Multilayer Laue lenses (MLLs) are promising optics for high efficiency nano focusing in the hard x-ray regime. However, since MLLs are one-dimensional focusing elements, a pair of MLLs need to be orthogonally aligned with respect to each other to achieve point focusing. This involves eight independent motions with nanoscale resolutions. This requirement poses significant technical challenges for a microscopy system and requires a highly specialized and stable instrument. The development of monolithic 2D MLL nano focusing optics could greatly reduce the instrument complexity, increase focusing stability, and minimize the degrees of a nanoscale motion needed for operating the MLL optics. A critical step in building 2D MLL optics is to ensure the orthogonality between two MLLs during the alignment. In this work, we report our approach for precise angular alignment of 2D MLL optics. This process, by utilizing a machine learning algorithm on the interferometer data, can automatically and precisely detect the small orthogonality error of 2D MLL optics. It is easy to use, accurate, and robust, and remarkably simplifies the procedure of 2D MLL alignment.
High-NA EUV lithography required for continued extreme downscaling of Si devices demands ultrathin photoresists with high EUV patterning performance and etch resistance. This talk briefs our current efforts on synthesizing new organic-inorganic hybrid resists based on atomic layer deposition (ALD) techniques and characterizing their electron beam and EUV patterning characteristics. Two distinctive approaches are discussed–vapor-phase infiltration (VPI) and molecular ALD (MALD), where the former utilizes an infiltration of gaseous inorganic precursors into existing organic resists and the latter a cyclic layering of organic and inorganic moieties. Featured systems include an indium-oxide-infiltrated PMMA and a MALD hybrid resist comprising trimethylaluminum (TMA) and hydroquinone (HQ). Given the facile implementablility and control of resist composition and characteristics, the ALD-based hybrid resist synthesis has a potential for enabling high-performance EUV photoresist systems.
Infiltration synthesis of vapor-phase precursors is ex-situ route of converting established polymeric resists into hybrids. The concept initially modelled over polymethylmethacrylate (PMMA)-AlOx hybrid has been expanded to infiltrating several metal oxide moieties into high sensitivity resist (HSR). Beyond implementing single metal oxide species, alloyed infiltration is explored as a means to limit pattern roughness originating from granular crystallites. Lithography performance of these new generation of hybrid positive tone resists is assessed towards contact-hole patterning.
High-NA EUV lithography–scheduled to be implemented in a few years for high-volume manufacturing of extremely downscaled Si devices with 2 nm node and beyond–demands ultrathin organic-inorganic hybrid photoresists with high EUV sensitivity and etch resistance. In this work, we synthesized a positive-tone hybrid photoresist composed of PMMA infiltrated with molecular network of indium oxide by vapor-phase infiltration (VPI), an ex-situ inorganic hybridization method derived from atomic layer deposition, and evaluated its patterning characteristics by electron-beam and EUV lithography (EBL and EUVL). The hybrid resist featured significantly enhanced etch resistance under dry etching but also the critical doses of 300 uC/cm2 for EBL and 60 mJ/cm2 for EUVL, both largely comparable to those of PMMA. Unlike alumina infiltration in PMMA that has been demonstrated previously, it was found that the weak binding nature of trimethyl indium (TMIn), the gaseous precursor used to infiltrate indium oxide in PMMA matrix, to the carbonyl group in PMMA enabled a uniform distribution of the oxide content across the PMMA thickness. However, it also led to undesired residue in the developed regions due to the strong interaction between the Lewis-basic hydroxyl groups on the surface of starting Si substrate with infiltrated TMIn. The residue issue could be mitigated by passivating the Si surface by hexamethyldisilizane (HMDS) and combining the acid/base rinse and oxygen plasma descum. The results not only hint at the potential of VPI-based ex-situ hybridization in developing novel hybrid EUV photoresists but also highlight the technological details that must be addressed to enable high EUVL performance in the infiltrated hybrid resist system.
Infiltration synthesis is an emerging material hybridization technique. Starting with a brief dive into infiltration synthesis mechanism, I will present our pioneering work on ex-situ conversion of conventional organic photoresists into hybrid EUV resists as well as the generation of mechanically resilient hybrids with one of the highest storage elastic strain energy capacities for potential applications in MEMS technologies. I will also overview the use of infiltration synthesis approach for hybridizing nanopatterned polymer templates and self-assembled block copolymer thin films to form robust dry etch masks for pattern transfer as well as direct-writing oxide nanostructures for optoelectronic device applications.
We have developed an organic-inorganic hybrid resist platform featuring versatile ex-situ control of its performance by incorporating inorganic elements using vapor-phase infiltration (VPI) into standard organic resists. With poly(methyl methacrylate) (PMMA)-AlOx hybrid as a model composition we unveiled controllability of the critical exposure dose, contrast (as high as ~30), and etch resistance; estimated Si etch selectivity over ~300, demonstrating high aspect ratio ~17 with ~30 nm resolution Si fin-structures. Building upon the demonstration of PMMA-AlOx hybrid resist, we expanded our material portfolio to a high sensitivity resist and other inorganic moieties. We present preliminary results obtained from the extreme ultraviolet (EUV) lithography dose tests conducted on corresponding infiltrated hybrids and optimization of infiltration with the help of transmission electron microscopy (TEM).
We demonstrate a simple ex-situ inorganic infiltration route for transforming standard organic resists into high-performance positive tone hybrid resist platform. A model thin film PMMA-AlOx hybrid resist system has been synthesized by hybridization of PMMA with AlOx and investigated for electron beam lithography. The approach possesses full controllability of the resist performance in terms of critical does, patterning contrast reaching up to 30 and etch resistance for plasma-based pattern transfer processes. The high selectivity Si etching capability demonstrated using a low-temperature cryo-Si etch process, based on the controlled infiltration outperforms commercial resists and typical hard mask material thermal SiO2, with estimated achievable selectivity in excess of ~300. Si nanostructures down to ~30 nm with aspect ratio up to ~17 are also transferred into the Si substrate. Easy implementation and adaptability for different inorganic infiltrations, this platform is well capable of potentially delivering the resist performance and throughput necessary for EUV lithography.
Hard X-ray microscopy is a powerful scientific tool capable of providing sub-10 nm spatial resolution imaging of material’s chemical composition and internal structure. Multilayer Laue Lenses (MLLs) have been developed and used for hard x-ray nanofocusing. MLLs are one dimensional X-ray diffractive optics fabricated through multilayer deposition and sectioning. An orthogonal alignment of two MLLs yields a point focus; 10 milli-degree orthogonality and sub-10 µm positioning accuracy along the beam direction is required to avoid astigmatism and achieve 10 nm focal spot size at 12 keV photon energy. Up-to-date, developed x-ray microscopy systems were equipped with eight degrees of nano-scale motion to perform full alignment of individual MLL optics. Bonding of two individual lenses together in pre-determined configuration significantly simplifies alignment process and makes them compatible with a more conventional Zone Plate – based microscopes. In this work, we give an overview of the existing bonding effort and present our approach to fabricate a monolithic 2D MLL optic.
The external cavity tunable mid-infrared emitters based on Littrow configuration and utilizing three stages type-I quantum well cascade diode laser gain elements were designed and fabricated. The free-standing coated 7.5-μm-wide ridge waveguide lasers generated more than 30 mW of continuous wave power near 3.25 μm at 20°C when mounted epi-side-up on copper blocks. The external cavity lasers (ECLs) utilized 2-mm-long gain chips with straight ridge design and anti-/neutral-reflection coated facets. The ECLs demonstrated narrow spectrum tunable operation with several milliwatts of output power in spectral region from 3.05 to 3.25 μm corresponding to ∼25 meV of tuning range.
KEYWORDS: Photon counting, Sensors, Monte Carlo methods, Selenium, Crystals, Semiconductors, X-ray imaging, Detector development, X-rays, Signal detection, Breast imaging, Electrodes, Signal attenuation, Prototyping, Luminescence
Photon counting detectors (PCD) with energy discrimination capabilities have the potential for improved detector performance over conventional energy integrating detectors. Additionally, PCDs are capable of advanced imaging techniques such as material decomposition with a single exposure, which may have significant impact in breast imaging applications. Our goal is to develop a large area amorphous Selenium (a-Se) photon counting detector. By using our novel direct conversion field-Shaping multi-Well Avalanche Detector (SWAD) structure, the inherent limitations of low charge conversion gain and low carrier mobility of a-Se can be overcome. In this work we developed a spatio-temporal charge transport model to investigate the effects of charge sharing, energy loss and pulse pileup for SWAD. Using a monoenergetic 20 keV source we found that 32% of primary interactions have K-fluorescence emissions that escape the target pixel, 62.5% of which are reabsorbed in neighboring pixels, while 37.5% escape the detector entirely for a 100 μm × 100 μm pixel size. Simulated pulse height spectra for an input count rate of 50,000 counts/s/pixel with a 2 μs dead time was also generated, showing a photopeak FWHM = 2.6 keV with ~10% pulse pileup. Additionally we present the first time-of-flight (TOF) measurements from prototype SWAD samples, showing successful unipolar time differential (UTD) charge sensing. Our simulation and initial experimental results show that SWAD has potential towards making a large area a-Se based PCD for breast imaging applications.
Self-organizing block copolymer thin films hold promise as a photolithography enhancement material for the 22-nm microelectronics technology generation and beyond, primarily because of their ability to form highly uniform patterns at the relevant nm scale dimensions. Importantly, the materials are chemically similar to photoresist and can be implemented in synergy with photolithography. Beyond the challenges of achieving sufficient control of self-assembled pattern defects and feature roughness, block copolymer-based patterning requires creation of robust processes for transferring the polymer patterns into underlying electronic materials. Here, we describe research efforts in hardening block copolymer resist patterns using inorganic materials and high aspect ratio plasma etch transfer of self-assembled patterns to silicon using fluorine-based etch chemistries.
Self-organizing block copolymer thin films hold promise as a photolithography enhancement material for the 22-nm
microelectronics technology generation and beyond, primarily because of their ability to form highly uniform patterns at
the relevant nanometer-scale dimensions. Importantly, the materials are chemically similar to photoresists and can be
implemented in synergy with photolithography. Beyond the challenges of achieving sufficient control of self-assembled
pattern defectivity and feature roughness, block copolymer-based patterning requires creation of robust processes for
transferring the polymer patterns into underlying electronic materials. Here, we describe research efforts in hardening
block copolymer resist patterns using inorganic materials and high aspect ratio plasma etch transfer of self-assembled
patterns to silicon using fluorine-based etch chemistries.
KEYWORDS: Zone plates, Gold, Electron beam lithography, Plating, Hard x-rays, X-rays, Photoresist processing, Reactive ion etching, Electroplating, Etching
Fresnel zone plates are important x-ray diffractive optics which offer a focusing resolution approaching the theoretical limit. In hard x-ray region, the refractive indices of all the materials are close to unity, which requests thick zone plate to achieve a reasonable efficiency. It makes high-resolution zone plate extremely difficult to fabricate due to its high aspect ratio. We report a LIGA-like fabrication process employing e-beam resist HSQ as the plating mold material, which is relative simply compared with traditional processes. 1-μm-thick gold zone plates with 80-nm-wide outermost zone have been fabricated with this process.
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