Challenges of tailoring surface chemistry and plasma/surface interactions to advance atomic layer etching

Abstract

The ability to achieve atomic layer etch precision is reviewed in detail for a variety of material sets and implementation methods. For a cyclic approach most similar to a reverse ALD scheme, the process window to achieve a truly self-limited atomic layer etch (ALE) process is identified and the limitations as a function of controlling the adsorption step, the irradiation energy, and the reaction process are examined. Alternative approaches, namely processes to enable pseudo-ALE precision, are then introduced and results from their application investigated. Most of the recent work in plasma process development can be characterized by three fundamental approaches to atomic layer etching. Lastly, recent developments employing reactant flux control are briefly introduced, which have shown to provide a self-limited process that is able to exhibit high selectivity and pattern fidelity. The key feature of this novel method may be the ability to combine advances from the other atomic layer etch approaches.