Area‐Selective Atomic Layer Deposition Using Vapor Dosing of Short‐Chain Alkanethiol Inhibitors on Metal/Dielectric Surfaces

Abstract

with modification of surface characteristics, which allows a desired film to be deposited on one region of pre-patterned surfaces (i.e., growth areas) while simultaneously inhibiting deposition in adjacent regions (i.e., non-growth areas). [3,[7][8][9][10] One of the most common strategies for the successful implementation of AS-ALD is to locally deactivate non-growth areas with self-assembled monolayers (SAMs) as inhibitor molecules. [11][12][13][14][15][16][17] In other words, surface modification with such alkylating agents is the most important prerequisite in that the subsequent ALD process operates with a strong dependence of the surface character in the employed substrates by virtue of a surface-reaction-controlled regime with an alternating exposure of precursor and co-reactant molecules. [4][5][6]18] Despite many efforts in successful AS-ALD methods using SAMs, there remain several challenges for practical implementation of selective deposition with SAMs in an industry-compatible process. First, due to a lack of volatility, monolayeric formation of uniform SAMs requires an exceedingly long coating time involving immersion into SAMcontaining solutions for several hours to a few days, depending on the type of SAMs and employed substrates. [13,[19][20][21][22][23][24] In addition, their blocking capability against the subsequent ALD process relies on alkyl chain lengths in the backbone of SAMs, such that using SAMs with alkyl chain lengths greater than 12 units of carbon can provide high enough blockage by virtue of strong van der Waals interaction between adjacent SAMs. [16] However, when it comes to the formation of such bulky SAMs across complex 3D nanostructures with regions of high curvature, the presence of their steric hindrance appears to be a critically limiting factor to confer deposition selectivity, indicative of incompatibility with advanced 3D nanofabrication. [25] To overcome the above-indicated limitations, many attempts have been made to enable facile and efficient surface modification through vapor-phase functionalization of small inhibitor molecules on non-growth areas. [1,4,7,17,26] Among them, surface alteration with vapor dosing of such short-chain aminosilanes showed promise toward rendering much smaller surface alkylating agents with short exposure times, making it more suitable for integration of AS-ALD in the complex and 3D nanostructures. However, their blocking ability was found to be limited to very thin films in comparison with long-chain SAMs due to the relatively limited van der Waals interactions between short alkyl Area-selective atomic layer deposition (AS-ALD) has enormous potential for selective formation of thin films in a bottom-up additive fashion on predefined areas. Despite significant efforts in a number of AS-ALD processes using bulky self-assembled monolayers (SAMs) with long alkyl chains as inhibitor molecules on non-growth areas, there is increasing interest in achieving selective deposition compatible with complex 3D structures with smaller technology nodes in...

Area-Selective Atomic Layer Deposition on Metal/Dielectric Patterns: Amphiphobic Coating, Vaporizable Inhibitors, and Regenerative Processing

“…After SAM treatment, the water contact angles of the DT-treated Co surfaces are measured to be 100°± 4°, consistent with the previous report for the alkyl-thiol SAMs on Cu substrates. 14,24 The water contact angles of the FDT-treated Co surfaces are measured to be 140°± 6°for both vapor and solution depositions, showing the significant water-repellent ability of the fluoroalkyl group. 29,30 Simultaneously, the water contact angles on the SiO 2 surfaces are measured to be 36°± 2°, keeping similar hydrophobicity before and after the SAM treatment of DT and FDT, caused by the low reactivity of alkyl-thiol to the SiO 2 substrate.…”

“…For example, silane SAMs have been used to modify SiO 2 substrates to block the deposition of HfO 2 , Pt, ZnO, and Al 2 O 3 . − In addition to the modifications of dielectric substrates, phosphoric acid SAMs have been widely used to modify the metal substrates such as Cu, Co, W, and Ru to block the deposition of Pt, ZnO, and Al 2 O 3. ,,, Moreover, thiol SAMs have drawn significant attention in AS-ALD of Al 2 O 3 and ZnO on Cu substrates because of their much shorter deposition times and vaporizable processes, providing more compatibility for industrial applications. ,, The AS-ALD using SAM modifications, however, have been mainly investigated on conventional copper-based interconnects. SAM modifications on other interconnect metals, such as Co, Ru, and Mo substrates, have not yet to be well investigated to achieve the AS-ALD.…”

“…10, 12,13,22 Moreover, thiol SAMs have drawn significant attention in AS-ALD of Al 2 O 3 and ZnO on Cu substrates because of their much shorter deposition times and vaporizable processes, providing more compatibility for industrial applications. 14,23,24 The AS-ALD using SAM modifications, however, have been mainly investigated on conventional copper-based intercon- Recently, the surface modification of fluorocarbons (CF x ) has been considered a good blocking layer because of the significant hydrophobicity and retardation of nucleation during the ALD process. 25,26 In previous work, we also performed the AS-ALD of Al 2 O 3 on the Co substrates using fluorinated SAMs, showing significant blocking ability and higher selectivity compared with conventional SAMs with long-alkyl chain molecules.…”

The Effect of Surface Terminations on the Initial Stages of TiO2 Deposition on Functionalized Silicon

“…For microelectronic applications, selectivity between pre-patterned growth-promoting regions of the surface growth substrates (GS), must be leveraged against the non-reactive non-growth regions (NGS), laying the foundation of ASD. [6][7][8][9][10][11][12] If the deposition is done using ALD, this approach is referred to as AS-ALD. If the selectivity is lost following multiple cycles of processing, the technological utility of the method is diminished.…”

“…If the selectivity is lost following multiple cycles of processing, the technological utility of the method is diminished. Despite the fact that there are a number of successful attempts to alleviate this selectivity loss with small molecule inhibitors [7][8][9][10][11][12][13] (SMI) or incorporation of atomic layer etching (ALE) into ALD-ALE supercycles, [14][15][16][17] they all involve additional processing steps, and thus the nucleation remains at the focus of the need for fundamental understanding. The main problem in understanding the mechanistic origins of nucleation is that there is a variety of substrates used in deposition with various distributions of different surface reactive sites.…”