There is demand for optics for EUV applications including microscopy and diagnostic devices for EUV lithography exposure masks. Au and W are common materials for such applications, but they have relatively low theoretical diffraction efficiency. Ru is a good candidate for 13.5 nm wavelength applications as it has greater theoretical efficiency than Au or W. It also has the benefit of oxidizing less during plasma etching or on exposure to air. Oxidation can be a concern for materials with higher theoretical zone plate efficiency such as molybdenum because it can lead to a significant decrease in theoretical efficiency. Additionally, molybdenum also presents more etching challenges than Ru, particularly concerning sidewall verticality. Our work involves the fabrication and characterization of diffraction gratings and zone plates for 13.5 nm EUV applications. The fabrication of W and Ru phase zone plates with 80 nm outer zone width through electron beam lithography and plasma etching is presented. Characterization of the zone plate through SEM and STEM imaging, as well as EDX analysis, was performed. A comparison between the W and Ru zone plates is given.
We describe a prototyping process for silicon nitride photonic integrated circuits, targeting applications in the visible and near-infrared wavelength ranges. The platform is based on direct-write electron beam lithography technology and provides a route toward the rapid fabrication of passive and thermo-optic active photonic devices. The fabrication turnaround time is on the order of several weeks, and critical feature sizes are demonstrated down to 100 nm which enables the fabrication of subwavelength metastructures. Two waveguiding material thicknesses have been demonstrated, 150 nm for visible light applications and 400 nm for infrared.
Diffractive optics for nanoscale X-ray imaging, particularly for high energy X-rays, require nanoscale width features with high-aspect ratio thick metal rings (zones) for efficient focusing of X-rays. Electron beam lithography (EBL) has many benefits for producing such structures, allowing patterning of high-resolution and accurately placed structures with placement precisions within a few nanometers over several hundred micrometers. Despite the benefits of EBL, efforts to achieving very high (> 20) aspect ratio structures requires non-standard techniques to overcome issues such as collapse or distortion of the zones and maintaining vertical sidewalls. Methods to increase the effective height of the zones, such as multi-layered lithography and stacking of zone plates present several challenges, such as cost, low yield, and difficult alignment. In this work, we present a new fabrication method, using a single-step-exposure, to pattern both sides of a thin 100 nm membrane to increase the overall effective thickness of a zone plate. By overcoming some of the effects of beam broadening during the electron beam exposure, this process is able maintain provide high-resolution lithography, despite the interfacial membrane layer separating the two resist films. This technique has several advantages, including perfect alignment of the two layers, reduced lithography and fabrication steps, increased mechanical strength and lifetime, producing high-efficiency and resolution zone plates. In this work, double-layer zone plates have been fabricated with outer zone widths down to 25 nm. Results will be presented comparing double-layered zone plates with single-layer zone plates for efficiency and resolution.
Jan Geilhufe, Adam F. Leontowich, Russ Berg, Chris Regier, Darwin Taylor, Jian Wang, John Swirsky, Chithra Karunakaran, Robert Peters, Mirwais Aktary, Adam Hitchcock, Stephen Urquhart
A new scanning transmission X-ray microscope (STXM) optimized for cryo-spectro-tomography with soft X-rays has been designed, built and commissioned at Canadian Light Source (CLS) beamline 10ID1 (130-2700 eV). It is controlled via a new python-based software package, pySTXM. A liquid N2 goniometer (Gatan 630, -80° to 80°), mounted on a computer controlled (x,y,Theta) tilt stage allows for spectro-tomographic measurements at cryogenic temperatures (-180°C) which reduces radiation damage. The CLS cryo-STXM is unique among the set of soft X-ray STXMs currently installed around the world. Details of the cryo-STXM design and examples of its performance will be presented.
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