2 research outputs found
Novel EUV mask absorber evaluation in support of next-generation EUV imaging
In next-generation EUV imaging for foundry N5 dimensions and beyond, inherent pitch- and orientation-dependent effects on wafer level will consume a significant part of the lithography budget using the current Ta-based mask. Mask absorber optimization can mitigate these so-called mask 3D effects. Thin metal absorbers like Ni and Co have been experimentally investigated due to their high EUV absorption, but they pose challenges on the current technology of subtractive mask patterning [1]. A simulation study of attenuated EUV phase shift masks has identified through multi objective optimization superior imaging solutions for specific use cases and illumination conditions [2]. Evaluating novel EUV mask absorbers evolves on two levels, demonstrating (1) improvements from lithographic perspective and (2) compatibility with the full mask supply chain including material deposition, absorber patterning, scanner environment compatibility and mask lifetime. On the lithographic level, we have identified regions based on the material optical properties and their gain in imaging performance compared to the reference Ta-based absorber. Within each improvement region we engineered mask absorber materials to achieve both the required imaging capabilities, as well as the technical requirements for an EUV mask absorber. We discuss the material development of Te-based alloys and Ag-based layered structures, because of their high EUV extinction. For the attenuated phase shift materials, we start from a Ru-base material, due to its low refractive index, and construct Ru-alloys. On the experimental level, we examined our novel mask absorber materials against an initial mask absorber requirement list using an experimental test flow. Candidate materials are evaluated on film morphology and stability through thermal, hydrogen, EUV loading, and chemical cleaning, for their EUV optical constants by EUV reflectometry, as well as preliminary for selective dry etch. The careful mask absorber evaluation, combining imaging simulations and experimental material tests, allowed us to narrow down to promising combinations for novel EUV mask absorbers
InAs-Al Hybrid Devices Passing the Topological Gap Protocol
We present measurements and simulations of semiconductor-superconductor
heterostructure devices that are consistent with the observation of topological
superconductivity and Majorana zero modes. The devices are fabricated from
high-mobility two-dimensional electron gases in which quasi-one-dimensional
wires are defined by electrostatic gates. These devices enable measurements of
local and non-local transport properties and have been optimized via extensive
simulations for robustness against non-uniformity and disorder. Our main result
is that several devices, fabricated according to the design's engineering
specifications, have passed the topological gap protocol defined in Pikulin
{\it et al.}\ [arXiv:2103.12217]. This protocol is a stringent test composed of
a sequence of three-terminal local and non-local transport measurements
performed while varying the magnetic field, semiconductor electron density, and
junction transparencies. Passing the protocol indicates a high probability of
detection of a topological phase hosting Majorana zero modes. Our experimental
results are consistent with a quantum phase transition into a topological
superconducting phase that extends over several hundred millitesla in magnetic
field and several millivolts in gate voltage, corresponding to approximately
one hundred micro-electron-volts in Zeeman energy and chemical potential in the
semiconducting wire. These regions feature a closing and re-opening of the bulk
gap, with simultaneous zero-bias conductance peaks at {\it both} ends of the
devices that withstand changes in the junction transparencies. The measured
maximum topological gaps in our devices are 20-eV. This demonstration
is a prerequisite for experiments involving fusion and braiding of Majorana
zero modes.Comment: Fixed typos. Fig. 3 is now readable by Adobe Reade