Wire grid polarizers (WGPs), periodic nano-optical metasurfaces, are convenient polarizing elements for many optical applications. However, they are still inadequate in the deep ultraviolet spectral range. It is shown that to achieve high performance ultraviolet WGPs a material with large absolute value of the complex permittivity and extinction coefficient at the wavelength of interest has to be utilized. This requirement is compared to refractive index models considering intraband and interband absorption processes. It is elucidated why the extinction ratio of metallic WGPs intrinsically humble in the deep ultraviolet, whereas wide bandgap semiconductors are superior material candidates in this spectral range. To demonstrate this, the design, fabrication, and optical characterization of a titanium dioxide WGP are presented. At a wavelength of 193 nm an unprecedented extinction ratio of 384 and a transmittance of 10% is achieved.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/adom.201600250

Materials Pushing the Application Limits of Wire Grid Polarizers further into the Deep Ultraviolet Spectral Range

Several design-concepts are presented for so-called efficiency achromatized diffractive optical elements (EA-DOEs) possessing diffraction efficiency larger than 97% over a broad spectral range. We start with tracing two different methods for surface relief profiles well known from the literature: common depth and multilayer EA-DOEs. Successively we present the following new approaches together with design parameters and performance properties: 1) gradient-index EA DOEs, 2) sub-wavelength EA-DOEs, and 3) a so-called cut-and-paste strategy. All designs are based on scalar assumptions and certain necessary dispersion relations of two different materials. The scalar assumption is no real limitation as the minimum zone width of our main application, the correction of chromatic aberrations, is 50 -100 times the wavelength. From aforementioned relations, design parameters as profile heights are derived and the resulting diffraction efficiency can be deduced. Additionally it turns out that the necessary dispersion relation concerning the sub-wavelength EA-DOE is the same as for the common depth EA-DOE. Moreover, for the multilayer EA-DOE we were able to show that if the dispersion relations of the materials can be accurately described by a second order Cauchy series, the efficiency becomes generic and will be the same regardless of which materials are chosen. By proper choice of the materials, all types of EA-DOEs yield thicknesses of 10 - 30 µm which is more than ten times larger than for conventional DOEs. Due to the small refractive index difference of GRIN materials, such EA-DOEs exhibit thicknesses of 90 µm and more. Therefore, it is advisable to look for material combinations which yield thicknesses as small as possible.

/pdf/design-concepts-for-broadband-high-efficiency-does-50xhzi9qbw.pdf

Design concepts for broadband high-efficiency DOEs

Asymmetry properties of a periodic target on a substrate, such as a grating on a wafer, are determined. An inspection apparatus has a broadband illumination source with illumination beams point mirrored in the pupil plane of a high numerical aperture objective lens. The substrate and target are illuminated via the objective lens from a first direction and a second direction mirror reflected with respect to the plane of the substrate. A quad wedge optical device separately redirects diffraction orders of radiation scattered from the substrate and separates diffraction orders from illumination along each of the first and second directions. For example the zeroth and first orders are separated for each incident direction. After capture in multimode fibers, spectrometers are used to measure the intensity of the separately redirected diffraction orders as a function of wavelength.

Inspection Apparatus and Method, Lithographic Apparatus, Lithographic Processing Cell and Device Manufacturing Method

Approval: Committee Chair: ______________________________________ Program Director: ______________________________________ Dean, KGCOE: ______________________________________

/pdf/pupil-wavefront-manipulation-for-the-compensation-of-mask-h75j5rmfgh.pdf

Pupil wavefront manipulation for the compensation of mask topography effects in optical nanolithography

A method and tool for generating reconstructed images that model the high NA effects of a lithography tool used to image patterns produced by a mask. Comparison of the reconstructed images with reference images characterize the mask. The method involves providing a mask reticle for inspection. Generating matrix values associated with a high NA corrective filter matrix that characterizes a high NA lithography system used to print from the mask. Illuminating the mask to produce a patterned illumination beam that is filtered with filters associated with the high NA corrective filter matrix elements to obtain a plurality of filtered beams that include raw image data that is processed to obtain a reconstructed image that is further processed and compared with reference images to obtain mask characterization information.

Photomask inspection and verification by lithography image reconstruction using imaging pupil filters

A reflective X-ray microscope for examining an object in a object plane, when the object is illuminated by radiation at a wavelength of less than 100 nm, especially less than 30 nm. The microscope comprises a second subsystem arranged after the first subsystem in the beam path, and which has at least one third mirror (S3). Independent claims are also included for: (1) an inspection system for examining objects, especially masks for microlithography; (2) a method for inspection of objects, especially masks for microlithography; and (3) application of an inspection system.

Reflective X-ray microscope e.g. for microlithography, includes additional subsystem arranged after first subsystem along beam path and containing third mirror

The invention relates to a reflective X-ray microscope for examining an object on an object plane wherein the object is illuminated with radiation at a wavelength of < 100 nm, especially < 30 nm, and imaged in an enlarged form on an image plane, comprising a first sub-system which is arranged in the path of radiation from the object plane to the image plane and comprises a first mirror and a second mirror.The invention is characterized in that the reflective X-ray microscope has a second sub-system which is arranged downstream from the first sub-system in the path of radiation and which comprises a third mirror.

Reflective x-ray microscope and inspection system for examining objects with wavelengths of≤ 100nm

A first subsystem with a first concave mirror (S1) and a second convex mirror (S2) both centered on an optical axis (HA) fits in a beam path from an object plane to an image plane and has a first optical element for wavelengths less than 30 nm. A first image (Z) is formed in a first-image plane (2). A second subsystem fits in a beam path after the first image. Independent claims are also included for the following: (a) An inspection system for examining objects, e.g. masks for microlithography with wavelengths less than 100 nm, preferably less than 30 nm; (b) A method for inspecting objects, e.g. masks for microlithography with wavelengths less than 100 nm.

Reflective X-ray microscope for examining an object in an object plane illuminates the object with beam wavelengths less than 30 nm while scanning it into an image plane as an enlarged object

The invention relates to a method and an apparatus for measuring masks for photolithography. In this case, structures to be measured on the mask on a movable mask carrier are illuminated and imaged as an aerial image onto a detector, the illumination being set in a manner corresponding to the illumination in a photolithography scanner during a wafer exposure. A selection of positions at which the structures to be measured are situated on the mask is predetermined, and the positions on the mask in the selection are successively brought to the focus of an imaging optical system, where they are illuminated and in each case imaged as a magnified aerial image onto a detector, and the aerial images are subsequently stored. The structure properties of the structures are then analyzed by means of predetermined evaluation algorithms. The accuracy of the setting of the positions and of the determination of structure properties is increased in this case.

Method and apparatus for measuring of masks for the photo-lithography

Immersion lithography offers the semiconductor industry the opportunity to extend current ArF processes before switching to shorter wavelengths. As numerical apertures of scanners for hyper NA move above 1.0 with immersion lithography, increased attention must be paid to the photomask or reticle and its wafer printability. Feature sizes on the photomask become increasingly critical as they behave more like partial wire grid polarisers, as they become comparable to, or smaller than the wavelength. Besides challenges to address reticle polarisation effects, lithographers must also consider the polarisation state of the illumination and subsequently the contrast loss for light with a TM polarisation state. Such an effect, also called the vector effect, is caused by the increasing angle of incidence of the diffracted light for larger numerical apertures on the scanner. Therefore, for wafer printing using hyper NA scanners, the industry consensus is that TE polarised illumination must be used to meet the stringent requirements of imaging contrast. In this paper, initial results of measurements using the optical test stand and the alpha tool of a completely new AIMS™ 1 tool for the 45nm node will be presented. The system covers all aspects of immersion and polarisation lithographic emulation. Measurements have been made on binary and phase shift masks with different sizes of features and on programmed defects.

Axel Zibold

Papers

Reflective X-ray microscope e.g. for microlithography, includes additional subsystem arranged after first subsystem along beam path and containing third mirror

Reflective x-ray microscope and inspection system for examining objects with wavelengths of≤ 100nm

Reflective X-ray microscope for examining an object in an object plane illuminates the object with beam wavelengths less than 30 nm while scanning it into an image plane as an enlarged object

Method and apparatus for measuring of masks for the photo-lithography

First results for hyper NA scanner emulation from AIMS 45-193i