Siheyuan: Starting from a fitter

Chapter 118 Successful crystal pulling
I told Zhao Ting the good news in the evening. Although she didn't know these technologies, she was excited for Li Guocheng when she saw him so happy.

After a good night's sleep, Li Guocheng came to the laboratory feeling refreshed and refreshed the next day.

Li Guocheng moved a stool to the door of the assembly laboratory, "Zhou Xiaojuan, please go and inform everyone that I will start the simulation manufacturing of monocrystalline silicon today, please don't disturb me."

Zhou Xiaojuan is very interested in semiconductors. At this stage, Huaxia is actively engaged in semiconductors, bringing semiconductor technology directly to the floor.

Newspapers advertised at length: An old lady on the street could make semiconductors by running a diffusion furnace in an alley.This kind of advocacy that violates basic laws has seriously impacted the semiconductor production R&D process and capital investment in regular factories.

After Zhou Xiaojuan informed everyone, she ran back with curiosity.

Li Guocheng pointed to the stool at the door and said, "Go and guard it for me. This notebook is some summary of my circuit board design. You can read it first. If you are interested, I will leave this task to you in the future."

"Director, Brother Li, please excuse me. Please let me take a look. I promise not to affect your work. I will lock the laboratory door later." Zhou Xiaojuan clasped her hands together, bowed repeatedly, and begged to stay.

"The observation window is only that big. You can see if you want, but don't make a sound." Li Guocheng thought that they would need to study hard in the future, and it might be more beneficial to look at the preparation of single crystal silicon.

After receiving the consent, Zhou Xiaojuan quickly ran to the door, plugged in the bolt, and then ran back happily.

"It's pointless to vacuum now. Please read your notes for a while. I'll call you when the monocrystalline silicon is pulled." Li Guocheng didn't want to waste time.

Now Zhou Xiaojuan agreed to everything, moved a stool and sat next to the vacuum furnace, opened her notes and started reading.

Half an hour later, the vacuum reached the negative third power, and Li Guocheng turned on the crucible heating switch.At this time, the crucible is slowly rotated counterclockwise under the heating of the graphite rod to ensure more uniform heating.

The heating rod has been repeatedly determined, and the set current just ensures that the internal temperature of the crucible reaches 1414 degrees Celsius, which is the melting temperature of silicon powder.

After observing that the high-purity silicon powder in the crucible was completely melted, he said, "Xiao Zhou, I'm going to start." After calling Zhou Xiaojuan, Li Guocheng put on heat-insulating gloves, lifted the handle, and the tip of the pull rod in the vacuum furnace came down toward the silicon solution. .

Because the seed crystals are so precious, in addition to getting one from collecting rags, Wu Liankui later helped purchase 2, for a total of only 3, so they cannot be wasted casually.The tip of the pulling rod is holding a silicon block polished to the same size as the silicon seed crystal. It is used to replace the silicon seed crystal for a simulated crystal pulling test.

The seed crystal acts like a seed. At the interface between the molten polysilicon liquid and the seed crystal solid-liquid, the silicon atoms will follow the silicon atom arrangement of the seed crystal to form regular crystals.

Li Guocheng used the single crystal silicon pulling method introduced in the book. The process is divided into: seeding, necking, shoulder release, equal necking and finishing.

The seed crystal is relatively simple, that is, the seed crystal is immersed in silicon liquid; when pulling the crystal, a thin neck with a diameter of 3 to 5 mm is first introduced to eliminate crystallization dislocations. This step is called necking; then the diameter of the single crystal is enlarged to the process requirements. One step is called shoulder release; with the pulling up, a uniform crystal rod is formed, this step is called equal necking; until most of the silicon melt has crystallized into a single crystal rod, leaving only a small amount of remaining material, the pulling is accelerated to form a pointed cone-shaped bottom This step is called finishing.

Li Guocheng concentrated all his energy on the silicone liquid. He didn't even care about the itching coming from his temples. He gently pressed the lifting lever with his right hand and successfully completed the necking. Unfortunately, he didn't grasp the strength well and broke it directly. This time, he pulled the crystal. fail.

At this time, Li Guocheng noticed that because the observation window was too small, Zhou Xiaojuan's face was almost touching his, which scared Li Guocheng and quietly moved away.

Li Guocheng pressed the lifting rod all the way down, then turned off the heating switch and vacuum switch.

"Ah, why did you stop?" Zhou Xiaojuan realized later.

"If it fails, the silicon block needs to be replaced again," Li Guocheng explained.

At this time, Zhou Xiaojuan's face suddenly turned rosy, and she was tangled in her heart, "Is it possible that I have influenced him?"

Li Guocheng didn't pay attention, "The lifting is too fast and needs more practice."

After the vacuum chamber returned to normal pressure, Li Guocheng opened the vacuum furnace door and replaced the silicon block while wearing heat-insulating gloves.Repeat again, the processes of vacuuming, melting silicon powder, seeding crystals, and pulling crystals.

The failure was different every time. With Li Guocheng's strong control, he could not pull out a polycrystalline rod that satisfied him within a week.

Finally, use your mind to observe the entire process, and note down the temperature changes and lifting speed of each process, especially focusing on the temperature changes during isoneck.

Another week passed. I took the data that Zhou Xiaojuan helped record and analyzed it from the first time. I made a trend chart of the temperature and the crystal pulling stage, and found that most of the failures were related to sudden changes in temperature.

There is only one reason for sudden temperature changes, and that is voltage instability.For verification, several more sets of data were made, and the results were completely in line with expectations.

Now that the cause is found, it is easy to solve.If making an AC voltage regulator, the cost would be too high and the time would take too long. Li Guocheng no longer wanted to wait.

Li Guocheng, who was already confused, had no good solution for the time being, so he had to ask Wang Gong for help.Unexpectedly, when he told the problem, Gong Wang laughed loudly, "With so many devices working together during the day, it consumes too much power and it is normal for the voltage to be unstable. You can choose night."

One word awakened the dreamer. Since Li Guocheng and Wu Liankui explained the reason, since he couldn't do it in the morning, he ignored the follow-up, and gave him and Zhou Xiaojuan a vacation in the afternoon, and went home to rest and adjust their state.

At this stage, Zhao Ting only worked overtime occasionally, and in most cases she commuted to and from get off work on time. Their lives were a mixed bag.

Li Guocheng took a nap in the afternoon and was woken up by Zhao Ting during dinner in the evening.He briefly explained today's plans and reasons to Zhao Ting, and Zhao Ting was very supportive.

At 7 o'clock in the evening, the first assembly laboratory.

"Why are you here?" Li Guocheng looked at Zhou Xiaojuan and asked doubtfully.

"I want to witness the moment when the first crystal pull is successful," Zhou Xiaojuan said confidently.

"Hahaha, this is just a simulation, not a real crystal pulling," Li Guocheng suddenly felt funny, "Go back, it's too late and it's not safe."

Zhou Xiaojuan couldn't find a convincing reason, so she had to leave unwillingly.

Looking at the little girl's leaving figure, Li Guocheng was thoughtful.

Drank a cup of strong tea, washed my hands, and waited until 9 pm.Start the vacuum furnace, evacuate, heat the graphite rod, melt the silicon powder, seed the crystal, neck down, release the shoulder, equalize the neck and finish, all in one go.

Perfect, the polycrystalline silicon rod with a diameter of about 50mm and a length of about 100mm was pulled successfully.There are shallow and even spiral patterns on the surface, but unfortunately the whole body is dark and lacks the luster described in the book.

Next, Li Guocheng repeated it three more times, repeating it perfectly every time.It wasn't until now that Li Guocheng let go of the big stone in his heart.

Seeing that it was already past 3 o'clock in the morning, Li Guocheng simply entered the secret realm to finish his morning class, took a short rest, and at 5 o'clock in the morning, left a note for Wu Liankui and turned around to go home.

At 8 o'clock in the evening, the No. [-] Assembly Laboratory was brightly lit.The onlookers included Li Huaide, Wu Liankui, Wang Gong, Master Yi, Zhou Xiaojuan and Tang Danian.

At this time, Deputy Director Wu Baoguo entered the laboratory and looked at Li Huaide, "Director, all equipment in the entire rolling mill has been shut down."

Li Huaide looked at Li Guocheng and said: "Comrade Li Guocheng, let's get started."

Li Guocheng nodded confidently. The same process, the only difference is that real seed crystals are used.An hour and a half later, a single crystal silicon rod with a diameter of about 50mm and a length of about 100mm was successfully pulled.

Before pulling the crystal, Li Guocheng removed the impurities in the silicon solution through his mind.

After the single crystal rod cooled, what was pulled out was indeed a dark brown single crystal with sharp edges and corners, and the crystal surface was sparkling.This is a complete silicon single crystal rod that Li Guocheng dreamed of day and night.

After receiving Li Guocheng's confirmation, everyone who had dared not show off before gave out huge cheers.Leaning slightly, everyone gathered around the single crystal rod placed on the tray, admiring it.

Li Huaide delivered a passionate speech on the spot and reiterated that he would vigorously support semiconductor research and production.

After the excitement, Li Huaide locked the single crystal rod and the tray in his safe.

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(End of this chapter)