Expert Interview: Bruno La Fontaine

[00:00:00] Theresa Duque:

Hi, this is Theresa Duque from Berkeley Lab’s Strategic Communications Team. I’m here today with Bruno La Fontaine, who joined Berkeley Lab in 2023 to lead the Center for X-Ray optics, also known as CXRO.

Before joining Berkeley Lab, he worked as a researcher in the semiconductor industry, collaborating with scientists at CXRO and the Advanced Light Source, a synchrotron user facility at Berkeley Lab. That foundational work carried out at CXRO helped pioneer a revolutionary technique called extreme ultraviolet lithography.

The breakthrough has enabled record-breaking microchips for smartphones, smart homes, and more. Welcome, Bruno.

[00:00:48] Bruno La Fontaine:

Good morning, Theresa. Pleasure to be here with you.

[00:00:51] Theresa:

To get things started, I’d like to begin with the basics.
What is extreme ultraviolet lithography?

[00:00:59] Bruno:

Lithography is a technique that is used in microelectronics manufacturing to produce very small features on a silicon wafer. Essentially, it’s an imaging technique. You start with a pattern that is what we call a mask. And that mask has patterns that you want to have on a certain circuit on your chip. It could be part of a transistor or some interconnect pattern to conduct electricity, bring power to the various components, and that mask basically is imaged onto a silicon wafer using some optics.

The EUV part or extreme ultraviolet is all about making these patterns smaller, using shorter wavelength. When the light has a shorter wavelength, it can basically resolve smaller patterns. So let me give you the example of the previous generation of lithography, which was called Deep UV or DUV. The wavelength used for that was 193 nanometer.

When we go to EUV, the wavelength goes down all the way to 13.5 nanometer, so it’s more than 10 x reduction in wavelength. And with that comes essentially the same factor improvement in resolution, meaning smaller features. Going from DUV to EUV, people were able to reduce the size of the feature and reduce the size of the chips.

You can put more patterns, more circuit elements, more transistors. And as you drive this performance you use less energy.

[00:02:43] Theresa:

So Bruno, how are national labs and Berkeley Lab in particular uniquely positioned to contribute to advancing EUV lithography?

[00:02:52] Bruno:

Back in the 1990s, there was this effort around the Bay Area, mainly, where some companies — Intel, one of them, AMP, Motorola — together made a limited liability company, the EUV LLC — and they contracted with national labs, so Berkeley Lab, also Lawrence Livermore Lab and Sandia Lab in Livermore — to develop this technology. That was a big effort in those days, and the labs in this effort collaborated together and were called the Virtual National Lab — VNL. So Berkeley Lab was involved as early as the ’90s in this effort to develop EUV lithography — and has been involved in the development of EUV lithography ever since.

[00:03:46] Theresa:

Let’s talk about the Advanced Light Source, because I hear that the Advanced Light Source played a key role in helping develop EUV lithography.

[00:03:55] Bruno:

Yeah, most definitely. So, in the ’90s, it would’ve been very difficult to do all the studies that we did without having a synchrotron. The Advanced Light Source synchrotron is a very reliable source of soft X-rays or extreme ultraviolet. It has the properties that are similar to that of a laser.

A laser is essentially a very small source of light that also propagates light over long distances. And so synchrotrons are very much like that. And when you have this, you can develop optical techniques, which CXRO did together with the ALS, controlling this light, shaping it to use it to enhance the imaging properties of our micro-exposure lithography tools. So that’s a unique property that, in the ’90s, there was no source really that outside of synchrotrons that could do this.

[00:04:55] Theresa:

How will the Advanced Light Source upgrade help in advancing EUV lithography in the future?

[00:05:01] Bruno La Fontaine:

The upgrade of the ALS will make the light beam even more intense.
It will make it brighter and more coherent. And that means, even more like a laser. And then when you do this for lithography, it allows us to manipulate those wavefronts even more and tailor them to specific types of imaging. So if your pattern for your circuit is a certain way, it might benefit from having a beam of light strike the mask or the pattern that you want to image at a certain angle, in a certain way, and some other patterns will be different. So the ability to manipulate very precisely, this will help the imaging quality and the future commercial tool will have better coherence, also a better ability to manipulate this. So having the ALS-U will enable us to study how much better this can be.

[00:06:03] Theresa:

Bruno La Fontaine, thank you so much for sharing your perspective with us.

[00:06:08] Bruno:

Was very much a pleasure for me. Thank you.

[00:06:12] Theresa:

You can learn more about the Advanced Light Source by going to als.lbl.gov. Learn more about the Center for X-ray Optics by going to cxro.lbl.gov. For Strategic Communications at Berkeley Lab, I’m Theresa Duque.