Chapter 627: Without foreign technology, can’t we build EUV lithography machines?
"Stuck again?"
After reading Lin Nan's report email, Chen Yansen frowned slightly.
He didn't expect that even though he had kicked the door open and paved the way for them, this group of people were still unable to take another step forward.
The current difficulties are twofold:
First, the aspheric reflector in the relay mirror assembly needs to have a surface accuracy of less than 50 picometers and a surface roughness of less than 0.1 nanometers root mean square error.
In other words, this is equivalent to requiring that the overall undulation of an area the size of Hui'an Province cannot exceed the thickness of an A4 paper.
You can imagine how difficult it is!
At present, only Saigao in the beacon country and Zeiss in Germany have the corresponding level of mirror polishing technology in the world.
However, due to the restrictions of the Wassenaar Arrangement, even if you pay to buy it, you cannot get a supply quota.
Although Harbin Institute of Technology, National University of Defense Technology and Changchun Institute of Optics, Fine Mechanics and Physics of Huazhong University of Science and Technology have ion beam polishing and magnetorheological polishing technologies, which can theoretically achieve atomic-level surface accuracy, there is often a huge gap between reality and theory.
This is like asking, can China produce the engine for an F1 racing car?
Logically speaking, China has no shortage of factories capable of producing metal pistons and cylinders, and is also familiar with the manufacturing principles of internal combustion engines.
However, the F1 racing engine is not a simple combination of single components. It is an integration of cutting-edge technologies such as materials science, precision machining, thermodynamics, and electronic control systems. Its parameter standards for speed, thermal efficiency, and reliability have reached the industry's extreme.
It can be seen from this that even though the technical principles are understood, there is still an insurmountable gap between implementing them in stable actual production.
Understanding it is one thing, creating it is another.
Second, after the mirror is polished, 40 to 60 pairs of alternating thin film layers of molybdenum and silicon must be coated on the surface, and the thickness error of each layer must be controlled at the atomic level.
Although many domestic research institutes have mastered the magnetron sputtering technology required for the coating process, its uniformity and precision still do not meet the requirements for the use of EUV lithography machines.
In addition, how to accurately detect the smoothness of the mirror is also a difficult problem.
No measurement, no processing!
The inspection capability determines the polishing level of the ceiling.
In 2014, China's high-precision interferometers, especially detection equipment and technologies for the EUV band, could not even reach a measurement accuracy of 50 picometers.
Lin Nan, Wang Xiangchao and hundreds of other R&D engineers are already leaders in the optical field. If they can't handle something, it will probably be of no help to ask other people.
They tried their best, but their abilities were limited.
Chen Yansen knew that if he didn't take action, this scientific research battle would most likely become a joke.
After a brief thought, he asked Lin Nan to send him the technical documents of ion beam polishing, magnetorheological polishing and magnetron sputtering.
at the same time.
Shanghai, Xingyuan Technology Optical R&D Center.
Lin Nan leaned against the laboratory table, his eyes bloodshot and his expression gloomy.
Wang Xiangchao sat aside, patted Lin Nan on the shoulder and said, "Don't worry, there will always be a way out when you reach the mountain. Just take your time. Now that we have the plan, why worry about not being able to solve the technical problems?"
An expert from the Shanghai Institute of Optics and Fine Mechanics nodded in agreement, saying, "Before, we didn't need picometer-level polishing precision, so technological progress was slow. Now it's different. As long as we can master the aspheric reflectors for the illumination system, we'll have mastered half of the core technology for the EUV lithography machine's optical system."
Having said that, the atmosphere in the laboratory did not ease much.
Lin Nan gave a wry smile and pointed at the test report on the table. "I understand the logic, but the reality is, our instrument's testing accuracy is only at the sub-nanometer level. We have no idea if the surface accuracy is sufficient."
This is like walking with your eyes closed. You are not even sure whether the direction is right or not. How can you improve?
A young engineer from the Yanjing Institute of Optoelectronics choked up and whispered in despair, "Can't we produce the core components of EUV lithography machines without foreign technical support?"
These words were like a steel needle, piercing everyone's confidence.
"Bullshit! They've spent decades accumulating technology, and we've only been using it for a few days? Don't you even have that much patience?"
Wang Xiangchao stood up abruptly and loudly retorted, "We've come up with a plan for the lighting system in just one month, which proves our approach is correct.
I've already communicated with the people at the Changchun Institute of Optics and Fine Mechanics and the Yenching Institute of Optics and Fine Mechanics. Next, we'll all work together: we'll tackle the projection lens system first. Once the polishing and coating technologies meet the standards, we'll integrate the various technologies. We'll eventually be able to tackle this tough problem."
His words were like a shot in the arm, slightly warming up the depressed atmosphere in the laboratory.
Lin Nan took a deep breath, then stood up and said, "Mr. Wang is right. Let's first divide the work and focus on the optical path design of the projection lens system."
An expert from the Shanghai Institute of Optics and Fine Mechanics immediately pulled out a blueprint and pointed to the complex optical path structure: "The projection objective lens must accurately focus the light beam from the illumination system onto the wafer, and eliminate various aberrations. This requires a higher curvature accuracy for the lens than for the reflector.
The optical path we designed previously still had an aberration deviation of 0.5 arc seconds in the simulation environment, which needed to be optimized."
Wang Xiangchao leaned over to the blueprint and added, "I've looked up information. Zeiss's projection objective lens uses 15 high-precision lenses, and the surface error of each lens is controlled within 20 picometers.
If we can reduce the aberration deviation to below 0.2 arc seconds and keep up with the subsequent technology, we may be able to catch up with their level."
The more they talked, the more engaged they became, and they immediately started busying themselves around the drawings and computers.
Wang Xiangchao was responsible for adjusting the optical path simulation parameters, while Lin Nan led a few people to calculate the correspondence between the lens curvature and aberration. The remaining R&D personnel also quickly suppressed their previous negative emotions and quickly devoted their energy to their respective work.
…
…
The next morning, Chen Yansen called Tao Jingwen and, with the help of Meng Yuanzhi's connections, obtained a pass to Luzhou University of Science and Technology, allowing him to freely enter and exit the optoelectronic laboratory.
Both mirror polishing and coating processes must be continuously improved through experiments to find the direction of optimization.
No conclusion can be drawn by theoretical calculation alone.
At the same time, Lin Nan also selected a group of R&D personnel who were proficient in ultra-precision polishing technology and sent them to Luzhou.
When Liu Fengjun and others entered the optoelectronic laboratory of Luzhou University of Science and Technology, they happened to see Chen Yansen changing into clean clothes, wearing dust-free latex gloves and a dust-free mask.
Isn’t he the founder of Sunlink Capital?
Why in the lab?
"Mr. Liu, nice to meet you!" Chen Yansen stopped what he was doing, walked straight towards Liu Fengjun, then stretched out his right hand and said.
"Hello, Mr. Chen." Although Liu Fengjun had a lot of questions, he didn't dare to ask directly.
He is a senior researcher in the ultra-precision machining team of the National University of Defense Technology. He has a doctorate degree and is highly intelligent.
With such qualities, he is destined not to say anything that shows low emotional intelligence.
"The lab just finished debugging the ion beam polisher. It's a good opportunity for you to come over. Let's take a look at the parameters together."
Chen Yansen withdrew his right hand and pointed to the operating screen beside him, where a dense stream of data was dancing. He then continued, "I've seen the rough mirror blanks you made in Shanghai. The silicon-based material is pure enough, and the initial surface shape error is still 3 nanometers. It needs to be pre-treated by magnetorheological polishing first."
Liu Fengjun's pupils shrank slightly and his heart was shocked.
He subconsciously walked to the operating screen and his eyes fell on the pretreatment parameters of magnetorheological polishing.
What surprised him was that the screen not only clearly listed the particle size ratio of the grinding fluid at different rotation speeds and the magnetic field intensity gradient curve, but also marked a clear node that "the error after pre-processing must be controlled within 500 picometers."
"Mr. Chen, have you calculated the stress release curve of silicon-based materials in advance?"
Liu Fengjun couldn't help but ask.
You should know that silicon-based mirrors will produce tiny deformations due to stress accumulation during the grinding process. This is the most difficult problem in the field of ultra-precision machining and a technical obstacle that major domestic universities and research institutes have been unable to overcome.
Now, the solution has been found here.
He has been immersed in this field for many years, and because he understands it, he knows how much ingenuity is hidden behind this set of parameters.
Chen Yansen nodded slightly. "Silicon-based materials have a delayed stress release. A 0.3% compensation margin must be left during pretreatment. Otherwise, springback errors will occur during cooling after polishing. Let's get started. Feel free to ask me if you have any questions."
"Xiao Wang, adjust the magnetorheological polishing machine according to these parameters and measure the stress distribution of the first rough piece first."
Liu Fengjun turned around and gave instructions to the researcher behind him, his voice filled with unconcealable urgency.
Chen Yansen said nothing more and turned to walk towards another device.
In the following days, Liu Fengjun followed Chen Yansen around, acting like a student, assistant and follower.
The more he learned, the more he realized Chen Yansen's amazing talent in ultra-precision machining.
Once upon a time, Liu Fengjun was also the top scorer in the college entrance examination and was admitted to the junior class of the National University of Defense Technology. He was considered a scientific research genius among his peers, but in front of Chen Yansen, he was like an ant looking at the sky.
Chen Yansen only spends two hours at Luzhou University of Science and Technology every day, and most of the work is done by Liu Fengjun and others.
They first developed sub-aperture stitching technology, then introduced computational holography technology, and by equipping atomic force microscopes and optical scatterometers, they were the first to improve the detection accuracy to the picometer level.
As soon as the news came out, everyone in the R&D center of the Shanghai Optical Department was instantly cheered up.
After all, with testing tools, process improvements have the right direction to follow.
The other side.
Tsinghua University, Huazhong University of Science and Technology Instrument Development Center and Northern Microelectronics Technology immediately began the research and development of target materials and coating equipment after obtaining the latest version of magnetron sputtering technology.
However, the first difficulty lies in the purity of the molybdenum silicon material and the uniformity of its microstructure.
After learning about this, Chen Yansen combined vacuum hot pressing sintering and plasma densification technology, and immediately broke through the bottlenecks in target material purity and structure.
Once the bottleneck is broken, subsequent research and development will be like opening up the Ren and Du meridians.
The research and development of lighting systems has made great progress!
(End of this chapter)
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