Approaching the Resolution Limit of Nanometer-Scale Electron Beam-Induced Deposition

Dorp, Willem F. van; Someren, B. van; Hagen, C. W.; Kruit, P.; Crozier, Peter

doi:10.1021/nl050522i

Cited by 256 publications

(253 citation statements)

References 9 publications

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“…At the opposite extreme, manipulation of individual atoms at low temperatures using a scanning tunneling microscope (STM) ensures the finest resolution but has a very slow writing speed. [20] with the addition of results obtained by van Dorp et al [21] with e-beam induced deposition (EBID)). Adapted from [20].…”

Section: Nanolithographymentioning

confidence: 99%

Resists for sub-20-nm electron beam lithography with a focus on HSQ: state of the art

2009

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In the past decade, the feature size in ultra large-scale integration (ULSI) has been continuously decreasing, leading to nanostructure fabrication. Nowadays, various lithographic techniques ranging from conventional methods (e.g. photolithography, x-rays) to unconventional ones (e.g. nanoimprint lithography, self-assembled monolayers) are used to create small features. Among all these, resist-based electron beam lithography (EBL) seems to be the most suitable technique when nanostructures are desired. The achievement of sub-20-nm structures using EBL is a very sensitive process determined by various factors, starting with the choice of resist material and ending with the development process. After a short introduction to nanolithography, a framework for the nanofabrication process is presented. To obtain finer patterns, improvements of the material properties of the resist are very important. The present review gives an overview of the best resolution obtained with several types of both organic and inorganic resists. For each resist, the advantages and disadvantages are presented. Although very small features (2-5 nm) have been obtained with PMMA and inorganic metal halides, for the former resist the low etch resistance and instability of the pattern, and for the latter the delicate handling of the samples and the difficulties encountered in the spinning session, prevent the wider use of these e-beam resists in nanostructure fabrication. A relatively new e-beam resist, hydrogen silsesquioxane (HSQ), is very suitable when aiming for sub-20-nm resolution. The changes that this resist undergoes before, during and after electron beam exposure are discussed and the influence of various parameters (e.g. pre-baking, exposure dose, writing strategy, development process) on the resolution is presented. In general, high resolution can be obtained using ultrathin resist layers and when the exposure is performed at high acceleration voltages. Usually, one of the properties of the resist material is improved to the detriment of another. It has been demonstrated that aging, baking at low temperature, immediate exposure after spin coating, the use of a weak developer and development at a low temperature increase the sensitivity but decrease the contrast. The surface roughness is more pronounced at low exposure doses (high sensitivity) and high baking temperatures. A delay between exposure and development seems to increase both contrast and the sensitivity of samples which are stored in a vacuum after exposure, compared to those stored in air. Due to its relative novelty, the capabilities of HSQ have not been completely explored, hence there is still room for improvement.Applications of this electron beam resist in lithographic techniques other than EBL are also discussed. Finally, conclusions and an outlook are presented.

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Section: Nanolithographymentioning

confidence: 99%

Resists for sub-20-nm electron beam lithography with a focus on HSQ: state of the art

2009

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“…This flexibility of the FEBID technique, merged with an enormous downscaling potential [3,4], opens new pathways for various applications such as the development of nano-sensors for magnetic [5,6], strain/ force [1,7], dielectric [8,9] sensing or the possibility to fabricate metallic contact structures with sub-10nm lateral resolution [10]. However, in many cases post-treatment of the as-grown FEBID deposit is inevitable in order to meet the demands for specific applications.…”

Section: Introductionmentioning

confidence: 99%

Identifying the crossover between growth regimes via in-situ conductance measurements in focused electron beam induced deposition

Winhold¹,

Weirich²,

Schwalb³

et al. 2014

Nanofabrication

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Focused electron beam induced deposition presents a promising technique for the fabrication of nanostructures. However, due to the dissociation of mostly organometallic precursor molecules employed for the deposition process, prepared nanostructures contain organic residues leading to rather low conductance of the deposits. Post-growth treatment of the structures by electron irradiation or in reactive atmospheres at elevated temperatures can be applied to purify the samples. Recently, an in-situ conductance optimization process involving evolutionary genetic algorithm techniques has been introduced leading to an increase of conductance by one order of magnitude for tungsten-based deposits using the precursor W(CO)6. This method even allows for the optimization of conductance of nano-structures for which post-growth treatment is not possible or desirable. However, the mechanisms responsible for the observed enhancement have not been studied in depth. In this work, we identified the dwell-time dependent change of conductivity of the samples to be the major contributor to the change of conductance. Specifically, the chemical composition drastically changes with a variation of dwelltime resulting in an increase of the metal content by 15 at% for short dwell-times. The relative change of growth rate amounts to less than 25 % and has a negligible influence on conductance. We anticipate the in-situ genetic algorithm optimization procedure to be of high relevance for new developments regarding binary or ternary systems prepared by focused electron or ion beam induced deposition.

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“…[2][3][4][5][6] This approach can be used to target the generation of extremely small, pure nanostructures with lithographic control, which is one of the main goals in nanotechnology.…”

mentioning

confidence: 99%

“…[3] Organometallic precursors have mostly been used for the generation of metallic nanostructures by EBID. Up to now, the vast majority of EBID experiments were performed in a high vacuum (HV) environment, which results in a typical metal content of only 15 to 60 % in the corresponding deposits (for example, see Refs.…”

mentioning

confidence: 99%

Electrons as “Invisible Ink”: Fabrication of Nanostructures by Local Electron Beam Induced Activation of SiO_x

et al. 2010

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Approaching the Resolution Limit of Nanometer-Scale Electron Beam-Induced Deposition

Cited by 256 publications

References 9 publications

Resists for sub-20-nm electron beam lithography with a focus on HSQ: state of the art

Resists for sub-20-nm electron beam lithography with a focus on HSQ: state of the art

Identifying the crossover between growth regimes via in-situ conductance measurements in focused electron beam induced deposition

Electrons as “Invisible Ink”: Fabrication of Nanostructures by Local Electron Beam Induced Activation of SiO_x

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Approaching the Resolution Limit of Nanometer-Scale Electron Beam-Induced Deposition

Cited by 256 publications

References 9 publications

Resists for sub-20-nm electron beam lithography with a focus on HSQ: state of the art

Resists for sub-20-nm electron beam lithography with a focus on HSQ: state of the art

Identifying the crossover between growth regimes via in-situ conductance measurements in focused electron beam induced deposition

Electrons as “Invisible Ink”: Fabrication of Nanostructures by Local Electron Beam Induced Activation of SiOx

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Electrons as “Invisible Ink”: Fabrication of Nanostructures by Local Electron Beam Induced Activation of SiO_x