Atomic layer etching of chrome using ion beams.

In this study, two Cr atomic layer etching (ALE) methods have been applied for the precise control of Cr etching. The first one involves O radical adsorption followed by Cl ion desorption (ALE with chemical ion desorption; chemical anisotropic ALE), and the second one involves Cl/O radical adsorption followed by Ar ion desorption (ALE with physical ion desorption; physical anisotropic ALE). Their effects on Cr etch characteristics were also investigated. For both the ALE methods, saturated Cr etch depth/cycle of 1.1 and 1.5 Å/cycle were obtained for the chemical and physical anisotropic ALE, respectively, while maintaining near-infinite etch selectivities with various Si-based materials like silicon, silicon dioxide, and silicon nitride. The Cr etch depth could be controlled precisely with atomic precision by controlling the etch cycles for both Cr ALE methods in addition to the infinite etch selectivities over Si-based materials. Further, the original surface roughness and chemical composition of Cr surface were maintained after Cr ALE. The ALE technique can be used to precisely control the thickness of materials, including metals such as Cr, without any surface damage.