Plasma enhanced atomic layer etching
The atomic layer etching (ALE) technique was developed to obtain fine control of etching reactions with atomic-layer level precision, by separating the adsorption reaction and the activation reaction into discrete steps. In the ALE process, it is critical to achieve a self-limiting reaction where the reaction stops after the etching of a complete atomic layer. By using the self-limiting reactions of ALE, it is possible to realize fabrication processes beyond the sub 5/7 nm technology node. We explain the fundamental principle of ALE and the effect expected from it. In addition, the various ALE approaches developed for different materials and application processes are outlined. Attention is currently focused on the ALE technique for precise control of the etching reaction on a wafer.