Light scattering and roughness properties of optical components for 13.5 nm

Die stetige Reduzierung der Belichtungswellenlängen in der optischen Lithographie, motiviert durch die Herstellung immer kleinerer Halbleiterbauelemente, zieht enorme Herausforderungen an optische Komponenten nach sich. Insbesondere Streulicht an optischen Oberflächen stellt durch die starke Wellenlängenabhängigkeit gegenüber Oberflächenimperfektionen (~1/λ4) einen kritischen Faktor dar. Das Ziel dieser Arbeit besteht daher in der Untersuchung der Rauheits- und Streulichteigenschaften von Mo/Si Mehrschichtsystemen für die nächste geplante Lithographiewellenlänge 13,5 nm. Neben der Charakterisierung und Klassifizierung der wesentlichen Streulichtmechanismen wurden neue Lösungsstrategien erarbeitet, um Streulicht von Mehrschichtsystemen gezielt zu minimieren. Darüber hinaus wurde ein neuartiges Messverfahren entwickelt, welches basierend auf winkelaufgelösten Streulichtmessungen eine flächendeckende Charakterisierung der Oberflächenrauheit großer und komplex geformter EUV-Substrate ermöglicht. Somit können die Grenzen klassischer, hochauflösender Rauheitsmessverfahren, wie der Rasterkraftmikroskopie, überwunden werden, die aufgrund ihrer langen Messzeiten in der Regel nur für stichprobenartige Messungen geeignet sind. Im Zusammenspiel mit der Modellierung der Streulichteigenschaften des Mehrschichtsystems können so schon vor der Beschichtung Aussagen über den späteren EUV-Reflexionsgrad getroffen werden. Dadurch wird bereits früh im gesamten Herstellungsprozess eine zielgerichtete Optimierung möglich. Ein weiteres, sehr junges Forschungsfeld sind optische Komponenten für eine Wellenlänge von 6,x nm, die derzeit als nächste Lithographiewellenlänge nach 13,5 nm intensiv diskutiert wird. Um eine erste Abschätzung der Streulichteigenschaften und kritischen Rauheitsparameter zu ermöglichen, wird am Ende der Arbeit auch auf die Rauheitsentwicklung von Mehrschichtsystemen für diesen Wellenlängenbereich eingegangen

Advanced manufacturing techniques for X-ray and VHE gamma-ray astronomical mirrors.

The main theme of this thesis is on the development of the technologies for the future X-ray astronomy telescopes and specifically for the New Hard X-ray Mission and eROSITA (Spectrum-RG) missions. Other important next future X-ray missions, currently under advanced study and/or manufacturing are NuSTAR (USA), ASTRO-H (Japan) and GEMS (USA). The New Hard X-ray Mission (NHXM) is being developed in Italy as an evolution of the original HEXIT-SAT project and is now the hard x-ray project of reference for the Italian high energy community. NHXM is meant to provide a real breakthrough on a number of hot astrophysical issues, by exploiting the most advanced technology in broad-band (0.2 \u2013 80 keV) high angular resolution (<20 arc seconds HEW) grazing incidence mirrors and spectroscopic detectors, together with the use of a high efficiency imaging polarimeter. Such issues can be summarized in two main headings: \u25cf making the census of the population of black holes in the Universe and probing the physics of accretion in the most diverse conditions; \u25cf investigating the particle acceleration mechanisms at work in different contexts, and the effects of radiative transfer in highly magnetized plasmas and strong gravitational fields. These topics were identified as top priority in the study commissioned by the Italian Space Agency (ASI) in 2004 to the Italian scientific community with contracts involving Thales-Alenia Space Italy (TAS-I, Turin), the Media Lario Technologies (MLT, Lecco) company and the INAF institution. NHXM benefits from the phase A study of the canceled French-Italian-German SIMBOL-X mission (2007-2008) and has been recently subjected to a scientific phase B study financed by ASI. Media Lario Technologies company received a contract from ASI in 2009 for a Technology Development Program (ASI-TDP) aiming at improving the technology readiness level with also in-house adoption of hardware for the metrology/manufacturing of the multilayer x-ray optics. Spectrum-RG is a Russian - German x-ray astrophysical observatory scheduled for lunch in 2013. German Space Agency (DLR) is responsible for the development of the key mission instrument - the x-ray grazing incident mirror telescope eROSITA. The second experiment is ART-XC - an x-ray mirror telescope with a harder response than eROSITA, which is being developed by Russia (IKI, Moscow and VNIIEF, Sarov). The name eROSITA stands for extended Roentgen Survey with an Imaging Telescope Array. The general design of the eROSITA x-ray telescope is derived from that of ABRIXAS: a bundle of 7 mirror modules with short focal lengths make up a compact telescope which is ideal for survey observations. Similar designs had been proposed for the missions DUO and ROSITA but were not realized. Compared to those, however, the effective area in the soft x-ray band has now much increased by adding 27 additional outer mirror shells to the original 27 ones of each mirror module. The requirement on the on-axis resolution has also been confined, namely to 15 arc seconds HEW. For these reasons the prefix \u201cextended\u201d to the original name \u201cROSITA\u201d had been added. The scientific motivation for this extension is founded in the ambitious goal to detect about 100000 clusters of galaxies which trace the large scale structure of the Universe in space and time. The main scientific goals are: \u25cf to detect the hot intergalactic medium of 50-100 thousand galaxy clusters and groups and hot gas in filaments between clusters to map out the large scale structure in the Universe for the study of cosmic structure evolution; \u25cf to detect systematically all obscured accreting Black Holes in nearby galaxies and many (up to 3 Million) new, distant active galactic nuclei; \u25cf to study in detail the physics of galactic x-ray source populations, like pre-main sequence stars, supernova remnants and x-ray binaries. Max-Planck-Institute f\ufcr extraterrestrische Physik (MPE) is the scientific institute responsible for the eROSITA Payload. Media Lario Technologies (MLT) is the industrial enabler for the manufacturing of the Optical Payload for eROSITA - including the flight quality mandrels, and it is currently in the C/D Phase of the project. The research activity described in this thesis has been carried out at Media Lario Technologies company and at the Brera Astronomical Observatory under the supervision of INAF-OAB researchers Dott. Giovanni Pareschi and Dott. Gianpiero Tagliaferri. The research activity of the author of this thesis is focused on the development of an advance polishing technique for the mandrels to be used as masters in the mirrors replication by electroforming. The goal is to implement a process where the mandrels can be manufactured with a high accuracy (< 6 arc seconds HEW) and low roughness (< 0.2 nm rms) within a consistent short time. In the contest of the eROSITA and NHXM (projects currently running in MLT) the author participated as technical/scientific responsible, investigating innovative mandrels manufacturing technologies (e.g. Single Point Diamond Turning, shape corrective polishing) representing an evolution of the standard approach used so far. In this frame the author has also contributed to the adoption of a customized deterministic polishing machine and a customized 3D metrology device for the mandrel geometrical characterization. An additional research activity, performed by the author at Media Lario Technologies company and at the Brera Astronomical Observatory, is focused on the development of lightweight glass mirrors manufactured via cold-slumping technique for Imaging Atmospheric Cherenkov Telescopes (IACT). Very High Energy (VHE) gamma rays, with photon energies in the TeV range, can be detected by ground based experiments. In fact, such high energy photons interact high in the upper atmosphere and generate an air shower of secondary particles. These particles emit the so-called Cherenkov light, a faint blue light. The mirror elements here developed have a sandwich-like structure where the reflecting and backing facets are composed by glass sheets with an interposed honeycomb aluminum core. This effort found application at the world\u2019s largest IACT, the 17m MAGIC II telescope (currently operating in Roque de los Muchachos - La Palma, Canary Islands), where 112 mirrors (~ 1 squared meter each), manufactured with the newly developed cold-slumping technique here described, are installed

Design and Optimisation of Optical Metasurfaces Using Deep Learning

This thesis centres on the design, processing, and fabrication of tunable optical metamaterials. It incorporates physics-based simulation, deep learning (DL), and thin film fabrication techniques to offer a comprehensive exploration of the field of optical metamaterials. Placing stiff resonators on a flexible substrate is a common type of mechanically tunable metasurface, whose optical responses are tuned by dynamically adjusting the spacing between resonators by applying mechanical force. However, the significant modulus mismatch between materials causes stress concentration at the interface, leading to crack propagation and delamination at lower strain levels (20-50%), and limiting the optical tunability of the structure. To address this challenge, we propose two designs to manipulate stress distribution. Under mechanical force, the structure enables localised deformation, redirecting stress from critical areas. This mechanism minimises the accumulation of stress in the interface, thereby diminishing the risk of material failure and improving stretchability up to 120% compared to traditional designs. This extreme stretchability leads to a 143 nm resonance shift, which is almost twice as large as that of conventional geometry. A universal machine learning (ML)-based approach was developed to optimise the metasurface design across three key aspects: geometric parameters, material development, and free-form shape configuration. In design parameters optimisation, a fully connected neural network (FCNN) was developed with a mean absolute error (MAE) of 0.0051, recommending a single geometry with a 104 order of magnitude decrease in computational time when compared to finite element method (FEM) simulations used for data generation. The suggested structure provides extensive coverage of the colour space, encompassing 27.65% of the standard RGB (sRGB) space. For the materials development part, an inverse design (ID) network was combined with effective medium approximation (EMA), navigating infinite materials composition space to identify new compositions for custom applications. The last network was tasked to explore boundless free-form shape space to propose the one for the on-demand optical properties with MAE of 0.21. The accuracy of all networks was experimentally validated

Optical Studies of Ordered Monomolecular Layers: Ab Initio Simulation and Experiment

Due to the general interest on the alignment effect of the surface-bound ultrathin layers, this thesis presents research of the investigation of anchoring properties for liquid crystal (LC) molecules adsorbed on a solid substrate, using dual polarization interferometry (DPI). A new theoretical framework is designed based on the dual polarization interferometer for the detection of anisotropic information and the average anchoring angle of the adsorbed molecules, provided the liquid crystal bulk optogeometric parameters are well known. In the experiment, the nematic compound 4'-n-pentyl-4- cyanobiphenyl (5CB) is applied onto the silicon oxynitride surface, and a complete wetting monolayer with the average 56 ° polar angle and 16.6 Å thickness is observed in the stabilized stage. The results match quite well with the theoretical predictions in terms of the DPI phase change ratio. The thesis also extends the research into the functionalized substrate, in particular the Langmuir-Blodgett (LB) films covered substrate, which can give alignment effect to the deposited LC molecules. The LB forming molecule quinolinium tricyanoquinodimethanide (Q3CNQ) with long hydrocarbon chain (typically C18H37-Q3CNQ) is chosen. In order to justify the functionality of this material as an alignment layer, the electronic structure and the optical absorptive properties of this molecule in the LB phase are explored both in experiment and theory. Based on the very controversial history of this Q3CNQ compound, a robust computational LB model is built to examine the ground state, optimal geometry and the optical absorption features. A 530 nm absorption band is obtained to conclude the properties of the Q3CNQ LB layers, and also used to compare with our own experimental results

Simulation and implementation of moth-eye structures as a broadband anti-reflective layer

Conventional single layer thin anti-reflective coatings (ARCs) are only suitable for narrowband applications. A multilayer film stack is often employed for broadband applications. A coating of multiple layers with alternating low and high refractive index materials increases the overall cost of the system. This makes multilayer ARCs unsuitable for low-cost broadband applications. Since the discovery of moth-eye corneal nipple patterns and their potential applicability in the field of broadband ARCs, many studies have been carried out to fabricate these bio-inspired nanostructures with available manufacturing processes. Plasma etching processes used in microelectronic manufacturing are applied for creating these nanostructures at the Rochester Institute of Technology\u27s Semiconductor & Microsystems Fabrication Laboratory (SMFL). Atomic Force Microscope (AFM) scanned surfaces of the nanostructure layer are simulated and characterized for their optical properties using a Finite-Difference Time Domain (FDTD) simulator from Lumerical Solutions, Inc. known as FDTD Solutions. Simulation results show that the layer is anti-reflective over 50 to 350 nm broadband of wavelengths at 0° angle of incidence. These simulation results were supported by ellipsometer reflection measurements off the actual samples at multiple angles of light incidence, which show a 10% to 15% decrease in reflection for 240 to 400 nm wavelengths. Further improvements in the optical efficiency of these structures can be achieved through simulation-fabrication-characterization cycles performed for this project. The optimized nanostructures can then serve the purpose of low-cost anti-reflective coatings for solar cells and similar applications

Wave propagation and earth satellite radio emission studies

Radio propagation studies of the ionosphere using satellite radio beacons are described. The ionosphere is known as a dispersive, inhomogeneous, irregular and sometimes even nonlinear medium. After traversing through the ionosphere the radio signal bears signatures of these characteristics. A study of these signatures will be helpful in two areas: (1) It will assist in learning the behavior of the medium, in this case the ionosphere. (2) It will provide information of the kind of signal characteristics and statistics to be expected for communication and navigational satellite systems that use the similar geometry