Mask Based Lithography for Fast, Large Scale Pattern Generation with Nanometer Resolution

Periodic Reporting for period 3 - Nanolace (Mask Based Lithography for Fast, Large Scale Pattern Generation with Nanometer Resolution)

Reporting period: 2022-07-01 to 2023-08-31

Problem/issue being addressed:

Lithography refers to the transfer of a pattern onto a substrate. Lithography techniques are used in the production of a huge range of devices and materials ranging from microelectronics and MEMS devices to optical metamaterials and smart surfaces for medical and other applications. The ultimate goal and limit of lithography is to obtain fast and large scale patterning which enables the controlled positioning of individual molecules or atoms. This requires fast, large scale single nm resolution patterning. At the moment no techniques are available that can do that. Fast positioning of individual molecules or atoms over large areas can path the way for the creation and industrial application of whole new classes of materials and devices including room temperature quantum electronic devices, electronic metamaterials as well as nano filtration membranes and can push the performance of todays microelectronics. The highest resolution fast, large scale lithography technique today is photolithography where a photon beam is projected through a mask, so that the pattern from the mask is replicated by direct imaging on a substrate coated with resist. Next generation Extreme UltraViolet (EUV) lithography uses 92 eV photons and is targeted to deliver 8 nm resolution. The EUV ultimate limit, determined by the secondary electron generation blur, is estimated to be around 6 nm, which does not enable single nm resolution patterning. Further reductions in the photolithography resolution of the patterning would increase the photon energy, exacerbating the secondary blur.

Why is it important for society?

Nanolace offers the possibility of:

i) industrial scale production of quantum electronic and spintronics devices, where operation at room temperature requires that two or all of the device dimensions are less than 5 nm;
ii) making electron meta-materials, a whole new class of materials that are the electronic counterpart to optical meta-materials;
iii) producing nanomembranes with holes in the range 1-10 nm, to be used for example for nanofiltration;
iv) addressing the ongoing miniaturisation need of today’s microelectronic;

Overall objectives:

The aim of the Nanolace project is to demonstrate mask-based lithography with 1 nm resolution in two different ways, which “fit together”. In order for mask-based lithography with 1 nm resolution to become truly important it is necessary to be able to do two things: i) Fast prototyping of many different patterns and ii) mass production of selected patterns for further device production. The fast prototyping will be done by demonstrating lithography with bose Einstein condensated atoms using an optical mask (which can be very quickly reconfigured, just upload a new image) and mass production using a beam of metastable helium atoms, and a solid state “hole-structure” masked designed using near field binary holography, an idea published by consortium members in 2019 (T. Nesse, I. Simonsen, B. Holst, Nanometer-Resolution Mask Lithography with Matter Waves. Near-Field Binary Holography, Phys. Rev Applied 11, 024009 (2019).

The first project period ran from January to December 2020. The project was hard hit by the Covid-19 crisis, which lead to substantial delay for all project partners. That said major progress has been made on the design and construction of the two lithography instruments. First masks were also successfully produced with a pitch of 50 nm and a hole size of 25 nm, which should enable patterns with a resolution of 50 nm to be generated, potentially more.

Progress beyond the state of the art until the end of the project:

The expected progress beyond state of the art untill the end of the project is in line with the originall aim of the Nanolace project: To perform for the first time: mask-based lithography with 1 nm resolution. Two different approaches are foreseen: The fast prototyping will be done by demonstrating lithography with bose Einstein condensated atoms using an optical mask (which can be very quickly reconfigured, just upload a new image) and mass production will be done using a beam of metastable helium atoms, and a solid state “hole-structure” masked designed using near field binary holography, an idea published by consortium members in 2019 (T. Nesse, I. Simonsen, B. Holst, Nanometer-Resolution Mask Lithography with Matter Waves. Near-Field Binary Holography, Phys. Rev Applied 11, 024009 (2019).

Expected results until the end of the project:

1) To develop two novel resists and etch protocols that enables 1 nm
resolution patterning with metastable helium atoms (He*) (patterning resist) and rubidium (Rb) BEC (forming
patterned hard mask, or direct substrate etch);
2) To make solid state masks for 1 nm resolution patterning with He*;
3) To construct a He* lithography instrument for testing the masks and resist;
4) To make optical masks for 1 nm resolution pattering with Rb;
5) To construct a BEC lithography instrument for testing the masks and etch protocol;
6) To extend the theoretical framework for mask calculations to increase the write field (i.e. the surface
area that can be addressed in a single exposure);
7) To generate patterns by mask atom lithography with 1 nm resolution and an initial write field of 50 μm diameter (not a theoretical limit).

Potential impact including socio-economic impact:

Nanolace will make it possible to do industrial scale production of devices, where two or all of the device dimensions are less than 5 nm;
and producing nanomembranes with holes in the range 1-10 nm. During the past ten to fifteen years the EU has taken a leadership role in both research and commercial
development of lithography. EU lithography tool vendor ASML is the world leader for commercial tools. Innovative new lithography technologies from EU companies, such as multiple electron beam lithography and thermal scanning probe lithography
amongst others, together with the high investment of the EU commission to support research projects in this field, demonstrate the strong interest of the EU in this topic. Nanolace breakthroughs will strengthen the leading position of Europe in the lithography industry, supporting EU policies on EU competitiveness and innovation.

The increase in the capability of computer processors and their improved power performance and efficiency thanks to the introduction of quantum electronic devices will ultimately simplify or enhance consumers’ lives, who are increasingly connected to information at all times, and remove one of the biggest obstacles holding back the Internet of Things and wearable computing, namely: poor battery performance. Moreover, the miniaturisation of electronic devices thanks to Nanolace will satisfy consumer’s increasing demand of smart, small and light wearable devices. The application of Nanolace for the production of nanomembranes for energy efficient de-salination has the potential of a huge societal impact. The UN Sustainable development goal calls for universal access to drinking water. According to the International Water Organisation around 1% of the world’s drinking water is currently
provided by desalination. Desalination is a particularly attractive mean for providing water in the long term, because over 50% of the world population lives in urban centres bordering the ocean and, in many parts, including
Northern Africa the population concentration along the coast exceeds 75%.

SEM micrograph of 2-micron square regions containing a square array of 50 nm period holes

Periodic Reporting for period 3 - Nanolace (Mask Based Lithography for Fast, Large Scale Pattern Generation with Nanometer Resolution)

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