Lithographie à faisceau d'électrons

L'utilisation d'un faisceau d'électrons pour tracer des motifs sur une surface est connue sous le nom de lithographie par faisceau d'électrons. On parle également de lithographie électronique. Par rapport à la photolithographie, l'avantage de cette technique est qu'elle permet de repousser les limites de la diffraction de la lumière et de dessiner des motifs avec une résolution pouvant aller jusqu'au nanomètre. Cette forme de lithographie a trouvé diverses formes d'application dans la recherche et l'industrie des semi-conducteurs et dans ce qu'il est convenu d'appeler les nanotechnologies. Vue d'ensemble La lithographie électronique implique un faisceau d'électrons qui doit être adressé précisément dans la zone que l'on veut impressionner. Bien que des concepts de projection analogues à ce qui est pratiqué en photolithographie aient été explorés, il s'agit, en pratique, d'un procédé purement sériel, nécessairement long, comparé à une technique parallèle comme la projection

Electron Beam Induced Copper Deposition from Carboxylate Precursors and the Study of Underlying Growth Mechanisms

Luisa Berger

The fabrication of defined and high-quality metal nanostructures is an ongoing topic of research. Direct-write deposition of copper nanostructures is of great value for many fields of research and industrial applications. Focused electron beam induced deposition (FEBID) is an additive fabrication technique with extremely high resolution and versatility. Physisorbed, gaseous precursor molecules are locally dissociated by a finely focused electron beam resulting in volatile fragments which desorb and non-volatile fragments forming the deposit. When applying suitable deposition parameters, these deposits can be as small as the beam diameter and have ideally little to no contamination. For electron beam induced metal deposition, metal-organic compounds are chosen as precursors. However, organic ligand material is often co-deposited, which is detrimental to the depositâs properties. This work addresses the study of the perfluorinated copper carboxylate [Cu2(ÎŒ-O2CC2F5)4] (Cu2(pfp)4) and its aminated derivatives Cu2(EtNH2)2(pfp)4 and Cu2(tBuNH2)2(pfp)4 as viable FEBID precursors. 25 at.% of copper was achieved with the amine free compound, and 15 at.% with each of the two aminated complexes. Based on the chemical analysis of the deposits, electron-induced dissociation paths were proposed for the adsorbed species, demonstrating the influence of the ligand chemistry and fragmentation on the deposit composition. In parallel, the perfluorinated silver carboxylate Ag2(pfp)2 was reported and compared directly to its copper equivalent. The silver complex yielded up to 74 at.% metal content and exhibited strong susceptibility to varying electron beam densities throughout the deposit. Cu2(pfp)4 did not manifest the same electron sensitivity. Theoretical models, combining analytical solutions with Monte Carlo simulations of primary and backscattered electrons were successfully fitted to the cross sections of deposits from both carboxylates, determining the growth regimes within a single spot deposit. Additionally, two previously reported Î²-diketonates, Cu(hfac)2 and Cu(tbaoac)2, were directly compared to the other Cu(II) precursors with the aim to determine any dependence of the ligand size, electron density or dwell time on the deposit purity. The investigations concluded that the metal content rather depends on the chemistry of the metal-ligand bond than on the ligand size. This applies to both, the variation of ligands and the variation of the metal center. vii Furthermore, two copper complexes, Cu(hfac)2 and Cu2(pfp)4, were investigated in situ with a dedicated, custom-made setup. The âeQCMâ combines a low energy electron source (10- 100 eV) with a quartz crystal microbalance and serves to study fundamental processes occurring during FEBI deposition. First results yielded the total dissociation cross section for each precursor at varying electron energies. Finally, alternative approaches for the electron induced copper deposition from Cu2(pfp)4 were investigated. A two-step post-purification recipe of as-deposited material was reported to yield pure copper crystals (> 97 at.%). Additionally, direct electron beam lithography in a layer of condensed precursor was explored. This room temperature deposition approach yielded in lower metal contents but could potentially produce high resolution deposition.

EPFL2020

Nano-SAW Devices for Wireless Identification

Florian Bienefelt

Surface Acoustic Wave (SAW) technology is omnipresent in the devices around us today, mainly used as passive bandpass filters in most radio systems like smartphones and TV antennas or as delay lines in telecommunications. More recently, the possibility to use SAW devices for wireless identification has surfaced and generated the first widespread applications such as on the highways in Norway over 2 decades ago. Their environmentally robust structure and passive use is very interesting for many applications in outdoor environments or chemically challenging places. It is possible to read many of them simultaneously and the amount of information that can be carried is much higher than printed barcodes. This semester project was aimed at learning how to design and fabricate an RFID device based on SAW technology in a cleanroom and trying to optimize the parameters of the device while reducing its size. Optical lithography tools with feature sizes down to 2 μm will help achieve this before E-Beam lithography can further decrease the features in scale of the structures involved in a SAW RFID tag. While creating an entire working wireless tag would take more time than available, the objective is to take this project as far as it can to pave the way for future students to search on this topic and increase knowledge about SAW devices.

2014

High robustness of correlation-based alignment with Penrose patterns to marker damage in electron beam lithography

Correlation-based alignment is an alternative alignment method for electron beam lithography. Using complex marker patterns, such as Penrose patterns, which contain more positional information, greater alignment accuracy can be achieved. Correlation-based alignment with Penrose patterns is less susceptible to marker edge defects, such as rat bites, roughness and flagging, since many more edges contribute to determining the marker position. There are however other defects associated with fabricating markers and this paper investigates how defects that result in parts of the pattern being omitted or obscured affect the correlation process when using Penrose pattern markers. We show that in both cases severely damaged markers can be used successfully and demonstrate fabricated structures with sub-5 nm alignment using markers with up to 80% of the marker pattern missing. (C) 2008 Elsevier B.V. All rights reserved

Elsevier2009

Electron Beam Induced Copper Deposition from Carboxylate Precursors and the Study of Underlying Growth Mechanisms

Luisa Berger

EPFL2020