Mapping The Future Of Lithography

The SPIE Advanced Lithography + Patterning (AL+P) Symposium is always an informative event for lithographers, and looking at the Advance Program, it appears that AL+P 2023 will be no exception. The progress being made on key lithographic challenges is consistently of interest to attendees, and there will be many timely presentations that address issues of current significance.

For example, resist capability has been an EUV lithography challenge for many years, and it will be good to see what progress has been made in recent months. Metal-oxide resists have shown promise, and I look forward to finding out if these materials are now finally being used in high-volume manufacturing. It will be good to see the status of the more recently introduced EUV resists that are deposited in vacuum. Perhaps we will also see new and novel resist technologies that could provide solutions for leading-edge lithography. People are starting to study the resist development process more closely, and I look forward to seeing what new things have been learned recently. Higher exposure dose requirements for EUV resists have been projected, and it will be interesting to see if the latest results confirm or refute those projections. During past conferences, the importance of resist-underlayer interactions was identified. This year, there are several papers on this topic, so it will be nice to see if this has become better understood, and if good underlayer solutions have been found for particular resists.

Because of mask 3D effects, the computational aspects of EUV lithography are proving to be particularly challenging and complex, and it will be interesting to see what progress has been made on that front. Have greatly improved absorber materials been identified for EUV masks, perhaps attPSM, that will reduce the problem of mask 3D effects? Even for optical lithography, there are still computational challenges. Are more companies now extending optical lithography and improving yields by applying inverse lithography technology (ILT) to full chips?

The application of ILT has led naturally to the introduction of curvilinear features on the mask. This year, a paper by authors from imec will describe the extension of curvilinear features to the design. The introduction of curvilinear and curvy features is accompanied by a host of new problems in need of solution. Is the industry converging on data formats for curvy features? For line/space patterns, we have long used the concept of critical dimension for process control and design rules, and even this concept has become complex when we take line-edge roughness into account. For curvy features, what metrics will we use to characterize dimensional control? Will robust methods be found for debiasing SEM measurements of curvy features in the presence of edge roughness?

As we get closer to the date that ASML projected for having the first high-NA EUV exposure tool operational, it will be interesting to see if they have been able to maintain their schedule. ASML has recently said that they are looking into EUV exposure systems with NA ≥ 0.75; perhaps we will hear something substantial at AL+P about their plans? Will we see a transition to a 300-mm round format for EUV masks?

As the editor-in-chief of SPIE’s Journal of Micro/Nanopatterning, Materials, and Metrology (JM3), I am always on the look-out for material that could be the basis of a good paper for JM3. Interesting technical material is essential, but authors who can write well are also needed.

There will be papers from both Multibeam and Nikon about direct write lithography tools, one using e-beams and the other being optical. People have been talking about direct write lithography for many years, so it will be nice to get updates from equipment companies who seem to be getting closer to making this approach a reality.

The group of plenary speakers looks particularly strong, and I look forward to hearing their perspectives and insights on lithography and the semiconductor industry.

There are many abstracts in the Advance Program for AL+P 2023 that look interesting, so many, in fact, that I will not be able to hear live all of the papers in which I am interested, due to conflicts between parallel sessions (something that even the much-improved conference app cannot solve). I expect to be viewing quite a few video recordings during the week following the Symposium. Finding so many conflicts among the papers speaks to the quality of AL+P as a conference.

Important components of every AL+P Symposium are the interactions we have with our fellow patterning technologists. These include discussions with long-time colleagues, but it also nice to meet new people, particularly the young engineers who will continue the advancement of lithography in years ahead. Last year’s AL+P symposium was a face-to-face meeting, but few of our colleagues from Asia were able at attend because of lingering Covid restrictions. I look forward to this year’s symposium, where much more of lithography community world-wide will be able to come together.