Atomic Layer Etching: Rethinking the Art of Etch

Abstract

Atomic layer etching (ALE) is the most advanced etching technique in production today. In this Perspective, we describe ALE in comparison to long-standing conventional etching techniques, relating it to the underlying principles behind the ancient art of etching. Once considered too slow, we show how leveraging plasma has made ALE a thousand times faster than earlier approaches. While Si is the case study ALE material, prospects are better for strongly bound materials such as C, Ta, W, and Ru. Among the ALE advantages discussed, we introduce an ALE benefit with potentially broad application-the ALE smoothing effect-in which the surface flattens. Finally, regarding its well-established counterpart of atomic layer deposition (ALD), we discuss the combination of ALE and ALD in tackling real world challenges at sub-10 nm technology nodes.

Atomic layer etching of SiO2 with Ar and CHF3 plasmas: A self‐limiting process for aspect ratio independent etching

“…Advanced nanomanufacturing is increasingly demanding atomic‐scale process controllability to produce features with sub‐10 nm critical dimensions . The performance of the resultant devices depends critically on the etching step, presenting etch challenges that continue to increase as process requirements grow more stringent .…”

“…Advanced nanomanufacturing is increasingly demanding atomic-scale process controllability to produce features with sub-10 nm critical dimensions. [1,2] The performance of the resultant devices depends critically on the etching step, presenting etch challenges that continue to increase as process requirements grow more stringent. [3,4] The necessary control of surface properties in combination with the decrease in overall film thicknesses require material selectivity and atomic scale control of etching directionality at the truly atomic scale.…”

Anisotropic atomic layer etching of W using fluorine radicals/oxygen ion beam

“…When the formation of WO x was further investigated during the ALE cycles just exposing to the oxygen ion beam ( + 30 V of first grid voltage) during the desorption step without adsorbing F radicals during the adsorption step, as shown in Figure S2, no WO x formation was observed when the W was exposed equal to and <30 s/cycle. Finally, using the adsorption conditions with F radicals (300 W of RF power to the ICP source, 2 mTorr NF 3 Figure 4 and the results are shown in Figure 5. The RMS surface roughness for the as-received reference W was~0.9 nm and, after the adsorption of F radicals for 10 s, the roughness was remaining at~0.91 nm, therefore, no change of surface roughness was observed by the F radical adsorption on W. After the F radical adsorption, when the F-adsorbed W was desorbed by O x + ions for 3 s and 5 s, the surface roughness was increased to 1.21 and 1.29 nm, respectively, due to the partial removal of WF y by O x + ions on the F-adsorbed W surface.…”

“…Recently, atomic layer etching (ALE) technology has attracted much attention due to miniaturization and high integration of semiconductor devices . This ALE technology can process semiconductors more precisely than conventional reactive ion etching (RIE) and has advantages such as high etch selectivity, low surface damage, etc . In general, the ALE studies using plasmas have been investigated by adsorbing reactive gases such as radicals or reactive molecules on the surface for the modification of the surface by chemisorption, and then by removing the modified surface layer only by using energetic ions.…”

“…[1,2] This ALE technology can process semiconductors more precisely than conventional reactive ion etching (RIE) and has advantages such as high etch selectivity, low surface damage, etc. [3][4][5] In general, the ALE studies using plasmas have been investigated by adsorbing reactive gases such as radicals or reactive molecules on the surface for the modification of the surface by chemisorption, and then by removing the modified surface layer only by using energetic ions. Using these techniques, a precise etch depth/cycle of various semiconductor related materials such as Si, III-V compounds, metals, and 2D materials has been achieved.…”