Graduate Thesis Or Dissertation
 

Nucleation Inhibiting Mechanisms in Atomic Layer Deposition of Nanolaminates

Public Deposited

Downloadable Content

Download PDF
https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/c821gs72p

Descriptions

Attribute NameValues
Creator
Abstract
  • Nucleation in atomic layer deposition (ALD) determines how many cycles are required to initiate growth and to form a continuous film. Nucleation has been exploited for the formation of nanoparticles, catalysts, and for area-selective ALD. Although sometimes overlooked or misrepresented in ALD reports, nucleation is also critical for multicomponent ALD and laminate ALD for ultra-thin metal/insulator/insulator/metal diodes. Here we demonstrate two types of nucleation behavior in ALD laminate films of Nb2O5 growth on ZnO, and Al2O3 growth on Nb2O5, and multiple methods of analysis for nucleation of nanolaminate films. ALD was performed in a Picosun SUNALE R-150B using alternating N2- purge-separated pulses of H2O as the first ALD precursor for each process and trimethylaluminum (TMA), diethylzinc (DEZ), and niobium ethoxide (NEO) as the second precursor for Al2O3, ZnO, and Nb2O5, respectively. Thickness of all films were measured using hi-res tunneling electron microscopy and variable-angle spectroscopic ellipsometry (VASE). On 4 nm and 25 nm of ZnO, nucleation delays were found to be ~10 and ~88 cycles, respectively. One likely explanation is the ZnO film morphology. For the 4 nm ZnO, crystal nuclei have not completely coalesced, forming a discontinuous arrangement of ZnO nano-islands, as is well-known for the diethyl-zinc (DEZ) and H2O process. For the 25 nm ZnO film, a more continuous ZnO surface results in increased Nb2O5 nucleation delay and reduced growth per cycle. The nucleation delay of Al2O3 on bare Si is ~0 cycles due to an abundance of surface hydroxyl groups with which the methyl groups readily undergo exchange reactions. Al2O3 nucleation delay is increased to ~10 cycles for a single cycle of underlying Nb2O5, decreasing to ~2 cycles for 20 or more cycles of Nb2O5. One possible explanation may be incomplete ligand dissociation of the niobium ethoxide (NEO) precursor. Increasing the number of underlying Nb2O5 cycles eventually forms a continuous surface by which Al2O3 nucleation delays decrease and eventually saturate. These examples of inhibited and enhanced nucleation emphasize the importance of understanding the early stages of ALD for laminate and multicomponent films.
Contributor
License
Resource Type
Date Issued
Degree Level
Degree Name
Degree Field
Degree Grantor
Commencement Year
Advisor
Committee Member
Academic Affiliation
Rights Statement
Publisher
Peer Reviewed
Language
Embargo reason
  • Intellectual Property (patent, etc.)
Embargo date range
  • 2021-12-18 to 2024-01-18

Relationships

Parents:

This work has no parents.

In Collection:

Items

Thumbnail Title Date Uploaded Visibility Actions
file details WitsellShaneMS2021.pdf 2021-12-17 Public Download