The main challenge in developing a suitable EUV photoresist, particularly for high Numerical Aperture (NA) EUV lithography anticipated for late 2024, lies in the Resolution, Line Width Roughness, and Sensitivity (RLS) trade-off. PiBond has been actively addressing this challenge by developing silicon photoresist (SiPR) based on chemically modified HSQ siloxane chemistry, consisting of a single polymer component. This resist, a non-metal negative tone, high Si-containing, employs the industry-standard TMAH developer. Previously, we achieved a resolution of 32nm pitch with a dose of 170mJ/cm2 and a Line Width Roughness (LWR) of 5.3nm. In this study, we synthesized a novel chemically modified HSQ-type siloxane resist to enhance RLS characteristics, assessing its performance using both Electron Beam Lithography (EBL) and EUVL. Utilizing the EUV Interference Lithography tool at PSI, we obtained a 28nm pitch resolution with an improved LWR of approximately 3.2nm, while controlling the dose-to-size to about 120mJ/cm2. Furthermore, by employing a suitable silicon hard mask underlayer developed in-house, we further enhanced sensitivity by 24% at 28nm pitch and 38% at 30nm pitch resolution. Crucially, we established correlations between EBL and EUV for our SiPR, leveraging the accessibility of EBL compared to EUV tools. Leveraging these correlations, we effectively utilized EBL to investigate the newly synthesized resist and optimize processing conditions. Our findings demonstrate the significant impact of both resist functionalization and processing conditions on the final lithography performance.
Extended reality (XR) technologies that enhance and replace our view of the world are vividly moving towards mainstream as supporting professional and consumer applications approach commerciality. Majority of devices that are enabling XR content heavily rely on optics. However, making optics good enough to meet demanding user expectations remains difficult in terms of optical quality, cost, throughput and even in a sustainable point of view. Additive manufacturing processes are readily adopted in XR optics helping close the difficulty gap. This presentation covers new additive processed materials for XR devices related optics with their possibilities and challenges.
The article gives two examples of the incorporation of liquid phase coated low refractive index (RI) and high refractive index materials in a proof-of-concept optical devices. Using ultra low RI (1.25) and ultra high RI (2.05), a 12-layer dielectric mirror is constructed. Optical properties of the stack are compared against to simulations, and a SEM-image of the stack is provided. The second example of using of high RI/low RI materials is provided where UV-curable, high RI material (1.9) nanoimprint material is nanopatterned, followed by gap-fill and protections by a cover glass using a dual cure (UV+thermal) RI 1.4 low refractive index bonding adhesive.
The RLS trade-off of EUV resists has been a major technical issue for high-volume manufacturing using EUVL. Significant attempts to develop of chemically-amplified resists, metal-containing resists, and a variety of other material classes have been made to obtain low LER at high resolution (R) and at a reasonable sensitivity (S). Previously, we have developed and reported work on silanol-containing polyhydrogensilsesquioxane resins and their use as negative tone resists. The developed silanol-containing polymer resists have demonstrated enhanced EUV sensitivity compared to traditional hydrogen silsesquioxane resins, and at the same time maintaining excellent etch properties. The resist may enable a bilayer stack technology in EUVL. Herein we report novel functionalized polyhydrogensilsesquioxane polymers and their use as negative tone resists. These materials exhibit improved LER/LWR and reasonably good EUV sensitivity. In best cases, data suggests no residues or bridging in the non-exposed areas. The optimized resist exhibits sub-20nm halfpitch resolution, low LER (2-3nm), and reasonable sensitivity (82.5 mJ/cm2). In addition, we also investigated the effect of three organic underlayers for EUV patterning and compared with the silicon substrate.
KEYWORDS: Extreme ultraviolet lithography, Etching, Extreme ultraviolet, Electron beam lithography, System on a chip, Coating, Silicon, Line edge roughness, Metals, Line width roughness
Extreme ultraviolet lithography (EUVL, λ = 13.5 nm) is the most promising candidate to pattern the finest features in the next-generation integrated circuit manufacturing. Chemically-amplified resists (CARs) have long been used as state-of-the art photoresists and have been considered as EUV resist. Recently, inorganic and metal-containing resist materials have received significant attention in both academia and industry areas, with the aim to improve the resist performance in terms of resist resolution (R), line-edge roughness (LER), and sensitivity (S) to solve the well-known RLS trade-off. However, the resists reported to date usually have either problem in terms of RLS trade-off or pose metal contamination, which is a serious issue in expensive EUV equipment. Differently, in this report, we demonstrate our recent success in the development of the photochemistry of silicon compounds and resist formulations to obtain novel EUV negative tone resists with high resolution (up to 22nm pitch line/space patterns), low line-edge roughness (1-3nm) with reasonable EUV sensitivity. We also discuss their high etch selectivity to a PiBond’s SOC organic underlayer, which enable a bilayer lithography stack for EUVL patterning. Their excellent etch performances by RIE plasma is also reported.
Continuously increasing performance requirements in CMOS image sensor based digital camera devices demand
significant improvement of the optical part of the device as well as improved endurance to camera module assembly.
Optical structures construction is the key element to improve the device efficiency and sensitivity. This is especially true
for the small pixel size sensors used for mobile phone applications, wherein pitch size is reduced to integrate more pixels
on the same area of semiconductor surface. Traditionally, the optical stack is based on organic photo-resist like materials.
The introduction of inorganic Spin On Dielectric (SOD) materials opens several new options. Two novel applications of
these materials are presented in this paper. In the first one, a waveguide is formed in the device backend and filled with
high refractive index SOD (RI=1.652 @ 650nm) to improve optical performance. The second one employs a low
refractive index SOD (RI~1.4 @650nm) topcoat, which enables easier micro lens engineering and optimization, and
further offers advantage of organic micro lens mechanical protection. The two integration schemes are presented along
with SOD material characteristics and processing details.
In this study, the sol-gel process to fabricate directly UV-photopatternable lanthanum-doped lead zirconate titanate (PLZT) films was investigated. Photosensitive films were obtained via chemical methacrylic acid modification of metal organic PLZT precursors. Spin-on deposited films were patterned using direct UV-photolithography process. Patterned films were annealed in air, in order to obtain perovskite type crystalline material. AFM and XRD techniques were used for the characterization of the material and fabricated structures. The sol-gel processed PLZT films had good crystallinity, they were crack-free, and had low surface roughness. The films exhibit electro-optic effect being therefore interesting to be used in active integrated optic devices.
We report on the fabrication of transparent, conductive and directly photopatternable, pure and Sb-doped tin dioxide thin films. Precursors used were antimony(III)isopropoxide and a photo-reactive tin alkoxide synthesized from tin(IV)isopropoxide and methacrylic acid. The synthesis of methacrylic acid modified tin alkoxide was monitored in-situ using IR- and ESI-TOF mass spectroscopic techniques. Sb-doped organo-tin films were deposited via single layer spin coating. After deposition the films were patterned via photopolymerization, using a mercury I-line UV-lamp. All investigated materials could be patterned with 3 μm features. After development in isopropanol, the films were annealed in air, in order to obtain crystalline and conductive films. The electrical conductivities of the annealed thin films with, and without, UV-irradiation were determined using a linear four-point method. The direct photopatterning process was found to increase the film conductivity for all the Sb-doping levels tested. The mechanisms for the increased conductivity were characterized using AFM, XPS and XRD techniques.
This paper introduces the usage of directly UV-photopatternable sol-gel based materials and the processing methods for the fabrication of binary diffractive optical elements. We designed and modeled a binary axicon - an optical element, which produces almost diffraction free beam in a specified distance from the element. We fabricated sol-gel based hybrid-glass materials and tailored their processing parameters to fit the demands of the axicon design. Resolution of 2 microns, film thickness of 850 nm, and certain morphological properties were required. The materials were derived from zirconium(IV)isopropoxide, methacrylic acid, and methacryloxypropyltritethoxysilane. We determined the morphological and line quality of the fabricated axicons as a function of the UV-irradiation dose. In addition, we measured the optical characteristics of the axicons in terms of the axial and radial intensity profiles. The reasons for the differences between calculated and measured values are discussed.
KEYWORDS: Transmitters, Sensors, Monte Carlo methods, Scattering, Receivers, Vertical cavity surface emitting lasers, Computer simulations, Diffraction, Ray tracing, Data modeling
Hybrid glass materials are used in the photolithographic fabrication of optical and opto-mechanical structures. Two different methods are introduced. The first one is referred as photolithographic patterning and the other as direct photolithographic deforming of hybrid glass materials. Fabrication of isolated lenslets, lens arrays, gratings and other binary structures is presented. The hybrid glass material used in the photolithographic patterning features a maximum spectral extinction coefficient of 2.0 X 10-4 micrometers -1 between 450 nm and 1,600 nm and a refractive index of 1.53 at 632.8 nm. The fabricated structures feature large convex lens sags (up to 100 microns) with rms surface roughness values ranging from 10 to 45 nm, when the photolithographic patterning is applied. The hybrid glass material used in the direct photolithographic deforming exhibits a maximum spectral extinction coefficient of 1.6 X 10-3 micrometers -1 at wavelengths ranging from 450 nm to 2200 nm and a refractive index of 1.52 at 632.8 nm. The fabricated structures exhibit rms surface roughness between 1 and 5 nm, when direct photolithographic deforming is applied. These materials and methods are highly promising for micro- optics fabrication.
We present the design and fabrication of miniaturized light sources for micro-optical systems using organic light emitting diodes (OLEDs). These devices can be integrated on a micro-optical table (MOT) using various backplanes. Acceptable angular uniformity of emitted radiance, and a brightness of more than 30,000 cd/m2 can be readily achieved with OLEDs having areas ranging from 0.0004 cm2 to 0.0363 cm2.
Liquid phase deposition of sol-gel method derived hybrid glass materials is utilized for fabrication of UV light deformable thin films. The hybrid glass material undergoes a surface-relief deformation when exposed to UV light. The observed deformation phenomenon is in the form of a physical expansion of the exposed areas. The maximum deformation when the material was patterned as a sinusoidal grating was 643 nm. The hybrid glass material features an index of refraction of 1.52, rms surface roughness of 2.25 +/- 0.83 nm after processing, and extinction coefficients of 1.2 10-3 micrometers -1 and 0.47 10-3 micrometers -1 at wavelengths of 633 nm and 1550 nm, respectively.
We have used non-sequential ray tracing as a simulation tool to model micro-optical systems. Ray tracing can be used to model micro-optical systems as long as the wave nature of the light is not dominant. Non-sequential ray tracing takes inherently into account the aberrations of the optical system and enables the modeling of scattering and stray light effects. We have used measured scattering properties of a hybrid-glass lens material to model scattering in an example imaging micro-optical system. We have also used non-sequential ray tracing to model a straight and a bent light-guide that can be used as chemical sensors. Modeling estimates the amount of light going through the optical system to the detector and shows the paths of the rays leaking out from the system.
The transient and steady state performance of organic light- emitting devices (OLEDs) has been investigated with a view towards suitability for pulse sources. The rise and fall times of the electroluminescence of the different structures and materials were afforded special attention. The tested devices cover single and multi-layer structures with different layer thicknesses. Both molecular and polymeric- based devices were tested. Molecular materials used in the OLEDs were N, N'-bis(3-methylphenyl)-N,N'-diphenylbenzidine (TPD) as a hole transporter, tris-(8-hydroxyquinolate) aluminum (Alq3) as an electron transporter/emitter and 4,7-diphenyl-1,10-phenanthroline (BCP) as a hole blocking material. Poly)2-methoxy, 5-(2'-ethyl-hexoxy)-1,4- phenylene-vinylene) (MEH-PPV) and poly(3,4- ethylenedioxythiophene)/poly(styrene) (PEDOT/PSS) were the polymeric materials used in the devices. The effect of the driving voltage on the response time and the current density in transients was under investigation. In addition, changes in the response time were studied, when the bias voltage was applied.
The paper reports on methods to fabricate novel materials and associated processing for optoelectronics and optical structures compatible with manufacturing of microsystems. Furthermore, the paper presents results on designing, fabrication and packaging of different modules and microsystems for sensor, instrumentation and optical communication applications. New materials are developed and liquid phase deposition methods are applied for the fabrication of lithography compatible glasses, conducive transparent glasses and protective materials. The developed lithographic glasses are used for example to fabricate micro-opto-mechanical structures. By using these materials and structures, a miniaturized micro-optical table is constructed. Furthermore, organic and hybrid semiconductors and light emitting materials are manufactured and their integration as micro-optical components and systems are described. From the view-point of module integration, a wavelength tunable laser diode, i.e., a MOEMS consisting of laser diode and a silicon micromachined Fabry-Perot interferometer, is demonstrated and modeled. A ~4nm wavelength tuning range with ~0.3nm FWHM spectral width is experimentally obtained at 980 nm. Moreover, the use of a passive alignment structure for the fiber pigtailing of a multimode laser diode is demonstrated. The ceramic alignment structure is hot embossed with a LIGA machined tool and results in a ~56% coupling efficiency, corresponding to the theoretical maximum.
Sol-gel processing consists several variable parameters during materials synthesis and post processing steps. The sol-gel synthesis is rather sensitive for the parameters such as pH, temperature, type of catalyst, reaction time etc. However, this sensitivity can be taken as an advantage when developing and studying new materials and their properties. Furthermore, since the sol-gel technology mainly describes the fabrication of solid state materials from a liquid phase by applying metal alkoxides or metal salts as precursors, the post processing such as sintering has critical effects on the final form and properties of the solid material. Combinatorial chemistry and methods are valuable tools to estimate the effects of different variables and to build-up combinatorial libraries for the sol-gel technique. This paper generally describes potentials and the usage motivation of combinatorial chemistry in the sol-gel technology by taking into account some major steps in the synthesis and processing which are valuable for the estimation of the final product properties. Different kind of post processing steps in the combinatorial manner are studied in details. As an example the post processing of sol-gel derived semiconductor oxides and photosensitivity of hybrid sol-gel glasses are presented. The combinatorial treatment and measurement methods for these materials are explained.
Coumarin molecules are widely used as laser dyes and their luminescence properties show a large potential for their use as light emitters in organic light emitting devices. These molecules however are lacking of photo, chemical and thermal stability. At the outset, the fact that when the coumarin or other organic active molecules are covalently bonded to a metal oxide host, the stability properties can be improved. In this paper we outline the synthesis of several different coumarin-3-carboxylic acids by using a one-pot synthesis from dipotassium o-methoxybenzylidenemalonates. We also outline a preparative route for the synthesis of corresponding coumarin-3-carboxylic amides with a side chain containing terminal trimethyoxysilane functionality, which allows the creation of a covalent bond between the molecule and a silicon oxide host matrix. These silylated coumarins are then covalently bonded through a sol-gel method to a developing siloxane host matrix. The silicon matrix materials have been synthesized through hydrolysis and simultaneous condensation of metalalkoxides such as phenylmethyltrimethoxysilane. Coumarin dyes are bonded in- situ to the developing matrix during the preparation of the matrix. The excitation and emission spectra of these molecules are examined in liquid phase to evaluate the effect of varying substitution pattern on luminescence characteristics. The photo luminescence characteristics are also measured from a solid thin film to explore the effect of the matrix on emission wavelengths. These materials show potentiality for their applications in thin film electro luminescence devices whose fabrication and properties are finally discussed.
Organic polythiophene polymers are known to be good electrical conductors, however they are lacking of chemical and mechanical stability. In this paper we describe a synthesis of polyethylene dioxythiophene-polystyrene sulfonate (PEDT-PSS) doped sol-gel polyceram material to improve chemical and mechanical properties of PEDT-PSS thin films. Thin films are fabricated by spin and spray coating methods from polymer-sol-gel solutions on sodalime glass, polyurethane, polycarbonate (PC) and polymethyl methacrylate (PMMA) substrates. The effects of different kinds of silicon dioxide network forming sol-gel precursors are investigated in terms of the electrical conductivity and the stability of the electrical conducting properties against various atmospheres and chemicals. Optical transmittances at the visible wavelength region and refractive indices are also determined. Results indicate that a type and an amount of the sol-gel silane precursor have an effect on the electrical, optical and chemical properties of these films. The most conductive and stable coatings are formed when glycidyloxypropyltrimethoxysilane is used as a sol-gel precursor. The maximum conductivity obtained for 150 nm thick film is 17 S/cm. Finally some of the applications, such as antistatic protection coatings on plastics and optical thin film devices of these polycerams are described.
We are developing a silicon-based micro-optical table (MOT) on which various passive and active optical elements can be positioned with sufficient accuracy so that no further alignment is necessary. In order to achieve a zero-alignment assembly of micro-optical systems, we take advantage of lithographic patterning. Conventional lithography is used in combination with a deep reactive ion etch (DRIE) process for silicon in order to pattern a silicon substrate that plays the role of a micro-optical table. Lithography is also used to pattern optical and opto-mechanical structures on optical elements. Specifically, the hybrid sol-gel method is employed in the fabrication of optical and opto-mechanical structures into a photosensitive glass materials. High optical quality thick films and structures are fabricated by a one-step spin-coating process followed by direct UV imprinting. We have achieved a material thickness of 27.5 microns and a maximum patterned thickness of 17.4 microns at an aspect ratio of 0.6. The material exhibits a minimum transmittance of 97 percent between 400-1100 nm, an index of refraction of 1.49, and an rms surface of 14.8 roughness of 14.8 nm after development.
We demonstrate the design and performance of an array-type diffractive element, which is capable of modifying the beam of a matrix-type vertical-cavity-surface-emitting-laser (VCSEL). The diffractive element was designed for line-of-sight or non- line-of-sight multi-beam transmitter with a maximum illuminating angle of 50 degrees. To demonstrate wide-angle illumination, a single element providing the largest 50-degree illumination angle was designed and fabricated. The element was designed in the paraxial domain by the geometrical map- transformation method. Beam deflection to the desired angle was performed by Lohmann's detour-phase principle. The local diffraction efficiency of the binary element was analyzed by rigorous electromagnetic diffraction theory. The element was fabricated as a pixel-array, in which the pixel size was 200 nm X 200 nm and the size of the element was 250 micrometer X 250 micrometer. The performance of the element was characterized by measuring the irradiance at the observation plane by a CCD-camera, and by measuring the diffraction efficiencies of three diffraction orders with a separate detector. The measured diffraction efficiency and the irradiance distribution of the element for the -1st order was 27.5%, which was in fair agreement with the calculated 23.9% efficiency after taking the real properties of the VCSEL beam into consideration.
In this paper we present the results of the first fabrication and micro-assembly experiments of a silicon- wafer based micro-optical table (MOT). Based on these experiments, estimates of position accuracy are reported. We also report on progress in fabrication of lens elements in a hybrid sol-gel material (HSGM). Diffractive optical elements have been patterned in a 13-micron thick HSGM layer on a 150-micron thick soda-lime glass substrate. The measured rms surface roughness was 20 nm. Finally, we describe modeling of MOT systems using non-sequential ray tracing.
A new strip-loaded structure for ion-exchanged waveguide amplifiers in Er3+-doped glass is suggested. The fabrication of these waveguides lacks steps such as mask deposition and burial process that can be critical for some glasses. A simple numerical modeling shows that similar, or even higher, gain values as in ion-exchanged buried waveguides can be achieved. Preliminary experimental data for the fabrication of the strip-loaded structure are also reported.
Sol-gel materials have been widely used for the fabrication of micro-optical devices during the last decade. Motivation for the sol-gel processing has been the low cost and a large variety of fabrication techniques and material properties. One of the interesting possibilities has been to use sol-gel glasses as an erbium host for integrated optics amplifiers. Several research results have been published, but sol-gel processing has not yet proven its potential for efficient devices in this important and rapidly advancing field. There are still some problems to be solved, such as the removal of residual water from sol-gel matrices and the process reliability and reproducibility. In this paper, we review the present status of the sol-gel materials and discuss their potential and challenges for the erbium-doped waveguide amplifiers.
Organically modified photosensitive hybrid glasses are synthesized and used for the fabrication of diffractive optical elements. The material synthesis is based on a sol-gel process. The materials are spin-deposited onto glass substrate that also have a significant role in the component assembly. The synthesized material has a negative tone property under UV-radiation and they can be patterned by a conventional UV- lithography process. Binary diffractive lenses are photoimprinted through an amplitude contact mask. Optical properties and surface roughness of the materials and elements are evaluated. Diffraction efficiencies of the elements are also measured. The process and material optimization for the reliable fabrication of integrated optics devices is carried out.
Antimony doped tin dioxide (SnO2:Sb) thin films are fabricated by a new simplified sol-gel process. Films are prepared from an alcoholic solution of SnCl4(DOT)4H2O doped with SbCl3. Films are deposited by the spin coating process on sodalime glass, borosilicate glass, silicon wafers and ceramic alumina substrates. The chemical reactions during the heat treatment are monitored by DSC and TG. The chemical composition of the coatings are determined by scanning electron microscopy (SEM). Sheet resistance, Rs, is measured using a linear four-probe technique. Optical properties of the films are also determined. The resistivity of the thin films are presented as a function of the antimony doping level. The smallest sheet resistance of 200 (Omega) /$DAL is found for a 250 nm thick coating on a borosilicate substrate. It is observed that the sheet resistance does not decrease linearly with increasing film thickness. Fabrication possibilities of these materials for the integrated optics based sensors including patterning methods are discussed.
We present two techniques to use hybrid sol-gel materials for electron-beam lithography and direct writing of surface relief diffractive elements. We are able to obtain direct physical electron beam etching of hybrid sol-gel glass and variable- doses can induce complex multi-phase-level diffractive elements and apodized sol-gel waveguide gratings. We are also able to obtain hybrid so-gel glass formation under the electron radiation, so that material can be used as a negative resist in electron-beam lithography. Both of these techniques are promising for the fabrication of submicron optical components and micromachining tools such as embossing masters for the replication.
Particle boards are very common products in the wood industry. However, increasing use of this product with its derivatives, imposes new challenges in terms of inspection techniques. Lockin thermography is an attractive tool for such a task. In this paper, fundamentals of lockin thermography are presented followed by several representative examples of particle board inspection.
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