(Invited) Expanding the Toolbox of Atomic Scale Processing: From Materials Control to Selective Processing By Plasma ALD

Abstract

As we enter an era of atomic scale devices,1 there is a strict need for precise control over the thickness and properties of materials employed in device fabrication.2,3 Furthermore, next-generation device architectures consist of various material layers with dielectric or conductive properties on planar and three-dimensional (3D) features. This has led to an additional need for expanding the toolbox of atomic scale processing techniques – such as atomic layer deposition (ALD) and atomic layer etching (ALE) – with new approaches in selective processing.2,3,4 As early as 1990, different categories of selectivity during film growth on a patterned planar substrate (composed of different surface materials) have been defined in the literature in terms of area-, phase-, microstructure or chemical composition-selective deposition.5 The last three categories have been defined based on the inherent differences in material properties ensuing from simultaneous growth on a patterned substrate. As a result, these cases are simply different examples of one common selective growth process, namely material property-selective deposition. Plasma-enhanced atomic layer deposition (ALD) is a technique that uses the reactive species generated in a plasma (i.e. radicals, ions) for growing materials with atomic scale precision. In this work, we will demonstrate how plasma ALD can open new avenues for controlling material properties and carrying out selective processing on both planar and 3D substrates. We will show how plasma ALD can yield simultaneous growth of the same material with different properties (e.g. phase-selective deposition) on a patterned substrate. We will then demonstrate how implementing ion energy control during plasma ALD can enhance the versatility of this processing technique by enabling accurate control over a wide range of material properties during deposition.6,7 And finally, we will show how controlling ion energies during plasma ALD on 3D trench-shaped nanostructures can provide an alternate route for topographically selective materials processing,6 relevant for next-generation device fabrication.3,4 1 Salahuddin et al., Nat. Electron. 1, 442-450 (2018) 2 Knoops et al., J. Vac. Sci. Technol. A 37, 030902 (2019) 3 Faraz et al., ECS J. Solid State Sci. Technol. 4, N5023-N5032 (2015) 4 Clark et al., APL Mater. 6, 058203 (2018) 5 Carlsson, Crit. Rev. Solid State Mater. Sci. 16, 161-212 (1990) 6 Faraz et al., ACS Appl. Mater. Interfaces 10, 13158-13180 (2018) 7 Faraz et al., Plasma Sources Sci. Technol. 28, 024002 (2019) Figure 1