skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


  • NSF Public Access
  • Search Results
  • Selection Criteria for Small-Molecule Inhibitors in Area-Selective Atomic Layer Deposition: Fundamental Surface Chemistry Considerations
Title: Selection Criteria for Small-Molecule Inhibitors in Area-Selective Atomic Layer Deposition: Fundamental Surface Chemistry Considerations
Atomically precise and highly selective surface reactions are required for advancing microelectronics fabrication. Advanced atomic processing approaches make use of small molecule inhibitors (SMI) to enable selectivity between growth and nongrowth surfaces. The selectivity between growth and nongrowth substrates is eventually lost for any known combinations, because of defects, new defect formation, and simply because of a Boltzmann distribution of molecular reactivities on surfaces. The selectivity can then be restored by introducing etch-back correction steps. Most recent developments combine the design of highly selective combinations of growth and nongrowth substrates with atomically precise cycles of deposition and etching methods. At that point, a single additional step is often used to passivate the unwanted defects or selected surface chemical sites with SMI. This step is designed to chemically passivate the reactive groups and defects of the nongrowth substrates both before and/or during the deposition of material onto the growth substrate. This approach requires applications of the fundamental knowledge of surface chemistry and reactivity of small molecules to effectively block deposition on nongrowth substrates and to not substantially affect deposition on the growth surface. Thus, many of the concepts of classical surface chemistry that had been developed over several decades can be applied to design such small molecule inhibitors. This article will outline the approaches for such design. This is especially important now, since the ever-increasing number of applications of this concept still rely on trial-and-error approaches in selecting SMI. At the same time, there is a very substantial breadth of surface chemical reactivity analysis that can be put to use in this process that will relate the effectiveness of a potential SMI on any combination of surfaces with the following: selectivity; chemical stability of a molecule on a specific surface; volatility; steric hindrance, geometry, packing, and precursor of choice for material deposition; strength of adsorption as detailed by interdisplacement to determine the most stable SMI; fast attachment reaction kinetics; and minimal number of various binding modes. The down-selection of the SMI from the list of chemicals that satisfy the preliminary criteria will be decided based on optimal combinations of these requirements. Although the specifics of SMI selection are always affected by the complexity of the overall process and will depend drastically on the materials and devices that are or will be needed, this roadmap will assist in choosing the potential effective SMIs based on quite an exhaustive set of “SMI families” in connection with general types of target surfaces.  more » « less
Award ID(s):
2035154 2225900
PAR ID:
10491392
Author(s) / Creator(s):
;
Publisher / Repository:
ACS
Date Published:
Journal Name:
Accounts of Chemical Research
Volume:
56
Issue:
15
ISSN:
0001-4842
Page Range / eLocation ID:
2084 to 2095
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; (, Journal of Vacuum Science & Technology A)
    In area-selective processes, such as area-selective atomic layer deposition (AS-ALD), there is renewed interest in designing surface modification schemes allowing to tune the reactivity of the nongrowth (NG) substrates. Many efforts are directed toward small molecule inhibitors or atomic layers, which would modify selected surfaces to delay nucleation and provide NG properties in the target AS-ALD processes allowing for the manufacturing of smaller sized features than those produced with alternative approaches. Bromine termination of silicon surfaces, specifically Si(100) and Si(111), is evaluated as a potential pathway to design NG substrates for the deposition of metal oxides, and TiO2 (from cycles of sequential exposures of tetrakis-dimethylamido-titanium and water) is tested as a prototypical deposition material. Nucleation delays on the surfaces produced are comparable to those on H-terminated silicon that is commonly used as an NG substrate. However, the silicon surfaces produced by bromination are more stable, and even oxidation does not change their chemical reactivity substantially. Once the NG surface is eventually overgrown after a large number of ALD cycles, bromine remains at the interface between silicon and TiO2. The NG behavior of different crystal faces of silicon appears to be similar, albeit not identical, despite different arrangements and coverage of bromine atoms. 
    more » « less
  2. ; ; ; (, ChemPhysChem)
    Abstract As atomic layer deposition (ALD) emerges as a method to fabricate architectures with atomic precision, emphasis is placed on understanding surface reactions and nucleation mechanisms. ALD of titanium dioxide with TiCl4and water has been used to investigate deposition processes in general, but the effect of surface termination on the initial TiO2nucleation lacks needed mechanistic insights. This work examines the adsorption of TiCl4on Cl−, H−, and HO− terminated Si(100) and Si(111) surfaces to elucidate the general role of different surface structures and defect types in manipulating surface reactivity of growth and non‐growth substrates. The surface sites and their role in the initial stages of deposition are examined by X‐ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Density functional theory (DFT) computations of the local functionalized silicon surfaces suggest oxygen‐containing defects are primary drivers of selectivity loss on these surfaces. 
    more » « less
  3. (, University of Rochester)
    The fabrication of 2D devices with micro/nano-scale features often rely on assembly from a top-down perspective, where the design emphasis is on the removal of material to generate surface features. Common “top-down” approaches to fabrication often include “pattern and subtract” techniques which require energy-intensive processing and result in a high volume of material waste of substances such as photoresists, etchant, and developers. In addition to high energy and material dissipation, traditional “top-down” approaches have also struggled to adapt to the continuous downsizing of critical dimensions of 3D device components. Thus, instead of generating devices from a “top-down” perspective, there has been a push over the last two decades to instead leverage the intrinsic differences in chemical behavior between surface species, such that feature deposition selectively begins at the surface and grows vertically in an additive fashion via reaction from the “bottom-up”. Here, I will evaluate the ability of different small molecule and atomic layers to enable selective deposition on a silicon substrate. Specifically, I will be investigating a carbenylated organic molecule, a perfluorinated amine, and atomic halogen species on their ability to inhibit deposition atomic layer deposition (ALD) of a metal oxide. When paired with a hydrolyzed surface (which promotes metal oxide growth), these inhibiting species may be used to form complementary resist systems which can enable area-selective ALD (AS-ALD) on a surface. Another primary consideration in “bottom-up” approaches to feature fabrication is the ability to pattern these small molecule and atomic surface layers such that they form a template for selective growth. To this end, I will explore using ultrafast laser patterning and contact transfer printing to selectively deposit or alter these surface layers to generate complementary surface domains that can serve as a foundation for a AS-ALD platform. 
    more » « less
  4. ; ; (, Nanomaterials)
    Area-selective atomic layer deposition (AS-ALD) is a technique utilized for the fabrication of patterned thin films in the semiconductor industry due to its capability to produce uniform and conformal structures with control over thickness at the atomic scale level. In AS-ALD, surfaces are functionalized such that only specific locations exhibit ALD growth, thus leading to spatial selectivity. Self-assembled monolayers (SAMs) are commonly used as ALD inhibiting agents for AS-ALD. However, the choice of organic molecules as viable options for AS-ALD remains limited and the precise effects of ALD nucleation and exposure to ALD conditions on the structure of SAMs is yet to be fully understood. In this work, we investigate the potential of small molecule carboxylates as ALD inhibitors, namely benzoic acid and two of its derivatives, 4-trifluoromethyl benzoic acid (TBA), and 3,5-Bis (trifluoromethyl)benzoic acid (BTBA) and demonstrate that monolayers of all three molecules are viable options for applications in ALD blocking. We find that the fluorinated SAMs are better ALD inhibitors; however, this property arises not from the hydrophobicity but the coordination chemistry of the SAM. Using nanoscale infrared spectroscopy, we probe the buried monolayer interface to demonstrate that the distribution of carboxylate coordination states and their evolution is correlated with ALD growth, highlighting the importance of the interfacial chemistry in optimizing and assessing ALD inhibitors. 
    more » « less
  5. ; ; ; ; ; ; ; (, Materials Horizons)
    null (Ed.)
    The development of responsive soft materials with tailored functional properties based on the chemical reactivity of atomically precise inorganic interfaces has not been widely explored. In this communication, guided by first-principles calculations, we design bimetallic surfaces comprised of atomically thin Pd layers deposited onto Au that anchor nematic liquid crystalline phases of 4′- n -pentyl-4-biphenylcarbonitrile (5CB) and demonstrate that the chemical reactivity of these bimetallic surfaces towards Cl 2 gas can be tuned by specification of the composition of the surface alloy. Specifically, we use underpotential deposition to prepare submonolayer to multilayers of Pd on Au and employ X-ray photoelectron and infrared spectroscopy to validate computational predictions that binding of 5CB depends strongly on the Pd coverage, with ∼0.1 monolayer (ML) of Pd sufficient to cause the liquid crystal (LC) to adopt a perpendicular binding mode. Computed heats of dissociative adsorption of Cl 2 on PdAu alloy surfaces predict displacement of 5CB from these surfaces, a result that is also confirmed by experiments revealing that 1 ppm Cl 2 triggers orientational transitions of 5CB. By decreasing the coverage of Pd on Au from 1.8 ± 0.2 ML to 0.09 ± 0.02 ML, the dynamic response of 5CB to 1 ppm Cl 2 is accelerated 3X. Overall, these results demonstrate the promise of hybrid designs of responsive materials based on atomically precise interfaces formed between hard bimetallic surfaces and soft matter. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email