Synthesis and characterization of nitrogen-rich chemical vapor deposition precursors

Flores, Vincent Joseph

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https://hdl.handle.net/2142/130036 Copy

Description

Title

Synthesis and characterization of nitrogen-rich chemical vapor deposition precursors

Author(s)

Flores, Vincent Joseph

Issue Date

2025-07-15

Director of Research (if dissertation) or Advisor (if thesis)

Girolami, Gregory S

Doctoral Committee Chair(s)

Girolami, Gregory S

Committee Member(s)

• Abelson, John R
• Mirica, Liviu M
• Murphy, Catherine J

Department of Study

Chemistry

Discipline

Chemistry

Degree Granting Institution

University of Illinois Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Azides
• Triazenides
• Silatetrazolines
• Silicon-nitrides
• Transition metal-nitrides
• Chemical vapor deposition (CVD)

Abstract

The demand for conformal nitride films of transition metals (TMNx) and silicon (SiNx) grown at low temperatures for microelectronic devices has outpaced the development of suitably volatile, thermally balanced precursors. Existing precursor families: amidinate/guanidinate complexes for TMNx, and perhydrido- and halosilanes for SiNx, struggle to deposit impurity-free and conformal films at temperatures below 400 ℃. The work presented in this thesis pursues a ligand-centric solution, showing that nitrogen-rich azide-based ligands such as the 1,3-dialkyltriazenide and other azide-derived heterocycles provide a versatile synthetically accessible platform for volatile, thermally balanced vapor deposition precursors. Chapter 1 establishes the applicability of nitride films within modern microelectronics, optics, energy, and hard coating technologies. After outlining the key properties and device roles of SiNx and TMNx, a comparison between CVD, ALD, and PVD highlights how conformality, throughput, and thermal budget dictate technique choice. Particular emphasis is placed on single-source precursors for low-temperature CVD, with volatility, thermal stability, and clean deposition governing design constraints. The discussion culminates in the motivation for precursor design, detailing key principles and considerations used throughout this thesis. Chapter 2 describes the pursuit of a halide-free route to SiNx films with the synthesis of a single-source molecular silicon diazide compound. Thermogravimetric analysis shows single step volatilization with low residual mass, while prolonged heating of benzene-d6 solutions at 90 ℃ produces no detectable decomposition. Spectroscopy and XRD confirm the precursor to exclusively contain Si–N bonds at its center, minimizing the risk of carbon contamination from Si–C bonds. These data establish the compound as a promising single-source precursor for SiNx deserving further examination under CVD conditions. Chapter 3 builds upon key insights obtained from the investigations of Chapter 2. Three new nitrogen-rich silicon heterocycles, 1,4-dialkyl-5-silatetrazolines are synthesized and fully characterized. All sublime smoothly between 65 and 115 ℃ and exhibit single-step TGA mass losses with low residual mass, underscoring intact volatilization. The silatetrazoline motif provides a nitrogen-rich coordination environment offering a Si–N only route to SiNx, reducing possible carbon content and eliminating halide containing byproducts observed with amnio- and halosilanes. The chapter discusses correlations between structure and volatility, and positions these silatetrazolines as safe, higher nitrogen containing alternatives to conventional silane precursors. Chapter 4 marks a shift in focus to the 1,3-dialkyltriazenide ligand. After comparing their electronic features with isoelectronic amidinates and guanidinates, the volatility of known main group triazenide complexes are described along with the introduction of the first homoleptic, monomeric chromium(III) and iron(III) dialkyltriazenides. Both complexes were synthesized via a salt-metathesis reaction from Li(tBuN3tBu) and retain moderate volatility under sublimation conditions. The nearly parallel N-donor orbitals enhance chelation yet pose a risk of forming bridged species of lower volatility. The work presented in this chapter extends triazenide chemistry further into the transition metal series, potentially giving rise to volatile transition metal nitride precursors. Chapter 5 extended triazenide chemistry into lantern-type metal-metal complexes. The novel lithium 1-methyl-3-ethyltriazenide ligand was synthesized and used to prepare Co2(MeN3Et)4, the first binuclear lantern complex supported solely by asymmetric dialkyl triazenides. Single-crystal XRD reveals a 2.2563(3) Å Co–Co distance, among the shortest for a Co24+ core, and a 24° dihedral (N–Co–Co–N) twist from ideal D4h symmetry. Comparisons to reported DFT model systems as well as the only other known dicobalt triazenide lantern complex, suggests a singlet ground state with formal bond order ≈ 1, while magnetic and spectroscopic confirmation is underway.

Graduation Semester

2025-08

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/130036

Copyright and License Information

Copyright 2025 Vincent Flores

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