40th EMLC Honors Three Decades Of Vision From Dr. Uwe Behringer

The European Mask Lithography Conference (EMLC), an annual event that brings together researchers from around the world to present the latest findings on photomask and lithography technology, returned to Dresden from June 16 to June 18, 2025, and took place for the 40th time – marking a memorable anniversary combined with a premiere. For over 30 years, Dr. Uwe Behringer shaped the conference as Conference Chair. Starting this year, Ines Stolberg (Vistec Electron Beam) and Jo Finders (ASML) have jointly taken over the leadership of the conference, while Hans Löschner (IMS Nanofabrication) continues to fill the role of Program Chair.

40 years of EMLC and 30 years of leadership by Dr. Behringer – all a good reason for a brief review.

EMLC was first held in Munich in 1986, as a more or less national meeting of scientists and engineers from the semiconductor industry, and has been held every year since. In 1993, Dr. Behringer became Conference Chair and led the conference step by step to its current position as one of the world’s three leading conferences on mask and lithography technology – in close partnership with the organizers of the other two annual conferences, SPIE Photomask Technology (Monterey, USA) and Photomask Japan (Yokohama).

Important stages on this path, also initiated by Dr. Behringer, were the change of the conference language to English in 1996 and the organization of the conference not only in Germany in Munich and later in Dresden, but also in other European centers of the semiconductor and nano-industry, including Grenoble (France), Eindhoven (Netherlands) and Leuven (Belgium). The most important factor in the success of a conference, and one that was significantly influenced by Dr. Behringer’s work, is of course the quality of the conference program and the invited keynotes, not forgetting the legendary conference dinners. For his extraordinary services to this conference, Dr. Behringer was appointed Honorary President for life and honored in a special contribution at this year’s conference.

Left: Dr. Uwe Behringer; middle: Ines Stolberg; right: Jo Finders.

EMLC 2025 featured 15 sessions with 30 presentations, 22 posters, 4 keynotes and 6 student presentations, which were also shown as posters.

In the keynotes from ESMC, GlobalFoundries, Infineon and Zeiss, the audience gained an insight into the ongoing construction projects at the Dresden site and current technological developments. The presentation by ESMC (a joint venture between TSMC, Bosch, Infineon and NXP) showed very clearly and practically the effort and meticulousness required to get a semiconductor factory up and running and, thanks to the European Chips Act, we can once again observe this in Central Europe.

The keynote from Zeiss presented an overview of the theoretical and technological challenges to be overcome in order to achieve the promised performance of the latest lithography technologies, including High-NA EUV (13.5 nm wavelength of the light used and 0.55 numerical aperture of the optical system). To quote an example from the presentation about the scale of the challenges: In the mid-1980s, when this conference first took place, the necessary optical bandwidth of the most powerful lithography devices was around 1 megapixel per mm². Today, this value is around 10 gigapixels per mm² – i.e. 10,000 (!) times more objects have to be reliably imaged on the same surface area than approximately 40 years ago. This describes the current requirements for the physics and chemistry of these technologies quite clearly, and the other presentations and posters were dedicated to this in detail.

Lithography almost always starts with the production of a mask, for which electron multibeam pattern generators are primarily used today. Several contributions presented the 4th generation of devices from IMS Nanofabrication and NuFlare Technology, and showed how the requirements for the A7 technology node (i.e. the smallest line widths of approx. 5 nm) can be met through smaller pixel sizes and many other detail improvements.

The physics of EUV and electron beam equipment is one challenge; the chemistry of resists and other materials is another, which must be mastered again and again – and so a number of presentations and posters again dealt with the topic of extending the limits for achievable structure sizes and line-edge roughness by means of smaller molecules and better EUV absorption. The current headlines here are dry resist, metal oxide resist and multi-trigger resist, for which further details can easily be found in the relevant literature.

A question that has been discussed repeatedly at mask conferences in recent years now seems to be close to a solution: for High-NA technology it is necessary to use so-called anamorphic optics (i.e. the structures on the mask are enlarged by a factor of 4 in one direction, but by a factor of 8 in the other). This can mean that very large chips that used to fit on a mask no longer fit. There are two possible solutions: either the masks are also made larger by a factor of 2 in one direction, or the structures of a chip are patterned on two masks and then placed on the wafer with two successive exposures. It is clear that the areas where the structures meet are prone to defects. A paper by ASML has shown that the two structures can be stitched together without defects if the masks are suitably designed. This will probably put an end to the discussion about the need for a new mask format for the time being.

Now that High-NA technology is getting ever closer to being introduced in high-volume manufacturing, intensive work is of course also being done on the follow-up technology (Hyper-NA, NA=0.75). A contribution from ASML has beautifully illustrated the imaging quality that will be possible for the A10 and A7 technology nodes in the future.

Traditionally, the conference is also dedicated to other maskless lithography technologies such as direct writing with electron beam or laser writers, nano-imprint and, as a variant of laser direct writing, two-photon lithography. For example, two contributions from Jenoptik GmbH and Fraunhofer ENAS dealt with the efficient production of optical metamaterials and components for quantum computers using VSB electron beam writers.

Several contributions and posters also dealt with the modeling and application of two-photon lithography, which opens up new possibilities, especially for the production of 3-dimensional nanostructures, due to its high imaging contrast. A contribution from this topic group entitled “Physics based deep learning network for direct laser writing two photon polymerization lithography”, presented by Valeria Sedova, was honoured with the “Zeiss Award for Talents in Photomask Industry”, which is awarded to the best contribution in the Students Session.

The award for the best contribution to EMLC 2025 went to the presentation by Joost Bekaert et. al, called “High-NA EUV Mask CD-SEM Metrology Matching, and Contour-based Comparison of Simulation Result and Wafer Print”.

Traditionally, the get-together on the evening of the first day of the conference and the conference dinner on the evening of the second day are also among the highlights of the conference. Once again this year, the conference dinner was held as a river cruise with a steamer on the river Elbe, making it a memorable affair for participants to enjoy for personal discussions with colleagues.

The next EMLC will take place in June 2026 in Jena, the home of Carl Zeiss and Ernst Abbe, the fathers of science-based optical instrumentation. To sign up to receive information on next year’s event once it becomes available, please contact https://www.emlc-conference.com/en. We hope you will join us!