Multilayer model for determining the thickness and refractive index of sol–gel coatings via laser ellipsometry

Loke, Vincent L. Y.; Riefler, Norbert; Mehner, A.; Prenzel, Torsten; Hoja, Timo; Wriedt, Thomas; Mädler, Lutz

doi:10.1016/j.tsf.2012.12.038

Cited by 4 publications

(5 citation statements)

References 20 publications

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“…24 However, there are a few previous studies that show inhomogeneities in sol−gel-derived multilayer films observable by TEM 25 or X-ray reflectivity (XRR). 26,27 Denser surface "crusts" in single-layer films have also been observed via ellipsometry in sol−gel silica coatings 28 and by XRR in PIC aluminum oxide phosphate films. 29 The nature of these inhomogeneities, whether due to density variations or compositional inhomogeneity, has not been determined.…”

Section: ■ Introductionmentioning

confidence: 93%

“…Although fundamentally different chemistries occur in the various methods used to prepare inorganic films, drying and densification models generally assume the resulting films are homogeneous . However, there are a few previous studies that show inhomogeneities in sol–gel-derived multilayer films observable by TEM or X-ray reflectivity (XRR). , Denser surface “crusts” in single-layer films have also been observed via ellipsometry in sol–gel silica coatings and by XRR in PIC aluminum oxide phosphate films . The nature of these inhomogeneities, whether due to density variations or compositional inhomogeneity, has not been determined.…”

Section: Introductionmentioning

confidence: 99%

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Non-uniform Composition Profiles in Inorganic Thin Films from Aqueous Solutions

Fairley

Merrill

Woods

et al. 2015

ACS Appl. Mater. Interfaces

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A variety of metal oxide films (InGaOx, AlOx, "HafSOx") prepared from aqueous solutions were found to have non-uniform electron density profiles using X-ray reflectivity. The inhomogeneity in HafSOx films (Hf(OH)4-2x-2y(O2)x(SO4)y·zH2O), which are currently under investigation as inorganic resists, were studied in more detail by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and medium-energy ion scattering (MEIS). The HAADF-STEM images show a greater concentration of heavy atoms near the surface of a single-layer film. MEIS data confirm the aggregation of Hf at the film surface. The denser "crust" layer in HafSOx films may directly impact patterning resolution. More generally, the phenomenon of surface-layer inhomogeneity in solution-deposited films likely influences film properties and may have consequences in other thin-film systems under investigation as resists, dielectrics, and thin-film transistor components.

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Section: ■ Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Non-uniform Composition Profiles in Inorganic Thin Films from Aqueous Solutions

Fairley

Merrill

Woods

et al. 2015

ACS Appl. Mater. Interfaces

View full text Add to dashboard Cite

show abstract

“…A variety of approaches have been used to gain insight into the structure of amorphous films, including X-ray reflectivity (XRR), − ellipsometry, grazing incidence X-ray diffraction (GIXRD), transmission electron microscopy (TEM), electron diffraction, high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), , extended X-ray absorption fine structure spectroscopy (EXAFs), , and solid-state nuclear magnetic resonance (ss-NMR). , Although these traditional techniques provide a variety of structural details, there remains a distinct deficiency in accurately determining the local and mid-range atomic structure of nanostructured materials. X-ray total scattering measurements and pair distribution function (PDF) analysis have yielded significant structural information about bulk amorphous and nanostructured materials, specifically in determining local to long-range order. − However, there has been much less reported use of PDF analysis to examine thin films on a substrate, due to complicated data analysis procedures and assumptions required about the sample volume and geometry. , Additionally, in the case of amorphous metal oxides, the low scattering power of O further complicates X-ray structural studies.…”

Section: Introductionmentioning

confidence: 99%

“…A variety of approaches have been used to gain insight into the structure of amorphous films, including X-ray reflectivity (XRR), 17−19 ellipsometry, 20 grazing incidence X-ray diffraction (GIXRD), 21 transmission electron microscopy (TEM), 22 electron diffraction, 23 high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), 24,25 extended X-ray absorption fine structure spectroscopy (EXAFs), 26,27 and solid-state nuclear magnetic resonance (ss-NMR). 28,29 Although these traditional techniques provide a variety of structural details, there remains a distinct deficiency in accurately determining the local and mid-range atomic structure of nanostructured materials.…”

Section: ■ Introductionmentioning

confidence: 99%

Same Precursor, Two Different Products: Comparing the Structural Evolution of In–Ga–O “Gel-Derived” Powders and Solution-Cast Films Using Pair Distribution Function Analysis

et al. 2017

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Amorphous metal oxides are central to a variety of technological applications. In particular, indium gallium oxide has garnered attention as a thin-film transistor channel layer material. In this work we examine the structural evolution of indium gallium oxide gel-derived powders and thin films using infrared vibrational spectroscopy, X-ray diffraction, and pair distribution function (PDF) analysis of X-ray total scattering from standard and normal incidence thin-film geometries (tfPDF). We find that the gel-derived powders and films from the same aqueous precursor evolve differently with temperature, forming mixtures of Ga-substituted InO and In-substituted β-GaO with different degrees of substitution. X-ray total scattering and PDF analysis indicate that the majority phase for both the powders and films is an amorphous/nanocrystalline β-GaO phase, with a minor constituent of InO with significantly larger coherence lengths. This amorphous β-GaO phase could not be identified using the conventional Bragg diffraction techniques traditionally used to study crystalline metal oxide thin films. The combination of Bragg diffraction and tfPDF provides a much more complete description of film composition and structure, which can be used to detail the effect of processing conditions and structure-property relationships. This study also demonstrates how structural features of amorphous materials, traditionally difficult to characterize by standard diffraction, can be elucidated using tfPDF.

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“…Despite the inherent differences between organic sol–gel and aqueous deposition routes, density inhomogeneities have been observed in films derived from both solution deposition methods. − Recently, we reported the first in-depth chemical analysis of nonuniform density profiles in aqueous-derived thin films . Specifically, Hf enrichment at the surface of hafnium sulfate oxide (HafSOx) films was observed, and the denser, more condensed surface layer was attributed to enhanced evaporation at the film surface.…”

Section: Introductionmentioning

confidence: 99%

Nonuniform Composition Profiles in Amorphous Multimetal Oxide Thin Films Deposited from Aqueous Solution

Woods

Thomas

Mitchson

et al. 2017

ACS Appl. Mater. Interfaces

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Metal oxide thin films are ubiquitous in technological applications. Often, multiple metal components are used to achieve desired film properties for specific functions. Solution deposition offers an attractive route for producing these multimetal oxides because it allows for careful control of film composition through the manipulation of precursor stoichiometry. Although it has been generally assumed that homogeneous precursor solutions yield homogeneous thin films, we recently reported evidence of nonuniform electron density profiles in aqueous-deposited films. Herein, we show that nonuniform electron densities in lanthanum zirconium oxide (LZO) thin films are the result of inhomogeneous distributions of metal components. Specifically, La aggregates at the film surface, whereas Zr is relatively evenly distributed throughout single-layer films. This inhomogeneous metal distribution persists in stacked multilayer films, resulting in La-rich interfaces between the sequentially deposited layers. Testing of metal-insulator-semiconductor devices fabricated from single and multilayer LZO films shows that multilayer films have higher dielectric constants, indicating that La-rich interfaces in multilayer films do not detrimentally impact film properties. We attribute the enhanced dielectric properties of multilayer films to greater condensation and densification relative to single-layer films, and these results suggest that multilayer films may be preferred for device applications despite the presence of layering artifacts.

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Multilayer model for determining the thickness and refractive index of sol–gel coatings via laser ellipsometry

Cited by 4 publications

References 20 publications

Non-uniform Composition Profiles in Inorganic Thin Films from Aqueous Solutions

Non-uniform Composition Profiles in Inorganic Thin Films from Aqueous Solutions

Same Precursor, Two Different Products: Comparing the Structural Evolution of In–Ga–O “Gel-Derived” Powders and Solution-Cast Films Using Pair Distribution Function Analysis

Nonuniform Composition Profiles in Amorphous Multimetal Oxide Thin Films Deposited from Aqueous Solution

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