Technological power starts with upgrading lenses

Photolithography is the most critical link in the chip manufacturing process. Its basic principle is actually very simple, which is to use light to complete the engraving of silicon wafers.

The silicon wafer in lithography is like a projection cloth hanging on the wall, and the lithography machine is a projector.

If the surface of the projection cloth is uneven and has undulations, the projected image will naturally be distorted.

In photolithography, surface defects on the silicon wafer will cause the projected circuit design path to deform, leading to a reduction in yield or even the scrapping of the entire wafer.

Therefore, if you want to obtain a silicon wafer that can be used to manufacture chips, you need to polish and polish the cut single crystal silicon wafer until its surface flatness is less than 1.5nm RMS.

This is equivalent to hanging a large curtain in a movie theater. Its surface undulations cannot exceed the size of a hair, which is infinitely close to a perfect mirror.

Therefore, the requirements for the silicon wafer manufacturing and polishing process are naturally extremely important.

From the small steel ball on the tip of the ballpoint pen, to the silicon wafer that is the raw material of the chip, to the lens on the photolithography machine, and finally even the flawless water droplet in the science fiction novel The Three-Body Problem...

In fact, the test of the level of a civilized industry is to see how finely you can make an item.

To make fine things, you naturally need a clean room with clean air. Otherwise, the air will be full of dust and bacteria, and you will not be able to make qualified silicon wafers no matter how much you polish them.

"In fact, in recent years, we have been able to achieve a flatness of 2.6nm RMS by imitating equipment from island countries. But no matter how much we check, even if every part has reached the standard, we still can't continue to make breakthroughs..."

Yan Hui wore protective clothing while introducing their research progress to Kang Chi.

"What kind of polishing fluid is used to polish to 2.6nm RMS?"

"Based on SiO2, add 0-70wt% hydrogen peroxide, and finally use KOH to adjust the pH to 8.5."

Kang Chi nodded: "Let's take a look first and then talk."

After the two people put on protective clothing, they quickly came to the polishing laboratory, and then Yan Hui hosted a polishing experiment demonstration to Kang Chi.

In traditional silicon wafer polishing, a mechanical polishing machine is usually used to initially polish the silicon wafer, then clean it, and finally perform chemical mechanical polishing, also known as fine grinding.

Precision grinding is a method that utilizes the chemical corrosion function of the polishing liquid and the mechanical polishing of the mechanical turntable. The two work together to achieve the process standards of the silicon wafer.

The result of the experiment was 3.1nm RMS, which was much worse than the limit of what they could do.

Kang Chi thought for a moment and then said: "Change to 30wt% Al2O3 base fluid, add 65wt% potassium permanganate as a chemical polishing fluid, and use 5wt% HNO3 to adjust the pH value to 8.0 and try again."

Yan Hui nodded, led the researchers to prepare the polishing fluid, and then conducted the experiment again.

"Flatness 5.9nm RMS."

Seeing this result, Yan Hui, who had a little expectation, couldn't help but show a look of disappointment.

But Kangchi remained unmoved and reported another set of polishing fluid ratios, asking them to conduct the third experiment again.

"Flatness 5.9nm RMS."

5.9?

Or 5.9? !

Is it a coincidence?

Although 5.9 was obviously far from the standard, Yan Hui seemed to realize something and turned to look at Kang Chi in surprise.

"You... calculated it?"

"So be it."

Kang Chi nodded.

Yan Hui was completely stunned now.

You must know that the technical difficulties of chemical mechanical polishing are that in addition to the hardware of the polishing equipment meeting the standards, the chemical polishing liquid must also be prepared according to the equipment performance and silicon wafer parameters to achieve the perfect combination of chemical polishing and mechanical polishing.

If you want to debug it well, you first need to know the equipment well, and secondly, you need to have rich experience in mixing polishing fluid.

But just through one experimental demonstration, Kangchi was able to report two sets of polishing fluids with different compositions seemingly easily, and in subsequent experiments, the flatness reached the same value...

Isn't this a bit unbelievable?

Even Yan Hui, who has participated in countless tests, would never be able to achieve such precise control without computer simulation.

The estimated error must be at least 0.3nm RMS.

He asked in disbelief: "How on earth did you do it?"

"Well, I can't tell... maybe it's some kind of intuition. I'm quite sensitive to mechanical things."

Kang Chi thought for a moment and then continued,

"I estimate that the normal level that this polishing machine can perform stably should be around 3.0nm RMS. 2.6nm RMS was only achieved by accident because of accidental factors. It will definitely not exceed three times."

Yan Hui was stunned again, apparently Kang Chi had guessed it.

"Indeed, only once..."

Kang Chi originally wanted to say something, but his stomach was already growling with hunger.

Looking at the time, I found that after three rounds of experiments, it had already reached eight o'clock in the evening without even realizing it.

"I'm sorry, I didn't notice it's so late... Everyone hurry up and pack up and go eat first. Thank you for your hard work today."

"Yes." Yan Hui nodded and said, "After everyone has finished eating, we will come back at nine o'clock to continue."

"Come back and continue?" Kang Chi couldn't help showing a strange expression, "Why continue?"

"Let's do an experiment."

"It's useless. This is not a matter of the proportion of polishing liquid at all. You are doing useless work." Kang Chi shook his head directly and said, "After dinner, go home early to wash up and go to bed. We will come over tomorrow to dismantle the polishing machine. If I guess correctly, there is a problem with your equipment installation."

Hearing that Kang Chi had guessed the problem, Yan Hui suddenly became excited: "You don't have to wait for tomorrow, we can take it out and dismantle it for you now!"

Kang Chi rolled his eyes at Yan Hui: "I'm hungry and tired."

"..."

Yan Hui couldn't help but feel embarrassed.

"Ahem...Sorry, I forgot that you just came from Steel City today."

"Even if you haven't rushed from the Steel City, it's time to eat and rest at this point, and so do you. Don't work overtime in the future if you can. Although time is tight, we must also pay attention to efficiency in our work instead of just piling up time. You all If you feel dizzy, why do you do research?"

"..."

By the time I finished cleaning up the laboratory, took off my protective clothing and came to the company cafeteria, it was already nine o'clock in the evening.

Because the silicon wafer production department works 24 hours a day, and the scientific research dogs in the R\u0026D and manufacturing center often work overtime all night, the company's canteen is also available 24 hours a day, so you can eat at any time.

The aunt who was serving food in the cafeteria was very enthusiastic when she saw Yan Hui and put more dishes on his rice plate.

Kang Chi couldn't help but look at the aunt one more time.

Um……

Although he is a little older, he can still be considered charming.

"Ahem, don't think too much." Yan Hui saw Kang Chi's complicated expression and coughed quickly, "If she knew you were the big boss, she would probably beat her even more..."

"I didn't say anything, why are you nervous?"

Yan Hui: "..."

…

After eating, Kang Chi contacted the company's administrative director by phone, and then under his leadership, he and Chen Hai went to the house that the company had prepared for him in advance.

This is a two-story villa with five bedrooms and two living rooms, which is quite unique.

Living alone, it seemed a bit empty and deserted.

Um,

After Chen Hai sent Kang Chi home, he didn't know where he went. Is it probably in the building next door?

Kang Chi didn't invite him to live with him either.

Otherwise, if two grown men live under the same roof,

How dignified! ?