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Area‐selective atomic layer deposition (AS‐ALD) techniques are an emerging class of bottom‐up nanofabrication techniques that selectively deposit patterned ALD films without the need for conventional top‐down lithography. To achieve this patterning, most reported AS‐ALD techniques use a chemical inhibitor layer to proactively block ALD surface reactions in selected areas. Herein, an AS‐ALD process is demonstrated that uses a focused electron beam (e‐beam) to dissociate ambient water vapor and “write” highly resolved hydroxylated patterns on the surface of highly oriented pyrolytic graphite (HOPG). The patterned hydroxylated regions then support subsequent ALD deposition. The e‐beam functionalization technique facilitates precise pattern placement through control of beam position, dwell time, and current. Spatial resolution of the technique exceeded 42 nm, with a surface selectivity of between 69.9% and 99.7%, depending on selection of background nucleation regions. This work provides a fabrication route for AS‐ALD on graphitic substrates suitable for fabrication of graphene‐based nanoelectronics.
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Application and patterning of atomic and small-molecule resists for area-selective deposition on silicon
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.
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- Award ID(s):
- 2225896
- PAR ID:
- 10584894
- Publisher / Repository:
- University of Rochester
- Date Published:
- Format(s):
- Medium: X
- Institution:
- University of Rochester
- Sponsoring Org:
- National Science Foundation
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For continual scaling in microelectronics, new processes for precise high volume fabrication are required. Area-selective atomic layer deposition (ASALD) can provide an avenue for self-aligned material patterning and offers an approach to correct edge placement errors commonly found in top-down patterning processes. Two-dimensional transition metal dichalcogenides also offer great potential in scaled microelectronic devices due to their high mobilities and few-atom thickness. In this work, we report ASALD of MoS2 thin films by deposition with MoF6 and H2S precursor reactants. The inherent selectivity of the MoS2 atomic layer deposition (ALD) process is demonstrated by growth on common dielectric materials in contrast to thermal oxide/ nitride substrates. The selective deposition produced few layer MoS2 films on patterned growth regions as measured by Raman spectroscopy and time-of-flight secondary ion mass spectrometry. We additionally demonstrate that the selectivity can be enhanced by implementing atomic layer etching (ALE) steps at regular intervals during MoS2 growth. This area-selective ALD process provides an approach for integrating 2D films into next-generation devices by leveraging the inherent differences in surface chemistries and providing insight into the effectiveness of a supercycle ALD and ALE process.more » « less
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Accepted Manuscript1.0
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