Optical interference coatings measurement problem 2019 [Invited].

The 2019 Optical Interference Coatings measurement problem comprised the determination of the total backscattering, forward scattering, reflectance, and transmittance spectra of a multilayer system.

Structured Mo/Si multilayers for IR-suppression in laser-produced EUV light sources.

Laser produced plasma sources are considered attractive for high-volume extreme-ultraviolet (EUV) lithography because of their high power at the target wavelength 13.5 nm. However, besides the required EUV light, a large amount of infrared (IR) light from the CO drive laser is scattered and reflected from the plasma as well as from the EUV mirrors in the optical system.

Spectral angle resolved scattering of thin film coatings.

The light scattering of interference coatings is strongly dependent on the wavelength. In addition to the general strong increase of scattering as the wavelengths get shorter, dramatic scatter effects in and around the resonance regions can occur. This is discussed in detail for highly reflective and chirped mirrors.

Optical interference coatings measurement problem 2013 [invited].

The 2013 Measurement Problem comprised the determination of the reflectance of a broadband antireflection (AR) coating in the spectral region from 400 to 700 nm at near 0° angle of incidence.

Characterization of optical coatings using a multisource table-top scatterometer.

Light scattering measurement and analysis is a powerful tool for the characterization of optical and nonoptical surfaces. To enable a more comprehensive postmeasurement characterization, three visible laser sources were recently implemented in a highly sensitive table-top scatterometer with 3D spherical detection capability. Based on wavelength scaling, the instrument is utilized to characterize thin-film coatings and their substrates with respect to surface roughness, roughness growth, and contamination.

Scattering reduction through oblique multilayer deposition.

Scattering from multilayer coatings depends on the roughness of each interface as well as their cross-correlation properties. By depositing thin film coatings under oblique incidence, the cross-correlation properties can be specifically adapted and consequently also the scattering characteristics. This will be illustrated for Mo/Si multilayers, for which a scattering reduction of more than 30% can be achieved.

Evaluation of subsurface damage by light scattering techniques.

Subsurface damage (SSD) in optical components is almost unavoidably caused by mechanical forces involved during grinding and polishing and can be a limiting factor, in particular for applications that require high laser powers or an extreme material strength. In this paper, we report on the characterization of SSD in ground and polished optical surfaces, using different light scattering measurement techniques in the visible and extreme ultraviolet spectral ranges. The materials investigated include fused silica, borosilicate glass, and calcium fluoride.

Comprehensive nanostructure and defect analysis using a simple 3D light-scatter sensor.

Light scattering measurement and analysis is a powerful tool for the characterization of optical and nonoptical surfaces. A new 3D scatter measurement system based on a detector matrix is presented. A compact light-scatter sensor is used to characterize the scattering and nanostructures of surfaces and to identify the origins of anisotropic scattering features.

Modeling of light scattering in different regimes of surface roughness.

The light scattering of rough metallic surfaces with roughness levels ranging from a few to several hundred nanometers is modeled and compared to experimental data. Different modeling approaches such as the classical Rayleigh-Rice vector perturbation theory and the new Generalized Harvey-Shack theory are used and critically assessed with respect to ranges of validity, accuracy, and practicability. Based on theoretical calculations and comparisons with Rigorous Coupled Wave Analysis for sinusoidal phase gratings, it is demonstrated that the approximate scatter models yield surprisingly accurate results and at the same time provide insight into light scattering phenomena.

Instrument for close-to-process light scatter measurements of thin film coatings and substrates.

Scatter analysis is an effective method for the characterization of thin film components. The new highly sensitive table top system ALBATROSS-TT (3D-Arrangement for Laser Based Transmittance, Reflectance and Optical Scatter Measurement-Table Top) has been developed at the Fraunhofer Institute in Jena to meet the specific requirements for close-to-process applications. Extremely high sensitivity with a noise equivalent angle resolved scatter level of 2×10(-8) sr(-1), full three-dimensional spherical measurement capability, and an instrument size as small as 0.

Definition of roughness structures for superhydrophobic and hydrophilic optical coatings on glass.

With specific modeling, measurement, and analysis procedures, it is possible to predict, define, and control roughness structures for tailored wetting properties of optical coatings. Examples are given for superhydrophobic and hydrophilic sol-gel layers on glass substrate.

Optical Interference Coatings 2010 Measurement Problem.

The 2010 Measurement Problem comprised the determination of the reflectance of high-reflective dielectric mirrors at 1064 nm.

Angle-resolved scattering: an effective method for characterizing thin-film coatings.

Light scattered from interface imperfections carries valuable information about its origins. For single surfaces, light-scattering techniques have become a powerful tool for the characterization of surface roughness. For thin-film coatings, however, solving the inverse scattering problem seemed to be impossible because of the large number of parameters involved.

Influence of the substrate finish and thin film roughness on the optical performance of Mo/Si multilayers.

Scattering resulting from interface imperfections critically affects the image contrast and optical throughput of multilayer coatings for 13.5 nm. To investigate the scattering mechanisms, at-wavelength scattering measurements in combination with atomic force microscopy are analyzed for an in-depth characterization of the roughness properties.

Angle-resolved scattering and reflectance of extreme-ultraviolet multilayer coatings: measurement and analysis.

Roughness-induced light scattering critically affects the performance of optical components, in particular at short wavelengths. We present a stand-alone instrument for angle-resolved scattering and reflectance measurements at 13.5 nm in the extreme-ultraviolet (EUV) spectral range.

Extreme-ultraviolet-induced oxidation of Mo/Si multilayers.

The extreme-ultraviolet (EUV)-induced oxidation of Mo/Si multilayer mirrors was characterized by several methods: EUV reflectivity, x-ray photoelectron spectroscopy, small-angle x-ray reflectometry, atomic force microscopy, and EUV scattering measurements. Based on the results of the different investigation techniques, an oxidation model was developed to explain the degradation of the mirrors under EUV radiation.

Roughness evolution and scatter losses of multilayers for 193 nm optics.

Optical scattering arising from interface roughness and interference effects is a dominant loss mechanism of thin film coatings for 193 nm. A procedure is presented where at-wavelength scatter measurements in combination with atomic force microscopy are used as a tool for the in-depth characterization of the origins of scattering. For highly reflective coatings, the influence of the substrate roughness on the growth properties is analyzed.

Optical interference coatings 2007 measurement problem.

The 2007 Measurement Problem comprised measurements of the transmission and reflectance spectra and the determination of optical constants for a single oxide layer on fused silica. The angle of incidence was 45 degrees .

EUV reflectance and scattering of Mo/Si multilayers on differently polished substrates.

Highly reflective Molybdenum/Silicon multilayer mirrors for 13.5 nm are characterized at-wavelength using a new laboratory size measurement system for EUV reflectance and scattering. Roughness analysis before and after coating by Atomic Force Microscopy indicates roughness enhancement as well as smoothing effects during thin film growth.

Bulk scattering properties of synthetic fused silica at 193 nm.

The bulk scattering of synthetic fused silica for 193 nm lithography was investigated using an instrument for high-sensitive total and angle resolved scattering measurements at 193 nm. Bulk scattering coefficients alpha between 0.6x10(-3) and 1.

Design and characterization of nanostructured ultrahydrophobic coatings.

Films with specific nanoroughness were designed by "virtual coating" to yield ultrahydrophobicity while the light scatter remained below an application-relevant threshold. Examples of coating experiments demonstrate the realization of predicted properties.

Measurement system to determine the total and angle-resolved light scattering of optical components in the deep-ultraviolet and vacuum-ultraviolet spectral regions.

An instrumentation for total and angle-resolved scattering (ARS) at 193 and 157 nm has been developed at the Fraunhofer Institute in Jena to meet the severe requirements for scattering analysis of deep- and vacuum-ultraviolet optical components. Extremely low backscattering levels of 10(-6) for the total scattering measurements and more than 9 orders of magnitude dynamic range for ARS have been accomplished. Examples of application extend from the control of at-wavelength scattering losses of superpolished substrates with rms roughness as small as 0.

Effects of interface roughness on the spectral properties of thin films and multilayers.

We introduce two parameters, large-scale and small-scale rms roughness, to take into account the interface properties of thin films and multilayers in the calculation of their specular reflectance and transmittance. A theoretical motivation for the introduction of these two parameters instead of a standard single rms roughness is provided. Experimental power spectral density functions of several samples are used to illustrate ways in which the parameters introduced can be evaluated.

Optical coatings with enhanced roughness for ultrahydrophobic, low-scatter applications.

Optical coatings with enhanced roughness offer promising prospects for ultrahydrophobic transparent surfaces with controlled scatter losses. Our approach links roughness characteristics with both wetting behavior and scattering. Experiments with rough oxide layers yielded surfaces with a high water contact angle.

Light-scattering measurements of optical thin-film components at 157 and 193 nm.

An instrument for total backscattering and forward-scattering measurements of optical coating components at 157 and 193 nm is described. The system is operated in both vacuum and nitrogen purge gas. An excimer laser as well as a deuterium lamp can be used as a radiation source.