Despite the fact that the resolution of conventional contact/proximity lithography can reach feature sizes down to ~0.5- 0.6 micrometers, the accurate control of the linewidth and uniformity becomes already very challenging for gratings with periods in the range of 1-2 μm. This is particularly relevant for the exposure of large areas and wafers thinner than 300 μm. If the wafer or mask surface is not fully flat due to any kind of defects, such as bowing/warpage or remaining topography of the surface in case of overlay exposures, noticeable linewidth variations or complete failure of lithography step will occur. We utilized the newly developed Displacement Talbot lithography to pattern gratings with equal lines and spaces and periods in the range of 1.0 to 2.4 μm. The exposures in this lithography process do not require contact between the mask and the wafer, which makes it essentially insensitive to surface planarity and enables exposures with very high linewidth uniformity on thin and even slightly deformed wafers. We demonstrated pattern transfer of such exposures into Si substrates by reactive ion etching using the Bosch process. An etching depth of 30 μm or more for the whole range of periods was achieved, which corresponds to very high aspect ratios up to 60:1. The application of the fabricated gratings in phase contrast x-ray imaging is presented.
We present the results of patterning chemically-amplified and inorganic resists at 6.5 nm wavelength using interference lithography. Well-resolved patterns down to 22 nm HP are obtained. Dose-dependent line-edge roughness and critical dimensions in the resolution range of 50-22 nm half-pitch are obtained using 13.5 and 6.5 nm wavelength. The performances of the resists are compared for both cases. Increased line-edge roughness is observed for patterning 6.5 nm compared to the patterning at 13.5 nm wavelength.
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/cm<sup>2</sup> 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/cm<sup>2</sup> 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.
In this work, we show that closely-spaced gold nanohoops periodically distributed in a square lattice can provide
a strong magnetic response in the near infrared regime when illuminated under normal incidence (perpendicular
to the structure plane). Therefore, just a single metallic layer is needed to achieve the magnetic activity. A key
point to achieve this response is that the aspect ratio must be higher than 1. Transmission and reflection spectra
taken by means of a Fourier-Transform Infrared spectrometer show a strong absorbance peak at a wavelength that
can be tuned by modifying the hole radius of the nanohoops or the underlying dielectric substrate. Numerical
simulations show that at the resonance wavelength a virtual current loop is created, giving rise to a strong
magnetic moment and a large magnetic field enhancement in the space between nanohoops.
Metallic wire-grid polarizers (WGP) transmit TM-polarized light (transverse magnetic) and reflect TE polarization
(transverse electric) efficiently. They are compact, planar and compatible with integrated circuit (IC) fabrication, which
simplifies their use as optical components in nanophotonic, fiber optic, display, and detector devices. In this work, Al bi-layer
WGPs were designed and numerically simulated using finite element methods. Optical properties of the polarizers
were analyzed in the deep-ultraviolet (DUV) to infrared (IR) regions. It was observed that Al bi-layer WGPs show
broadband and high TM transmission and extinction ratio. A comparison of the performances of single and bi-layer
WGPs show that the latter is highly advantageous over the former one. An extensive study of the dependence of the
optical properties of single and bi-layer WGPs on structural parameters, such as period, metal thickness, and, duty cycle
(DC), is provided. Optimal structural parameters are obtained within the feasible parameters in terms of nanofabrication.
An Al bi-layer polarizer with a period of 80 nm and a metal layer thickness of 40 nm showed transmission up to 80%
and extinction of 40 dB (10<sup>4</sup>) and broadband polarizing behavior down to a wavelength of 250 nm.
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 resist's
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.