Overview of variable-angle spectroscopic ellipsometry (VASE): II. Advanced applications

Johs, B.; Woollam, John A.; Herzinger, C. M.; Hilfiker, James N.; Synowicki, R. A.; Bungay, Corey

doi:10.1117/12.351667

Cited by 114 publications

(104 citation statements)

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“…The ellipsometer is installed at the deposition chamber which is equipped with fused silica windows at angle of light incidence of 70.7° with respect to the surface normal. The spectra of conventional spectroscopic ellipsometry (SE) parameters (Ψ, ∆) [15] within the probing photon energy range of 1.2-3.3 eV were regularly recorded at 6 s intervals. The data were acquired and evaluated by the WVASE ® software.…”

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confidence: 99%

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Real-time evolution of the indium tin oxide film properties and structure during annealing in vacuum

Rogozin

Shevchenko

Vinnichenko

et al. 2004

Applied Physics Letters

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Indium tin oxide (ITO) is widely applied as a transparent conductive oxide coating. A standard and successful industrial route of production is its deposition by magnetron sputtering from a compound (oxide) target [1]. To increase cost efficiency, it would be preferable to sputter reactively from a metal target at sufficiently high partial pressure of oxygen. However, under this condition, a satisfactorily low resistivity of the films cannot readily be obtained, [2] so that a deposition on heated substrates or post-deposition annealing is necessary. So far, the annealing processes for reactively sputtered ITO [3,4] have only been studied for metal-rich films, in contrast to comprehensive studies after magnetron sputtering from ceramic targets [5][6][7][8][9][10]. Moreover, mainly isothermal heat treatment is considered in the literature, although annealing using a temperature ramp is of more relevance for practical application. Several investigations report on real-time in situ monitoring of the ITO film resistivity and reflectivity [9,10], which is used for an indirect characterization of the crystalline structure of the films. This approach requires simplifying assumptions on the linear dependence of the resistivity or reflectivity on the crystalline fraction, and the stability of the film roughness during annealing. Direct investigations of the influence of heat treatment on the ITO film structure are so far limited to post-annealing studies by X-ray diffraction (XRD) and scanning or transmission electron microscopy [3][4][5]7,8,11].Annealing of ITO is known to be very efficient in increasing the carrier concentration. It can be quite reasonably explained by the FrankKöstlin model [12] which accounts for tin donor activation at elevated temperatures. However, this model is valid only for crystalline ITO. The amorphous-to-crystalline transition in ITO during annealing is often assumed as the reason for this activation, but the physics behind the experimental observation is not clear. In the present letter we report the results of a real-time in situ investigation of the film properties and the structure evolution during annealing in vacuum.The films are produced by reactive pulsed middle frequency magnetron sputtering using the facility and procedure described in Ref. 13. The chamber was pumped to a base pressure of 4 × 10 -4 Pa before deposition. The deposition runs were carried out for 2.5 min at an Ar flow of 30 sccm (partial pressure 1.2 Pa) and O 2 flow of 64 sccm (0.3 Pa). The films are grown on Si (100) substrates (24 × 12 × 0.3 mm 3 ) covered with SiO 2 (510 nm), which were not heated externally during deposition. The average thickness of the deposited films is 130 nm. The as-deposited films show no crystalline peaks in the XRD patterns and are considered as amorphous.The post-deposition annealing of identical ITO samples was carried out at two different experimental setups, the ROssendorf Beam Line (ROBL) at the European Synchrotron Radiation Facility in Grenoble, [14] and the ITO deposition facility ...

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“…The dielectric function of the surface roughness layer was modeled as a 50/50 vol.% mixture of the ITO layer and voids, applying the Bruggeman effective medium approximation (EMA). The dielectric function of bulk ITO was parameterized in the Drude-Lorentz approach [15], which allows estimation of the free electron density N Dr at a given temperature [16].…”

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confidence: 99%

Real-time evolution of the indium tin oxide film properties and structure during annealing in vacuum

Rogozin

Shevchenko

Vinnichenko

et al. 2004

Applied Physics Letters

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“…Numerous material parameters can be extracted, including layer thickness, surface and/or interfacial roughness, optical constants, and void fraction. [9][10][11] In this work, data were analyzed assuming that the films were dense, smooth, and homogeneous, but uniaxially anisotropic.…”

Section: Discussionmentioning

confidence: 99%

Vacuum ultraviolet optical analysis of spin‐cast chitosan films modified by succinic anhydride and glycidyl phenyl ether

Nosal¹,

Thompson²,

Tiwald³

et al. 2007

Surface & Interface Analysis

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Optical properties of spin‐cast chitosan films were determined in the vacuum ultraviolet (VUV) through visible regions of the spectrum using spectroscopic ellipsometry. The onset of absorption in the ultraviolet was determined for chitosan films modified with succinic anhydride (SA) and glycidyl phenyl ether (GPE). This absorption was accounted for by including Gaussian and Tauc–Lorentz shaped oscillators in the optical model. VUV through visible optical constants were determined for these modified films, as well as for immunoglobulin G (IgG) attached to GPE‐modified samples. Several resonant oscillator structures exhibit greatly differing oscillator parameters for the as‐deposited, as well as SA‐ and GPE‐modified films. These in‐plane and out‐of‐plane oscillator strengths, energy positions, and broadening were determined and tabulated, and their chemical origins identified. A phenyl resonant π‐bond at approximately 6.3 eV was observed for the GPE‐modified sample. This was not present in the bare chitosan data. GPE contains a phenyl group in the molecule and absorption due to it is clearly identified. Clarity of data after surface chemical modification is due to the high surface sensitivity of VUV ellipsometry. Copyright © 2007 John Wiley & Sons, Ltd.

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“…This is important because very accurate measurements of ⌬ are required for adequate characterization of unknown samples. 29 …”

Section: Methodsmentioning

confidence: 99%

Characterization of porous low-k films using variable angle spectroscopic ellipsometry

Othman

Lubguban

et al. 2006

Journal of Applied Physics

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Variable angle spectroscopic ellipsometry ͑VASE™͒ is used as a tool to characterize properties such as optical constant, thickness, refractive index depth profile, and pore volume fraction of single and bilayer porous low-k films. The porous films were prepared using sacrificial pore generator ͑porogen͒ approach. Two sets of porous films with open-and closed-pore geometries were measured. Three models were used for data analysis: Cauchy, Bruggeman effective medium approximation ͑BEMA͒, and graded layer. Cauchy, a well-known model for transparent films, was used to obtain thickness and optical constant, whereas BEMA was utilized to calculate the pore volume fraction from the ellipsometric data. The Cauchy or BEMA models were then modified as graded layers, resulting in a better fit and a better understanding of the porous film. The depth profile of the porous film implied a more porous layer at the substrate-film interface. We found 3%-4% more porosity at the interface compared with the bulk for both films. This work shows that VASE™, a nondestructive measurement tool, can be used to characterize single-and multigraded layer porous films quickly and effectively.

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Overview of variable-angle spectroscopic ellipsometry (VASE): II. Advanced applications

Cited by 114 publications

References 0 publications

Real-time evolution of the indium tin oxide film properties and structure during annealing in vacuum

Real-time evolution of the indium tin oxide film properties and structure during annealing in vacuum

Vacuum ultraviolet optical analysis of spin‐cast chitosan films modified by succinic anhydride and glycidyl phenyl ether

Characterization of porous low-k films using variable angle spectroscopic ellipsometry

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