on nitride or oxide surfaces. Finally, we will illustrate how the solid state chemistry of the sub-surface can impact electrical functionalization of semiconductor devices. We will show how simulation results (macroscale to atomistic) work hand-in-hand to with experiment to demonstrate processes benefiting from self-limitation.