Fifteen Nanometer Resolved Patterns in Selective Area Atomic Layer Deposition—Defectivity Reduction by Monolayer Design

Abstract

Selective area atomic layer deposition (SA-ALD) offers the potential to replace a lithography step and provide a significant advantage to mitigate pattern errors and relax design rules in semiconductor fabrication. One class of materials that shows promise to enable this selective deposition process are self-assembled monolayers (SAMs). In an effort to more completely understand the ability of these materials to function as barriers for ALD processes and their failure mechanism, a series of SAM derivatives were synthesized and their structureproperty relationship explored. These materials incorporate different side group functionalities and were evaluated in the deposition of a sacrificial etch mask. Monolayers with weak supramolecular interactions between components (for example, van der Waals) were found to direct a selective deposition, though they exhibit significant defectivity at and below 100 nm feature sizes. The incorporation of stronger noncovalent supramolecular interacting groups in the monolayer design, such as hydrogen bonding units or pi–pi interactions, did not produce an added benefit over the weaker interacting components. Incorporation of reactive moieties in the monolayer component that enabled the polymerization of an SAM surface, however, provided a more effective barrier, greatly reducing the number and types of defects observed in the selectively deposited ALD film. These reactive monolayers enabled the selective deposition of a film with critical dimensions as low as 15 nm. It was also found that the selectively deposited film functioned as an effective barrier for isotropic etch chemistries, allowing the selective removal of a metal without affecting the surrounding surface. This work enables selective area ALD as a technology through (1) the development of a material that dramatically reduces defectivity and (2) the demonstrated use of the selectively deposited film as an etch mask and its subsequent removal under mild conditions.

Non‐self‐sustained electron beam RF‐generated plasma in application for functional surface pretreatment

“…An additional advantage of ASD is a possibility to grow materials in a bottom‐up fashion for future interconnect technology, which allows filling of narrow/high aspect ratio structures without the formation of voids and seams, which become a stringent problem when sub‐10‐nm CD structures are to be filled with deposition techniques. [ 1–4 ] The preliminary surface pretreatment by low‐energy ions or low‐energy ions with radicals can be used for this goal.…”

Thermal Annealing of Molecular Layer-Deposited Indicone Toward Area-Selective Atomic Layer Deposition

“…Second, another strategy used in AS-ALD is to utilize inhibitors to deactivate film growth, such as self-assembled monolayers (SAMs), polymer films, and carbon materials. First, SAMs are often utilized as surface inhibitors, which often require solution-phase processes and relatively long process time scales of 24–48 h. − Second, polymeric coatings have also been used as inhibitors; however, undesired nucleation may occur via polymer trapping of the precursors, and a polymer substrate is difficult to completely remove post-deposition. , Lastly, carbon-based inhibitors, such as graphene, graphite, and amorphous carbon, are often deposited by solution processes, chemical vapor deposition (CVD), or ion implantation. − However, the application of these methods on high aspect ratio substrates is difficult. Due to these difficulties, it is necessary to develop a novel method that enables conformal inhibition for AS-ALD on 3D substrates.…”

Dense Organosilane Monolayer Resist That Directs Highly Selective Atomic Layer Deposition

“…The surface preparation and cleaning steps in particular produce a uniform starting surface for deposition of the layer and remove defects in the layer after it is formed. Organosilane monolayers deposited on SiO 2 are used as resists and promotors in nanodevice fabrication. − The starting surface is produced by cleaning silicon covered by an oxide with a series of solvents to remove contamination followed by an oxidizing acid, oxygen plasma, microwave radiation in air, or UV light in air to form hydroxyl groups for the organosilane to react with and covalently attach to the SiO 2 surface. ,− After depositing the organosilane, defects such as physically adsorbed molecules are removed from the layer by solvent extraction. The organosilane deposition and solvent extraction steps are repeated to form the final monolayer. ,, The thickness and contact angle of the final monolayer are readily measured but are often not good predictors of performance, in particular, the extent that the monolayer passivates a surface, which complicates comparing different process sequences.…”

“…However, gas phase precursors like those used in ALD may be able to penetrate the monolayer, and strengthening intermolecular interactions could reduce the defect density and create a better diffusion barrier. A study was undertaken to test this idea with an alkylphosphonic acid monolayer . Defects were detected by selective ALD of ZnO on Si relative to Cu.…”