Chapter 1614 If God closes a window for me, then he will just lift the roof off

at the same time.

Torch Laboratory, underground testing center.

Since witnessing the existence of macroscopic negative refractive lenses a month ago, the work direction of Zhang Runing's research team has undergone a fundamental change.

Due to the strictest confidentiality requirements, everything seems to be normal at the Changguang Group headquarters, and the ArF-1800 project is still being advanced along the original reciprocal route.

However, in reality, those thick design manuals, which condensed countless efforts, have been quietly locked in the deepest filing cabinet.

Zhang Runing himself led a group of the most core and reliable technical backbones and moved directly to the capital to start work.

This time, the Torch Laboratory generously lent out part of its space to enable close collaboration with the Changguang project team.

The reason why we didn’t allow the Lianhai Institute of Chemistry to send anyone over here was because we didn’t want to reveal the secret of the negative refractive material.

As for Zhang Runing, there is naturally no such concern.

After all, he is the core designer of the lithography system.

However, collaboration is collaboration.

A mere month is not enough time for either side to come up with any big news.

The presence of negative refractive materials does simplify the light path distribution inside the objective system, but for each set of transmission/reflection elements itself, there are more parts that need to be paid attention to.

Moreover, the manufacture and wafering of Ga-Ge (0001) is inherently difficult, and the lens group cannot contain only plane mirrors.

How to make this new thing into a curved mirror also consumed a lot of energy of Chang Haonan and Li Yabo.

And now is the time to test the results.

Everyone's eyes were focused on the center of the experimental table.

There is a high-precision Twyman-Green laser interferometer placed there.

Judging from the reserved holes in the lens holder, what is about to be tested is a three-lens system.

The fused quartz lens at position 1 and the lithium barium fluoride lens at position 3 have been installed in place.

Only position number two is left vacant.

It will also be the core that determines the success or failure of this critical experiment.

A few minutes later, the lab's airtight door slid open.

Li Yabo appeared at the door, holding a transparent dust-proof protective box in his hand.

Every step taken is cautious.

"Researcher Zhang, the basic tests have been completed."

He placed the box steadily in front of Zhang Runing.

Inside the box is a lead-gray convex lens.

Fixed by a special clamp.

It is lens No. 0001 made of Ga-Ge ().

Zhang Runing leaned over and observed carefully for a moment.

"The material preparation is quite difficult, so the thickness of this lens is about 65% smaller than originally expected."

Li Yabo paused and added:

"But we have repeatedly tested its basic optical performance in a variety of ways to confirm that it meets the requirements of the system design."

In fact, generally speaking, as long as the optical performance remains consistent, the lens thickness should be thinner.

But this piece is a bit too thin...

So much so that even the operation requires special attention.

Zhang Runing nodded:

"understand."

This is definitely not a compliment.

He was very satisfied to be able to get a sample of this size at this point in time.

As he spoke, he waved his hand again, signaling his assistant He Xiujun behind him to start work.

The latter stepped forward and opened the dedicated operating glove interface of the protective box.

Zhang Runing personally put on special protective gloves and put his hands into the box.

In order to facilitate handling and provide protection, the lens is actually covered with a hard shell.

But even so, it still feels almost unreal.

Unfasten the clamp.

Remove the lens.

Slowly place it on the second position of the bracket.

With a slight "click" sound, the magnetic clamp is firmly attached.

Return.

Finally, remove the protective cover.

"Get ready to record." Zhang Runing's voice was steady and powerful, breaking the silence of the laboratory.

"Start the interferometer and set the wavelength of the light source to 486.1nm (F line, hydrogen blue light) as the base reference wavelength."

He Xiujun quickly took over the control console.

The laser emits crystal blue light, which passes through a beam splitter to form two coherent light paths.

One beam passes through a three-lens system and the other serves as a reference.

The interferometer's optical platform made a subtle adjustment sound.

A few seconds later, He Xiujun stared at the interference pattern generated in real time on the high-resolution display.

The report said:

"Engineer Zhang, the fringes have been adjusted to zero! At the reference wavelength, the system's wavefront aberration is extremely small and in perfect condition!"

"Okay." Zhang Runing's tone was almost unchanged. "Begin scanning! Start with a wavelength of 486.1nm (hydrogen blue line F) and gradually move towards the short-wave direction."

"understand!"

He Xiujun opened the test program that had been written long ago and let the laser adjust its output automatically.

On the display screen, the light and dark stripe pattern formed by the interference and superposition of two beams of light changes slightly with the change of wavelength.

Everyone's hearts were in their throats.

435.84nm……(mercury blue line g)

404.66nm……(mercury violet line h)

365.01nm……(mercury ultraviolet I)

The wavelengths are getting shorter and shorter, gradually approaching the deep ultraviolet (DUV) region.

This is the wavelength band where the dispersion of traditional optical materials increases dramatically and aberrations are most difficult to control.

However, although the interference fringes on the screen showed slight fluctuations as the wavelength changed, the magnitude of the changes was almost invisible to the naked eye.

If traditional optical devices are used, perhaps only Zeiss can achieve a similar level.

And it would certainly require a huge and complex lens system.

It is definitely not something that can be solved with just three lenses.

"It's so stable..." an optical engineer from Changguang couldn't help but exclaimed in a low voice.

Li Yabo had anticipated this result, but when he saw it with his own eyes, he couldn't help but smile.

If this achievement is successfully put into use, even his own title of academician can be put on the agenda.

Under normal circumstances, when there are two academicians in a course, the student will usually be in the same academy as the teacher.

But his teacher is also a member of two academies.

Oh, how should I choose then?

What a painful decision...

……

Just when Li Yabo could no longer resist his wild thoughts, He Xiujun's excited voice came over:

"The data is out!"

He wanted to put his head into the screen:

"Compared to the reference wavelength, the RMS value (root mean square) of the system wavefront has increased by... less than 0.15!"

In practical applications, the width of the DUV light source is very narrow and it is impossible to cover such a wide range from 486.1nm to 193nm.

Therefore, when this value is converted to the lithography machine, it is already a very excellent result.

Another engineer behind him shuddered:

"This... This is much more stable than any of our previous all-refractive or catadioptric systems in this wavelength range!"

Zhang Runing pursed his lips and said nothing, but his clenched fists loosened slightly and his shoulders drooped a lot.

However, it is not time to completely relax yet.

On the computer screen, the interference fringes at the ArF wavelength are still clearly visible.

Although slightly thicker than at longer wavelengths, the overall shape is well maintained without catastrophic collapse.

“Extract the Zernike coefficients and focus on analyzing the defocus term Z4!”

Zhang Runing spoke faster.

The Zernike coefficients are a standard mathematical tool for quantifying the aberrations of an optical system.

The Z4 term represents defocus, which is one of the core aberrations caused by dispersion.

He Xiujun operates the software skillfully to collect and analyze the current interference pattern at high speed.

After more than ten seconds, the result popped up!

"The Z4 value is... -0.042λ."

He Xiujun's voice was shrill due to his excitement:

"Compared to our most successful achromatic solution, the measured Z4 value of this three-lens system at the same focal length is reduced by almost one-third..."

Reducing it by one third is a big deal.

But that’s not the most important thing.

“Moreover,” Zhang Runing added, “the volume of this system is less than one-fifth of the traditional achromatic component!”

A more compact size and simpler structure are equivalent to leaving a higher degree of freedom for other parts of the objective lens group.

Obviously, they succeeded.

This isn’t just a triumph of data.

Or it opens a window of hope for breaking through ASML's blockade of lithography technology...

wrong.

It's more than just opening a window.

This is blowing the roof off the house...

Just as everyone was immersed in the joy of initial success, the airtight door slid open again.

A tester poked his head in and said, "Professor Li, there's a phone call from Academician Chang."

Li Yabo, who was discussing the results with several other people, was stunned and then left in a hurry.

But just a few minutes later, it was gone and back again.

"Everyone!" Li Yabo interrupted the discussion and celebration. "Academician Chang asked me to notify everyone immediately and gather in the top floor conference room as soon as possible!"

The smile on Zhang Runing's face instantly faded, and he became serious:

"Professor Li, what's the hurry?"

He looked at the equipment beside him and the data on the computer screen: "There are still some finishing touches and repeated verifications in the experiment...Does everyone need to go over there?"

"The teacher said that he found a completely new theoretical method!"

Perhaps because of the long run, Li Yabo's breathing was a little rapid:

“It can replace the existing system to describe and theoretically explain polarization aberration.”

As soon as these words were spoken, even He Xiujun, who was sitting in front of the computer analyzing data, stopped what he was doing and turned to look at Li Yabo.

"Alternative Jones Matrix?"

More than one person blurted out.

In the imaging process of traditional optical systems, light is mostly treated as a scalar and its vector characteristics are ignored.

However, in projection lithography objectives, as the numerical aperture NA continues to increase, the vector characteristics of light will gradually have a greater impact on the imaging effect.

Especially for systems such as 3G immersion fluid and lutetium aluminum garnet whose NA value is expected to be greater than 1.70, traditional scalar aberration theory is no longer sufficient to fully characterize the imaging performance of the optical system.

Polarization aberration theory must be used.

However, there is not even a perfect description form for polarization phase difference, and the Mueller matrix and Jones matrix each have their own range of inapplicability.

If this problem can be solved, it will undoubtedly fill a gap in the field of ultra-high precision imaging.

Zhang Runing made a decision instantly:

"Stop all experimental operations at hand and lock the equipment status!"

"Xiao He, be sure to save all the data."

"Everyone, follow me upstairs!"