# Doctoral Thesis: Electron-beam lithography towards the atomic scale and applications to nano-optics

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Vitor Manfrinato

## Event Location:

36-462 (Allen Room)

## Event Date/Time:

Tuesday, July 28, 2015 - 3:00pm

Abstract:

Electron-beam lithography (EBL) is a high-resolution pattern generation technique widely used in research and development. However, EBL resolution has been limited to 4 nm isolated features and 16 nm periodic structures. Furthermore, the physical mechanisms that limit EBL resolution are not quantitatively clear. The fundamental understanding of the resolution limits of EBL is critically important to push nanotechnology toward the atomic scale.

In this thesis we will show a comprehensive study of the physical phenomena that limit the resolution for EBL at 200 keV. In this study, we investigated the resolution of EBL using an aberration-corrected scanning transmission electron microscope with a 0.15-nm-diameter electron beam as the exposure tool. We achieved isolated features with critical dimensions of 2 nm and 5 nm half-pitch in hydrogen silsesquioxane resist.[1] We analyzed the resolution limits of this technique by measuring the lithographic point-spread function (PSF). Moreover, we measured the delocalized energy transfer in EBL exposure by using chromatic aberration-corrected energy-filtered transmission electron microscopy (EFTEM) at the sub-10 nm scale. We have defined the role of spot-size, electron scattering, secondary electrons, and volume plasmons in the lithographic PSF by performing EFTEM, momentum-resolved electron energy loss spectroscopy (EELS), sub-10 nm EBL, and Monte Carlo simulations.[2] Furthermore, our approach to study the resolution limits of EBL may be applied to other lithographic techniques where electrons also play a key role in resist exposure, such as lower-voltage EBL, ion-beam-, X-ray-, and extreme-ultraviolet lithography. In support of this work, we investigated the impact of plasmonic resonances in metallic nanostructures. We fabricated sub-10 nm plasmonic antennas designed to engineer surface and volume plasmons in the vacuum ultraviolet (VUV) region of the electromagnetic spectrum (3 to 50 eV). The control of volume plasmons may lead to engineering of electron and x-ray losses in advanced resists and novel optical devices in the VUV.

Thesis Supervisor - Prof. Karl Berggren

Committee - Prof. Marc Baldo (MIT)

Dr. Eric Stach (Brookhaven National Lab)

[1] Manfrinato, V.; Zhang, L.; Su, D.; Duan, H.; Hobbs, R.; Stach, E.; Berggren, K., Nano Letters 2013, 13, 1555-1558.
[2] Manfrinato, V.; Wen, J.; Zhang, L.; Yang, Y.; Hobbs, R.; Baker, B.; Su, D.; Zakharov, D.; Zaluzec, N.; Miller, D.; Stach, E.; Berggren, K., Nano Letters 2014, 14, 4406–4412.