Improving the Resolution and Throughput of Achromatic Talbot Lithography

High-resolution patterning of periodic structures over large areas has several applications in science and technology. One such method, based on the long-known Talbot effect observed with diffraction gratings, is achromatic Talbot lithography (ATL). This method offers many advantages over other techniques, such as high resolution, large depth of focus, high throughput, etc. Although the technique has been studied in the past, its limits have not yet been explored. Increasing the efficiency and the resolution of the method is essential and might enable many applications in science and technology. In this work, we combine this technique with spatially coherent and quasi-monochromatic light at extreme ultraviolet (EUV) wavelengths and explore new mask design schemes in order to enhance its throughput and resolution. We report on simulations of various mask designs in order to explore their efficiency. Advanced and optimized nanofabrication techniques have to be utilized to achieve high quality and efficient masks for ATL. Exposures using coherent EUV radiation from the Swiss light source (SLS) have been performed, pushing the resolution limits of the technique for dense hole or dot patterning down to 40 nm pitch. In addition, through extensive simulations, alternative mask designs with rings instead of holes are explored for the efficient patterning of hole/dot arrays. We show that these rings exhibit similar aerial images to hole arrays, while enabling higher efficiency and thereby increased throughput for ATL exposures. The mask designs with rings show that they are less prone to problems associated with pattern collapse during the nanofabrication process and therefore are promising for achieving higher resolution

Magnetic metamaterials in the blue range using aluminum nanostructures

We report an experimental and theoretical study of the optical properties of two-dimensional arrays of aluminum nanoparticle in-tandem pairs. Plasmon resonances and effective optical constants of these structures are investigated and strong magnetic response as well as negative permeability are observed down to 400 nm wavelength. Theoretical calculations based on the finite-difference time-domain method are performed for various particle dimensions and lattice parameters, and are found to be in good agreement with the experimental results. The results show that metamaterials operating across the whole visible wavelength range are feasible.Comment: 3 pages, 4 figure

Changes in the near edge X-ray absorption fine structure of hybrid organic-inorganic resists upon exposure

We report on the near edge X-ray absorption fine structure (NEXAFS) spectroscopy of hybrid organic-inorganic resists. These materials are nonchemically amplified systems based on Si, Zr, and Ti oxides, synthesized from organically modified precursors and transition metal alkoxides by a sol-gel route and designed for ultraviolet, extreme ultraviolet and electron beam lithography. The experiments were conducted using a scanning transmission X-ray microscope (STXM) which combines high spatial-resolution microscopy and NEXAFS spectroscopy. The absorption spectra were collected in the proximity of the carbon edge (~ 290 eV) before and after in situ exposure, enabling the measurement of a significant photo-induced degradation of the organic group (phenyl or methyl methacrylate, respectively), the degree of which depends on the configuration of the ligand. Photo-induced degradation was more efficient in the resist synthesized with pendant phenyl substituents than it was in the case of systems based on bridging phenyl groups. The degradation of the methyl methacrylate group was relatively efficient, with about half of the initial ligands dissociated upon exposure. Our data reveal that the such dissociation can produce different outcomes, depending on the structural configuration. While all the organic groups were expected to detach and desorb from the resist in their entirety, a sizeable amount of them remain and form undesired byproducts such as alkene chains. In the framework of the materials synthesis and engineering through specific building blocks, these results provide a deeper insight into the photochemistry of resists, in particular for extreme ultraviolet lithography

Lithographic performance of ZEP520A and mr-PosEBR resists exposed by electron beam and extreme ultraviolet lithography

Pattern transfer by deep anisotropic etch is a well-established technique for fabrication of nanoscale devices and structures. For this technique to be effective, the resist material plays a key role and must have high resolution, reasonable sensitivity and high etch selectivity against the conventional silicon substrate or underlayer film. In this work, the lithographic performance of two high etch resistance materials was evaluated: ZEP520A (Nippon Zeon Co.) and mr-PosEBR (micro resist technology GmbH). Both materials are positive tone, polymer-based and non-chemically amplified resists. Two exposure techniques were used: electron beam lithography (EBL) and extreme ultraviolet (EUV) lithography. These resists were originally designed for EBL patterning, where high quality patterning at sub-100 nm resolution was previously demonstrated. In the scope of this work, we also aim to validate their extendibility to EUV for high resolution and large area patterning. To this purpose, the same EBL process conditions were employed at EUV. The figures of merit, i.e. dose to clear, dose to size, and resolution, were extracted and these results are discussed systematically. It was found that both materials are very fast at EUV (dose to clear lower than 12 mJ/cm2) and are capable of resolving dense lines/space arrays with a resolution of 25 nm half-pitch. The quality of patterns was also very good and the sidewall roughness was below 6 nm. Interestingly, the general-purpose process used for EBL can be extended straightforwardly to EUV lithography with comparable high quality and yield. Our findings open new possibilities for lithographers who wish to devise novel fabrication schemes exploiting EUV for fabrication of nanostructures by deep etch pattern transfer.Comment: 20 pages, 4 figures, 3 table

Engineering Metal Adhesion Layers That Do Not Deteriorate Plasmon Resonances

Adhesion layers, required to stabilize metallic nanostngtures, dramatically deteriorate the performances of plasmonic sensors, by severely damping the plasmon modes. In this article, we show that these detrimental effects critically depend on the overlap of the electromagnetic near-field of the resonant plasmon mode with the adhesion layer and can be minimized by careful engineering of the latter. We study the dependence of the geometrical parameters such as layer thickness and shape on the near-field of localized plasmon resonances for traditional adhesion layers such as Cr, Ti, and h02. Our experiments and simulations reveal a strong dependence of the damping on the layer thickness, in agreement with the exponential decay of the piasmon near-field. We developed a method to minimize the damping by selective deposition of thin adhesion layers (<1 nm) In a manner that prevents the layer to overlap with the hotspots of the plasmonlc structure. Such a designed structure enables the use of standard Cr and Ti adhesion materials to fabricate robust plasmonic sensors without deteriorating their sensitivity

Squamotous-type sarcomatoid carcinoma of the lung with rhabdomyosarcomatous components

Lung carcinosarcoma is an infrequently biphasic tumor composed of carcinomatous and sarcomatous components. It is divided into endobronchial (squamous-type) and peripheral (glandular type) categories. The carcinomatous component is usually a squamous carcinoma, and the sarcomatous component usually resembles a fibrosarcoma or a malignant fibrous histiocytoma. The presence of rhabdomyoblastic differentiation in such neoplasms is exceedingly rare. There are strong associations with smoking and asbestosis. In this study, we describe a unique case of a 43-year-old man with a 75 packet/year smoking history in whom a rare mixed malignant tumor of the lung was diagnosed and treated by left pneumonectomy. Histological examination of the resected specimen showed squamous cell carcinoma and rhabdomyosarcoma components. Although rare, the association of a sarcomatoid carcinoma of the lung with squamous cell carcinoma and rhabdomyosarcomatous component is possible and should be kept in mind when dealing with these unusual tumors

Evaluation of lab-scale EUV microscopy using a table-top laser source

High brightness Extreme Ultraviolet (EUV) sources for laboratory operation are needed in nano-fabrication and actinic (&quot;at-wavelength&quot;) inspection of the masks for high volume manufacturing in next generation lithography. Laser-plasma EUV sources have the required compactness and power scalability to achieve the demanding requirements. However, the incoherent emission lacks the brightness for single-shot high contrast imaging. On the other hand, fully coherent sources are considered to be unsuitable for full-field sample illumination and prone to speckles. We evaluate the capabilities of a lab-scale amplified-spontaneousemission (ASE) EUV laser source to combine brightness and high quality imaging with full-field imaging, along with rapid acquisition and compactness

Nanolithographic Top‐Down Patterning of Polyoxovanadate‐based Nanostructures with Switchable Electrical Resistivity

The top-down fabrication of ∼10 nm vanadium oxide nanostructures by electron beam lithography based on a molecular vanadium oxide resist material is reported. The new material enables the large-scale deposition of electrically switchable nanostructures which can be directly incorporated in established e-beam lithography. The findings could in future enable the top-down fabrication of functional metal oxide nanostructures in the < 10 nm domain. The top-down lithographic fabrication of functional metal oxide nanostructures enables technologically important applications such as catalysis and electronics. Here, we report the use of molecular vanadium oxides, polyoxovanadates, as molecular precursors for electron beam lithography to obtain functional vanadium oxide nanostructures. The new resist class described gives access to nanostructures with minimum dimensions close to 10 nm. The lithographically prepared structures exhibit temperature-dependent switching behaviour of their electrical resistivity. The work could lay the foundation for accessing functional vanadium oxide nanostructures in the sub-10-nm domain using industrially established nanolithographic methods