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Chapter 205 Rapid Crystal Pulling

After we get the sand, we need to extract silicon from the sand. Speaking of the element silicon, it is the second most abundant element on our planet. No.1 is the oxygen we are very familiar with,
Oxygen is indispensable for our survival.Oxygen is everywhere, and so is silicon.

It exists in the house in our life, the ground under our feet.Animals, trees and even water contain silicon.

The purity of silicon in nature cannot meet our requirements, and basically exists in the form of compounds.

So the first step we have to do is to purify.

"Start." Zhang Xingchen gave an order.

A steady stream of sand was poured into a huge, intensely hot furnace.

Coke was also poured in with the sand, so that under the action of high temperature, the sand and coke began to react.

This is essentially the reaction between silica and carbon.

Eventually silicon and carbon monoxide gas are formed.

Carbon monoxide gas is extracted, because carbon monoxide is a poisonous gas, and it needs to be processed, transported to oxygen, and reacts with oxygen under the action of high temperature, thus forming carbon dioxide.

We consider carbon dioxide to be a non-toxic and harmless gas that can be emitted into the air.

This is only the first step, and what is produced in this way is with impurities.These impurities are silicon dioxide, silicon monoxide and calcium oxide and so on.

So we call the silicon produced by this method crude silicon.

Further purification is required.

The crude silicon is transported out from another outlet of the intense heat furnace for further purification.

It was transported to another intense furnace for chlorination.

Zhang Xingchen gave the order again: "Rush into the chlorine gas."

Under the effect of high temperature, crude silicon and chlorine have undergone a full chemical reaction.

Chlorine and silicon react to form silicon tetrachloride and silicon trichloride.

After an hour, the reaction between chlorine gas and crude silicon is sufficient, after which the temperature of the intense heat furnace can also be slowly lowered.

Silicon tetrachloride and silicon trichloride will slowly change from gas to liquid as the temperature decreases.

As long as the temperature is high, any substance can be vaporized.

At this time, the objects we get not only contain silicon trichloride and silicon tetrachloride, but of course there will be impurities, including liquid impurities and solid impurities.

Compared with liquid, solid impurities are very easy to extract.

Just filter it.

As for liquid impurities, we can remove sand according to the different densities of different liquids.

We can also use distillation, and we can also use different density methods for purification.

After several purifications, we got higher concentrations of silicon tetrachloride and silicon trichloride.

The next step is to put silicon tetrachloride and silicon trichloride into another strong furnace.

Fill with hydrogen.

This time it was filled with hydrogen.

The strong heat furnace is closed and under the action of high temperature.Hydrogen reacts well with silicon trichloride and silicon tetrachloride.

Under the action of high temperature, silicon tetrachloride and silicon trichloride are reduced, lose oxygen, and form high-purity silicon.

Why must the reaction be carried out at high temperature?
Because any object is under the action of high temperature, the atoms in the microscopic structure will be particularly active.

Simply put, it means thermal expansion and cold contraction. In this case, because there is a heat source, the atoms absorb heat continuously, and it is easier to get rid of the control of the nucleus, and it is easier to carry out chemical reactions.

At this time, silicon can be called high-purity, which is 99.999999999% in numbers, which is called eleven nines.

But such silicon, in fact, still cannot be made into wafers.

Although it has met the requirements in terms of purity, it is still not acceptable in terms of atomic structure.

Because the silicon produced in this way is polycrystalline silicon, if you want to make it into a wafer, it must be monocrystalline silicon.

Under the microstructure, silicon atoms are combined in a specific order to form crystal nuclei one by one, and these crystal nuclei then continue to grow to form crystal grains.

The material composed of crystal grains with different crystal plane orientations is called polysilicon.

As for single crystal silicon, the substance composed of crystal grains with the same crystal plane direction is called single crystal silicon.

Compared with physical and chemical properties, monocrystalline silicon is much superior to polycrystalline silicon.

Therefore, in order to manufacture chips with excellent performance, only single crystal silicon can be used.

What needs to be done here is to turn polycrystalline silicon into monocrystalline silicon.

The equipment that can do this kind of thing is the crystal pulling furnace.

From this point we can see the value of the crystal pulling furnace.

It can be said that turning polycrystalline silicon into monocrystalline silicon is the most difficult and important step.

A steady stream of polysilicon is fed into the crystal pulling furnace.

at this time.The crystal pulling furnace attracted everyone's attention.

When polysilicon enters the crystal pulling furnace, the first thing to do here is to pour argon gas into the crystal pulling furnace.

The purpose of flushing argon is to expel the air inside.

As an inert gas, argon cannot react with polysilicon even under high temperature.

The purpose of rushing into the argon gas is to prevent the extraction of impurities in the air from reacting with polysilicon under high temperature, so as to avoid the formation of impurities.

At this time, the argon gas is filled, not only the air in the sub-chamber of the crystal pulling furnace must be exhausted, but also the small sub-chamber and furnace cylinder of the crystal pulling furnace must be cleaned to avoid residues.

All the air in the space must be squeezed out.

After filling with argon gas.Only then can it be heated slowly.At that time, it must be heated evenly, so that the polycrystals in the crystal pulling furnace are evenly heated.

Under the effect of high temperature, the polycrystals began to melt slowly, and when they melted into liquid, the quartz pot containing the polycrystals began to rotate, driving the entire polycrystals to rotate together.

At the same time, a seed crystal will slowly come down directly above the quartz pot until the seed crystal touches the polycrystalline liquid in the quartz pot.
It's like a superficial touch.

At the moment of contact, the seed crystals start to rotate in the opposite direction to the quartz pot, so that the seed crystals and polycrystals have a relative movement on the horizontal plane.

When the sub-crystal rotates slowly, it will continue to pull up, driving the polycrystalline liquid to go up. As the sub-crystal rises, a cylinder is slowly formed.

In this way, a single crystal rod will be formed, which is a 20-inch single crystal rod.

It's very simple to say, but the whole process is calculated in extremely detailed, there can't be a slight error, otherwise all previous efforts will be wasted, or the generated single crystal rod will end in failure.

Time passed by every minute and every second, and it took nearly three hours to form a single crystal rod.

"It's too fast, it's simply too fast. Compared with this one, the previous crystal pulling furnace is simply a turtle."

"Where did the boss get such a crystal pulling furnace?"

(End of this chapter)