M. Hojeij

Nonlinear superchiral meta-surfaces: Tuning chirality and disentangling non-reciprocity at the nanoscale

Circularly polarized light is incident on a nanostructured chiral meta-surface. In the nanostructured unit cells whose chirality matches that of light, superchiral light is forming and strong optical second harmonic generation can be observed.

Evaluation of EUV resist performance with interference lithography towards 11 nm half-pitch and beyond

The performance of EUV resists is one of the main challenges for the cost-effectiveness and the introduction of EUV lithography into high-volume manufacturing. The EUV interference lithography (EUV-IL) is a simple and powerful technique to print periodic nanostructures with a resolution beyond the capabilities of other tools. In addition, the well-defined and pitch-independent aerial image of the EUV-IL provides further advantages for the analysis of resist performance. In this paper, we present evaluation of chemically-amplified resists (CAR) and inorganic resists using EUV-IL. We illustrate the performance of the tool through a reproducibility study of a baseline resist over the course of 16 months. A comparative study of the performance of different resists is presented with the aim of resolving patterns with CARs for 16 nm half-pitch (HP) and 11 nm HP. Critical dimension (CD) and line-edge roughness (LER) are evaluated as functions of dose for different process conditions. With a CAR with about 10 mJ/cm2 sensitivity, 18 nm L/S patterns are obtained with low LER and well-resolved patterns are achieved down to 16 nm HP. With another CAR of about 35 mJ/cm2 sensitivity, L/S patterns with low LER are demonstrated down to 14 nm HP. Resolved patterns are achieved down to 12 HP, demonstrating the capability of its potential towards 11 nm HP if pattern collapse mitigation can be successfully applied. With EUV-sensitive inorganic resists, patterning down to 8 nm has been realized. In summary, we show that resist platforms with reasonable sensitivities are already available for patterning at 16 nm HP, 11 nm HP, and beyond, although there is still significant progress is needed. We also show that with decreasing HP, pattern collapse becomes a crucial issue limiting the resolution and LER. Therefore resist stability, collapse mitigation, and etch resistance are some of the significant problems to be addressed in the development of resist platforms for future technology nodes.

Generation of high-resolution kagome lattice structures using extreme ultraviolet interference lithography

High-resolution kagome lattice structures with feature sizes down to the sub-50u2009nm regime are fabricated using diffraction-based extreme ultraviolet interference lithography. The resulting interference pattern of multiple beams is sensitive to the relative phase of the interfering beams. The precise control of their phases is achieved by precise positioning of transmission diffraction gratings on a mask using a high-end electron beam lithography tool. The presented method may find applications in providing high-resolution and large-area kagome lattice structures for studies on frustrated magnetic systems, photonic crystals, and plasmonics.

Evaluation of resist performance with EUV interference lithography for sub-22-nm patterning

The performance of EUV resists is a key factor for the cost-effective introduction of EUV lithography. Although most of the global effort concentrates on resist performance at 22 nm half-pitch, it is crucial for the future of EUVL to show its extendibility towards further technology nodes. In the last years, the EUV interference lithography tool at Paul Scherrer Institute, with its high-resolution and well-defined areal image, has been successfully employed for resist performance testing. In this paper, we present performance (dose, CD, LER) of a chemically-amplified resist for a range of 16 nm to 30 nm HP. Cross-sectional SEM images of the patterns are presented providing valuable insight into the resists performance and failure mode. The reproducibility of our experiments are presented by repeating the same exposures with constant process conditions over the course of several months, demonstrating the excellent stability of the tool as well as the long shelf-life of our baseline resist. In addition, a comparative study of performance (dose, CD, LER) of different inorganic resists is provided. Patterns of 16 nm and 10 nm HPs are demonstrated with an EUV CAR and inorganic resists, respectively. Moreover, initial results of patterning with 6.5 nm wavelength are presented.

High-resolution nanopatterning by achromatic spatial frequency multiplication with electroplated grating structures

The authors demonstrate generation of high-resolution nanostructures using achromatic spatial frequency multiplication in the extreme ultraviolet wavelength region. The technique based on the achromatic Talbot effect is used for periodic transmission gratings under wideband illumination, enabling one- and two-dimensional nanopatterns with sub-20 nm feature sizes. The transmission masks with desired properties are fabricated with electron-beam lithography followed by electroplating of gold. Features sizes down to 12 nm are obtained. The presented technique provides high-throughput and large-area nanopatterning with great flexibility in tuning pattern parameters such as linewidth and dot size.

Distributing the Optical Near‐Field for Efficient Field‐Enhancements in Nanostructures

We are grateful to Saloomeh Shariati from the crypto group in the Universite Catholique de Louvain, for helpful discussion on the measures of the uniformity in images. We acknowledge financial support from the fund for scientific research Flanders (FWO-V), the K. U. Leuven (CREA, GOA), Methusalem Funding by the Flemish government and the Belgian Inter-University Attraction Poles IAP Programmes. V. K. V. and S. V. are grateful for the support from the FWO-Vlaanderen. B. DC. is thankful to the IWT.

Rendering dark modes bright by using asymmetric split ring resonators

We have studied both theoretically and experimentally symmetric and asymmetric planar metallic Split Ring Resonators. We demonstrate that introducing structural asymmetry makes it possible to excite several higher order modes of both even (l = 2) and odd (l = 3, 5) order, which are otherwise inaccessible for a normally incident plane wave in symmetric structures. Experimentally we observe that the even mode resonances of asymmetric resonators have a quality factor 5.8 times higher than the higher order odd resonances.