Area-selective Deposition Research Articles

Modeling of Masked Droplet Deposition for Site-Controlled Ga Droplets.

Site-controlled Ga droplets on AlGaAs substrates are fabricated using area-selective deposition of Ga through apertures in a mask during molecular beam epitaxy (MBE). The Ga droplets can be crystallized into GaAs quantum dots using a crystallization step under As flux. In order to model the complex process, including the masked deposition of the droplets and a reduction of their number during a thermal annealing step, a multiscale kinetic Monte Carlo (mkMC) simulation of self-assembled Ga droplet formation on AlGaAs is expanded for area-selective deposition. The simulation has only two free model parameters: the activation energy for surface diffusion and the activation energy for thermal escape of adatoms from a droplet. Simulated droplet numbers within the opening of the aperture agree quantitatively with the experimental results down to the perfect site-control, with one droplet per aperture. However, the model parameters are different compared to those of the self-assembled droplet growth. We attribute this to the presence of the mask in close proximity to the surface, which modifies the local process temperature and the As background. This approach also explains the dependence of the model parameters on the size of the aperture.

Area-Selective Deposition of AlOx and Al-Silicate for Fully Self-Aligned Via Integration

The rush for better-performing electronics, and manufacturing processes that heavily rely on "top-down" patterning techniques, is making the integration of "self-aligned" fabrication methods, such as area-selective deposition (ASD), a critical objective for continued device scaling. The fully self-aligned via (FSAV) scheme is broadly proposed as a "killer application" to determine whether ASD can shift from an R&D process to high-volume manufacturing. Nevertheless, the lack of a suitable low-κ deposition process has prevented the realization of FSAV by dielectric-on-dielectric ASD. This is primarily due to the high temperature and/or strong oxidizers employed during low-κ dielectric deposition and their unsuitability in the presence of organic masks, such as self-assembled monolayers (SAMs), used to prevent material nucleation during ASD. In this work, AlOx and Al-silicate atomic layer deposition (ALD) processes are studied to provide suitable materials for ASD-enabled FSAV. Dimethylaluminum isopropoxide and H2O are utilized to deposit the metal oxide, whereas Al-silicate is grown by adding 2,2-dimethoxy-1,6-diaza-2-silacyclooctane (DMDAcO) pulses to the AlOx ALD cycle. The selectivity of such processes is demonstrated on 50 nm Cu/SiO2 structures, using octadecanethiol-derived SAMs to inhibit material nucleation on the metal lines. Scanning and transmission electron microscopies are employed to assess the quality of the ASD processes and investigate the mechanisms behind defect generation on a nongrowth surface. X-ray photoelectron spectroscopy measurements show the high purity of the AlOx film, whereas DMDAcO-ligand incorporation into the Al-silicate matrix is observed. Planar capacitor structures are used to assess the electrical properties of both ASD films, revealing that the silicate film exhibits a relatively low κ-value (5.3 ± 0.2), with a high acceleration field factor (32.4 ± 1.4) and a dielectric breakdown voltage of 6.0 ± 0.3 V at 100 °C.

Gradient area-selective deposition for seamless gap-filling in 3D nanostructures through surface chemical reactivity control

The integration of bottom-up fabrication techniques and top-down methods can overcome current limits in nanofabrication. For such integration, we propose a gradient area-selective deposition using atomic layer deposition to overcome the inherent limitation of 3D nanofabrication and demonstrate the applicability of the proposed method toward large-scale production of materials. Cp(CH3)5Ti(OMe)3 is used as a molecular surface inhibitor to prevent the growth of TiO2 film in the next atomic layer deposition process. Cp(CH3)5Ti(OMe)3 adsorption was controlled gradually in a 3D nanoscale hole to achieve gradient TiO2 growth. This resulted in the formation of perfectly seamless TiO2 films with a high-aspect-ratio hole structure. The experimental results were consistent with theoretical calculations based on density functional theory, Monte Carlo simulation, and the Johnson-Mehl-Avrami-Kolmogorov model. Since the gradient area-selective deposition TiO2 film formation is based on the fundamentals of molecular chemical and physical behaviours, this approach can be applied to other material systems in atomic layer deposition.

Area-selective atomic layer deposition of high-quality Ru thin films by chemo-selective adsorption of short alkylating agents

We report the effects of surface modification by vapor dosing of (N,N-diethylamino)trimethylsilane (DEATMS) molecules as short alkylating agents on technologically important substrates of Si, SiO2, TiN, and W. In this study, tricarbonyl(trimethylenemethane) ruthenium [Ru(TMM)(CO)3] was employed as a metal–organic precursor for atomic layer deposition (ALD) of Ru, which produced high-quality Ru films with significantly low resistivity and high growth-per-cycle. Through surface modification of vapor-dosed DEATMS molecules, significant growth retardation against the ALD Ru process was selectively found on SiO2 and TiN in contrast to Si(-H) and W substrates. With applying chemo-selectively inhibitory characteristics, we successfully demonstrate area selective deposition of ALD Ru films on a patterned TiN/Si substrate.

Area selective deposition of ruthenium on 3D structures

Trends in device miniaturization have driven the adoption of new materials that, in turn, have enabled significant advancements in the field of process engineering and integration for semiconductor technology. Continued progress for device scaling is necessary and can be enabled by advances in lithographic techniques and deposition schemes. Thin-film deposition for spacers and etch stop layers has become a mainstay to enable and extend traditional 2D scaling into the 3D realm for fabricating advanced semiconductor devices. For processing 3D structures, controlled film deposition with subnanometer resolution in high aspect ratio features is desired. Area selective deposition (ASD) can be a powerful response to such a challenge. ASD is a type of thin-film deposition technique scheme that can be used to eliminate the need for several expensive and time-consuming lithography steps with fewer performance penalties. In this work, we show ASD of ruthenium (Ru) on 3D molybdenum (Mo)–silicon oxide (SiO2) stacks by utilizing the inherent substrate preference of the Ru precursor to a H-terminated surface. In the best selectivity condition, our results show growth of ∼5 nm Ru on Mo, with no film growth on SiO2. Changes in Ru growth kinetics were observed after dilute hydrofluoric acid (DHF) treatment for both surfaces. Post-DHF treatment, the Ru growth rate on Mo was reduced by 5%. However, on SiO2 (after incubation delay), the growth rate was reduced by 94% compared to untreated surfaces. This translates to a very high difference in the growth rate of Ru on Mo vs SiO2, even after considering the incubation delay. Finally, by using 3D topologies with high aspect ratio holes, we have highlighted that it is important to deconvolute the effects of precursor depletion and selectivity. To the best of our knowledge, this is the first demonstration of ASD of Ru on 3D structures without the use of any blocking layers. Therefore, these results demonstrate a new paradigm for ASD in 3D features.

Packing of inhibitor molecules during area-selective atomic layer deposition studied using random sequential adsorption simulations

Area-selective atomic layer deposition (ALD) is of interest for applications in self-aligned processing of nanoelectronics. Selective deposition is generally enabled by functionalization of the area where no growth is desired with inhibitor molecules. The packing of these inhibitor molecules, in terms of molecule arrangement and surface density, plays a vital role in deactivating the surface by blocking the precursor adsorption. In this work, we performed random sequential adsorption (RSA) simulations to investigate the packing of small molecule inhibitors (SMIs) on a surface in order to predict how effective the SMI blocks precursor adsorption. These simulations provide insight into how the packing of inhibitor molecules depends on the molecule size, molecule shape, and their ability to diffuse over the surface. Based on the RSA simulations, a statistical method was developed for analyzing the sizes of the gaps in between the adsorbed inhibitor molecules, serving as a quantitative parameter on the effectiveness of precursor blocking. This method was validated by experimental studies using several alcohol molecules as SMIs in an area-selective deposition process for SiO2. It is demonstrated that RSA simulations provide an insightful and straightforward method for screening SMIs in terms of their potential for area-selective ALD.

Quartz crystal microbalance gravimetry measurements of the sorption of trimethylaluminum into polystyrene and poly(methyl methacrylate)

The sorption behavior of metalorganic species into polymers is important in various gas-phase processes including vapor phase infiltration (VPI) which is used to transform organic polymers into organic-inorganic hybrid materials and area-selective deposition where various organic layers are used to prevent vapor deposition. In this work, we use in situ quartz crystal microbalance (QCM) gravimetry to measure the long-term mass uptake of TMA into polystyrene (PS) and compare it with that of poly (methyl methacrylate) [PMMA]. While TMA infiltration into PMMA, PS, and PMMA-PS copolymers is widely studied, a direct investigation of TMA's long term sorption behavior into pure PS has not previously been reported. During a 17.5 h TMA exposure step, PMMA is found to sorb 0.67–0.83 ng of TMA per nanogram of polymer while PS is found to sorb only 0.02 ng per nanogram polymer. These results clarify that the mechanism for low TMA infiltration into PS is a lack of sorption rather than rapid out-diffusion of the precursor. This result has implications ranging from designing impermeable layers for selective area deposition to predicting mass transport during vapor infiltration into ordered block copolymers. Here, the poor sorption of TMA into PS is utilized in a demonstration to pattern inorganic infiltration into PET films.

Compatibility between polymethacrylate-based extreme ultraviolet resists and TiO2 area-selective deposition

BackgroundExtreme ultraviolet (EUV) lithography is crucial to achieving smaller device sizes for next-generation technology, although organic resists face substantial challenges, such as low etch resistance, which limit the resolution of smaller features.AimEvaluate the potential for area-selective deposition (ASD) to improve EUV pattern resolution (e.g., by increasing etch resistance).ApproachWe evaluate thermal compatibility, atomic layer deposition growth rate, and selectivity for TiO2 ASD on various organic EUV resist materials using water contact angle, Rutherford backscattering spectrometry, and X-ray photoelectron spectroscopy. The effects of photo-acid generator (PAG) and EUV exposure on polymer properties and selectivity are considered.ResultsThe organic resist materials studied demonstrate thermal compatibility with TiO2 ALD (125°C for 60 min). The TiO2 ALD process from TiCl4 and H2O proceeds readily on poly(tert-butyl methacrylate), poly(p-hydroxystyrene), and poly(p-hydroxystyrene-random-methacrylic acid) polymers, with and without PAG incorporation, in either the as-formed or EUV exposed state. However, TiO2 is inhibited on poly(cyclohexyl methacrylate).ConclusionsWe demonstrate that as-formed EUV resists can serve as either the growth or nongrowth surface during TiO2 ASD, thereby enabling resist hardening and tone inversion applications, respectively. These results serve as a basis for further ASD studies on EUV resist materials to improve pattern resolution in next-generation devices.

Quantification of area-selective deposition on nanometer-scale patterns using Rutherford backscattering spectrometry

We present a site-specific elemental analysis of nano-scale patterns whereby the data acquisition is based on Rutherford backscattering spectrometry (RBS). The analysis builds on probing a large ensemble of identical nanostructures. This ensures that a very good limit of detection can be achieved. In addition, the analysis exploits the energy loss effects of the backscattered ions within the nanostructures to distinguish signals coming from different locations of the nanostructures. The spectrum deconvolution is based on ion-trajectory calculations. With this approach, we analyse the Ru area-selective deposition on SiO2-TiN line-space patterns with a linewidth of 35 nm and a pitch of 90 nm. We quantify the selectivity and the Ru local areal density on the top versus on the sidewall of the SiO2 lines. The sensitivity to probe ruthenium deposited on the various surfaces is as low as 1013 atoms/cm2. The analysis is quantitative, traceable, and highly accurate thanks to the intrinsic capabilities of RBS.

Low temperature, area-selective atomic layer deposition of NiO and Ni

Nickel and nickel oxide are utilized within various device heterostructures for chemical sensing, solar cells, batteries, etc. Recently, the rising interest in realizing low-cost, flexible electronics to enable ubiquitous sensors and solar panels, next-generation displays, and improved human-machine interfaces has driven interest in the development of low-temperature fabrication processes for the integration of inorganic devices with polymeric substrates. Here, we report the low-temperature area-selective atomic layer deposition of Ni by reduction of preformed NiO. Area-selective deposition of NiO is performed at 100 °C using bis(N,N'-di-tert-butylacetamidinato) nickel(II) and water on SiO2 and polystyrene. NiO grows two-dimensionally and without nucleation delay on oxide substrates but not on SiNx or polystyrene, which require surface treatments to promote NiO nucleation. Additionally, prepatterned sp2 carbon-rich resists inhibit the nucleation of NiO, and in this way, carbon-free NiO may be patterned. Subsequent thermal reduction of NiO to Ni was investigated using H2 (50–80 m Torr) and thermally generated H-atoms (3 × 10−5 Torr chamber pressure). Due to the relatively high free surface energy of Ni metal, Ni films undergo dewetting at elevated temperatures when solid-state transport is enabled. Reduction of NiO to Ni is demonstrated at 100 °C and below using atomic hydrogen. In situ x-ray photoelectron spectroscopy is used to determine oxidation state and ex situ x-ray reflectivity and atomic force microscopy are used to probe the film thickness and surface morphology, respectively.

(Invited) Introduction and Overview of Area-Selective Thin Film Deposition

Low temperature Area-Selective Deposition (ASD) is becoming an important need in semiconductor manufacturing to augment photolithography for improved resolution and alignment of printed features. Area-selective deposition is used routinely at temperature in excess of 800°C to form epitaxial transistor contacts, but for back-end applications, new ASD processes are needed that work at <400°C. This tutorial will introduce the challenges of low temperature ASD, and summarize recent advances in this field, including ASD via Atomic Layer Deposition (ALD) and Chemical Vapor Deposition (CVD), and understanding of feature size dependence and lateral “mushroom” growth. We will review approaches using surface passivation, including self-assembled monolayers and small molecule inhibitors, as well as approaches based on inherent differences in nucleation on different clean surfaces. Further, we will present emerging approaches that achieve patterning by taking advantage of native selectivity in nucleation and etching reactions, for example, where ALD and Atomic Layer Etching (ALE) can be combined, either in sequence or in parallel, to achieve desired outcomes. We will also review current modeling efforts, including methods to quantitatively analyze ASD and compare results for different materials and different processes, highlighting the challenges of understanding reactions for initial nucleation and nucleus removal.

(Invited) Nm-Scale Patterns and Selectivity: A Blessing or a Curse

Area-selective deposition (ASD) is a promising technique for semiconductor device manufacturing. The replication of nanoscale patterns by ASD can simplify device fabrication process flows by reducing the number of lithography, etch and chemical-mechanical polishing steps. In addition, ASD could eliminate pattern overlay errors. ASD is of special interest as device dimensions scale and has recently been shown as viable approach for the fully self-aligned via, to enable interconnect scaling beyond the 3 nm node [1]. However, the dependence of the selectivity of ALD and CVD processes on the patterning process and pattern dimensions is poorly documented. This aspect will be investigated in the current presentation. We will discuss the fundamental mechanisms of ALD growth mechanisms and how they influence selectivity. Next, we will discuss an example of Ru ASD with defect mitigation in nm-scale patterns on full 300-mm wafers [2].[1] Chen et al., IEDM21, 486-489.[2] Clerix et al., Adv. Mater. Interfaces 2021, 2100846.

Growth behavior and substrate selective deposition of polypyrrole, polythiophene, and polyaniline by oxidative chemical vapor deposition and molecular layer deposition

Bottom-up self-aligned area-selective deposition (ASD) plays an important role in patterning of advanced electronic devices. Specifically, ASD of organic materials can be utilized for nucleation inhibitors, sacrificial layers, and air-gap materials for next-generation nanoscale processing. This work introduces fundamental growth behavior of various conjugated polymers including polypyrrole, polythiophene, and polyaniline via oxidative molecular layer deposition and chemical vapor deposition. Effects of process parameters on film properties are described, and ASD behavior of different polymers are quantitatively characterized. These findings expand fundamental understanding of conjugated polymer deposition and provide new perspectives for ASD of organic thin films.

Growth chemistry and electrical performance of ultrathin alumina formed by area selective vapor phase infiltration

Abstract 1 1 Commercial equipment is identified in this report in order to specify the experimental procedure adequately and does not imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the equipment identified is necessarily the best available for the purpose. The growth chemistry and electrical performance of 5 nm alumina films, fabricated via the area-selective vapor phase infiltration (VPI) of trimethylaluminum into poly(2-vinylpyridine), are compared to a conventional plasma enhanced atomic layer deposition (PEALD) process. The chemical properties are assessed via energy dispersive X-ray spectroscopy and hard X-ray photoelectron spectroscopy measurements, while current – voltage dielectric breakdown and capacitance – voltage analysis is undertaken to provide electrical information of these films for the first time. The success and challenges in dielectric formation via polymer VPI, the compatibility of pyridine in such a role, and the ability of the unique and rapid grafting-to polymer brush method in forming coherent metal oxides is evaluated. It was found that VPI made alumina fabricated at temperatures between 200 and 250 °C had a consistent breakdown electrical field, with the best performing devices possessing a к value of 5.9. The results indicate that the VPI approach allows for the creation of alumina films that display dielectric properties of a comparable quality to conventional PEALD grown films. • Dielectrics grown by VPI of poly(2-vinylpyridine) electrically characterised for the first time. • Best performing VPI-made Al 2 O 3 competes in performance to conventional ALD. • IV breakdown reveals a high consistency in electrical properties is possible. • Process is low temperature and compatible in area selective deposition. • CV and HAXPES analysis reveal the next challenges for industry integration.

Thermally Annealed Molecular Layer‐Deposited Indicone: Structural Analysis and Area Selective Deposition Application

AbstractSemiconductor devices have become smaller, more complicated, and structuralized in three dimensions. Area selective deposition is one of the promising bottom‐up process techniques for self‐alignment or improved overlay to achieve errorless alignment. The surface chemistry is crucial to adjust precursor adsorption. In this research, graphitic carbon fabricated by molecular layer deposition is utilized for inhibiting precursor adsorption. An indicone film, which has an indium‐based metalcone structure, is fabricated using bis(trimethysily)‐amidodiethylindium and hydroquinone. The structure of the indicone film is reconstructed to graphitic carbon with a small oxygen content on the surface by a thermal annealing process. The atomic structures of as‐dep and thermally‐annealed indicone films are analyzed. The organic structure is transformed to graphitic carbon above an annealing temperature of 450 °C, where indium is completely removed with annealing temperatures above 600 °C. The thermally‐annealed indicone is used for deactivating film growth, which can delay 60 cycles of ZnO growth (equivalent to a thickness of ≈11 nm). In addition, to energetically demonstrate precursor adsorption on graphitic carbon, the density functional theory is utilized. Finally, ZnO as a blocking layer is selectively deposited on a grated line pattern to interconnect the SiO2 line pattern by transferring a hard mask.

Temporal and spatial atomic layer deposition of Al-doped zinc oxide as a passivating conductive contact for silicon solar cells

Recently, stacks consisting of an ultrathin SiO2 coated with atomic-layer-deposited (ALD) Al-doped zinc oxide (ZnO:Al) have been shown to yield state-of-the-art passivation of n-type crystalline silicon surfaces and provide low contact resistivities to n+-doped Si and poly-Si surfaces. Key for achieving good surface passivation are an intentionally-grown SiO2 interlayer, an aluminum oxide (Al2O3) capping layer and a post-deposition anneal, whereas n-type doping of the ZnO is required to achieve a low contact resistivity. In this work, we present the latest results and insights obtained for this contact stack. This includes a study of the minimum required thicknesses of both the ZnO and the Al2O3 capping layer to achieve a high passivation level after post-deposition anneal. Also, we provide details on how to remove the Al2O3 capping layer selectively from the ZnO:Al after the post-deposition anneal using a pH-controlled wet-etch, such that the ZnO:Al can be contacted by a metal. Whereas previous work was based on lab-scale temporal ALD, in this work we highlight the industrialization potential by demonstrating that these layers can be prepared by spatial ALD, yielding good passivation levels on both undiffused n-type and n+-diffused c-Si surfaces. Finally, we demonstrate the capability of ALD to deposit ZnO:Al layers selectively on oxidized regions of an otherwise HF-last treated c-Si surface. Such area-selective deposition opens up potential pathways for local, self-aligned contact formation. Altogether, this work provides valuable insights into the working mechanism and practical aspects of ZnO:Al-based passivating contacts.

Self-assembled monolayers as inhibitors for area-selective deposition: A novel approach towards resist-less EUV lithography

Patterning below 10 nm with conventional techniques such as Litho-etch (LE*), a subtractive self-aligned multiple patterning process, suffers from limitations due to edge placement errors, decreasing throughput, complexity, pattern collapse, photoresist non-uniformity. Bottom-up processes for fabrication of nano devices by means of Area selective deposition (ASD) are peaking up over top-down approaches to mitigate most of the above-mentioned problems. One of the ways to achieve ASD of an hardmask is by using extreme ultra-violet (EUV, λ-13.5 nm) lithography to single-step pattern self-assembled monolayers (SAM) on a photosensitive substrate (or layer) followed by atomic layer deposition (ALD). In this work, photo-catalytically active titanium oxide is considered as substrate for the deposition of organosilane SAMs of different chain length. Upon exposure to EUV, fragmentation of SAM’s molecules is observed though a mechanism involving electron/hole pair exchange from TiO2. This induces changes in the chemistry of the exposed area, allowing an ALD deposition in the SAM-cleared areas.

Mechanisms for undesired nucleation on H-terminated Si and dimethylamino-trimethylsilane passivated SiO2 during TiO2 area-selective atomic layer deposition

During TiO2 atomic layer deposition (ALD) using TiCl4 and H2O at ∼150 °C, nucleation proceeds rapidly on hydroxylated SiO2 but is inherently delayed on passivated surfaces such as H-terminated silicon (Si-H) and trimethylsilyl-passivated SiO2 (SiO2-TMS) formed using dimethylamino-trimethylsilane (DMA-TMS) as a small molecule inhibitor. In this work, we explore details of TiO2 nucleation on both Si-H and SiO2-TMS and show that the mechanisms leading to unwanted nuclei depend strongly on the passivation mechanism. Initial growth is observed as a function of ALD cycles using scanning electron microscopy to obtain average particle size, density, and overall surface coverage fraction. Also, average film thickness vs cycle is estimated using ellipsometry or Rutherford backscattering spectrometry. Data are compared to an analytical model that considers that either nucleation sites are present on the starting non-growth surface or sites are generated during the ALD process. On the Si-H surface, data and modeling indicate that nucleation occurs predominantly from a fixed number of nucleation sites present on the starting growth surface that start to immediately grow. However, on TMS-passivated SiO2, nucleation sites are predominantly generated during the growth process so that the density of nucleation sites increases as growth proceeds. Results indicate that nucleation sites are created when adsorbed ALD reactants become kinetically trapped on the SiO2-TMS surface. This demonstrates that mechanisms associated with unwanted nucleation during area-selective deposition (ASD) can depend on details of the surface passivation scheme, thereby providing insight to help to improve ASD strategies for advanced applications.

(Dielectric Science & Technology Thomas Callinan Award) Materials and Processes As Enablers for Moore Moore and Beyond Moore Technologies

In this presentation, an overview will be presented of historic and recent developments achieved w.r.t. materials and processes that enabled continued performance scaling of CMOS and beyond CMOS applications. Starting from early high-k work. For decades, thermal oxidation of crystalline Silicon into SiO2 has been the gate oxide material in CMOS technology. Miniaturization for performance improvement, required the gate dielectric to decrease in thickness to support the required increase in capacitance (per unit area) and drive current (per device width). Early 2000, the thickness scaled below 1.5 nm, causing drastically increased leakage currents, high power consumption and reduced device reliability. Replacing the SiO2 gate dielectric with a high-κ (dielectric constant) material allows increased gate capacitance without the associated leakage effects. Activities involved the unit process step development of dielectric and metal deposition processes, advanced interface preparation, electrical and physical characterization and wet and dry etch process development. In a second section, emphasis will be on emerging nanomaterials. Nanotechnology is defined as the manipulation of matter with at least one dimension sized from below 100nm, thus all CMOS activities are functional nanotechnology. The latter concentrated initially on Graphene, but extended further towards Transition Metal Dicalchogenide Materials. Emphasis of the work will be on growth, functionalization, dielectric passivation and doping of these materials. Lastly, expanding on the nanomaterial know-how also progress with regard to low-k dielectrics, area selective deposition processes (for bottom-up lithography) and application of nanochemistry research for photoresist material screening, where chemical interactions at the nanoscale, related to the EUV lithography (radiation chemistry) are hampering the pattern scaling.Throughout the presentation, recognition will be given to people (PhD students) that contributed to this work and the presentation is also in honor of Prof Dolf Landheer and Professor Samares Kar with whom I organized my first ECS symposium.

(Invited) Coordination Controlled Electrodeposition of Metal Nanostructures

It is the combination of features related to surface chemistry, charge transfer, and interfacial energies which makes self-assembled monolayers (SAMs) attractive templates for electrodeposition. However, as in other additive processes such as atomic layer or electroless deposition where SAMs are harnessed for area selective deposition, one is faced with substantial challenges when advancing to the ultrasmall scale. Based on defects in a chemically inert SAM, the established scheme of SAM controlled electrodeposition offers a very convenient way to generate patterns but is only applicable down to the length scale of a few tens of nanometers. The statistical nature of defects does not provide the level of control over the deposition process required to move further towards the bottom range of the nanoscale.For this reason we have been exploring a deposition scheme which builts on features intrinsic to the SAM molecules and, therefore, promises a more precise control over decisive steps in the deposition process.1 The essential point is the paradigm shift from a mushroom like deposition at defects to a deposition via coordinated metal ions using a suitably functionalized SAM. As illustrated in the cartoon, nuclei generated by discharging a two-dimensional layer of ions act as seeds for the deposition from the bulk electrolyte. Yielding layers on top of the SAM, this coordination controlled deposition not only enables a further reduction in lateral dimensions of patterns to below 20 nm but also shifts the percolation threshold, yielding continuous layers at a thickness of about 2 nm. In relation to this the average roughness of below 0.4 nm is substantial and further improvement is needed. Key to this and a further reduction in dimensions is the understanding of the processes determining the seed formation and how these can be controlled by the design of the SAM. Informed by calculations which show a strong interaction between metal atoms and the terminating aromatic unit of the SAM,2 studies of binary layers consisting of coordinating and non-coordinating molecules have been performed. The average size and size distribution of the particles depend on the composition and mixing ratio, and a significant reduction in size to about 2 nm can be achieved, suggested that the diffusion length is reduced and nucleation is promoted in mixed SAMs. The results show that SAMs provide a range of design opportunities through which coordination controlled electrodeposition can be further developed towards ultrasmall structures.1. Z. She, Z. Yao, H. Ménard, S. Tobish, D. Lahaye, N. R. Champness, M. Buck, Coordination controlled electrodeposition and patterning of layers of palladium/copper nanoparticles on top of a self-assembled monolayer, Nanoscale 11, 13773-13782 (2019).2. Z. Yao, M. Buck, M. Bühl, A Density Functional Theory Study of Pd Aggregation on a Pyridine-Terminated Self-Assembled Monolayer, Chem. Eur. J. 26, 10555-10563 (2020). Figure 1