Chapter 379 PMOS
It's not that I don't say it all at once, but every time I say a sentence you interrupt me to make some comment, Linochka thought.

"Kerosene? The calorific value of kerosene is higher than that of alcohol. Ahaha, is this the reason?"

The Minister was relieved.

It's not that he has to find some reason to make himself happy, but these situations seem insignificant individually, but when they are combined together, they are somewhat surprising.

A longer range, a larger warhead, and the same size and weight, this means that the other party must have some technology that we are not aware of.

"Comrade Minister, should we try replacing the alcohol in P-15 with kerosene?"

P-15 is the 544 missile.

"Oh, no! The lower-level Davari will complain. At least the current P-15 cannot be replaced! They are used to maintaining this kind of missile, aren't they?"

I have to say that as a minister, he is very sympathetic to his comrades at the grassroots level.

We, the soldiers of the Zhengmao Banner, love to protect alcohol fuel!

"Comrade Linochka, if there is any new news over there, please tell me as soon as possible. By the way, tell the comrades in Lubyanka that they need to make more efforts!" The minister always felt that something was wrong, but he didn't know what it was.
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Gao Zhendong was unaware of the old Russian's dilemma; he was struggling with his own issues.

In fact, it is not a dilemma, it is just about choosing a suitable path among the complicated processes.

Although MOS technology has been selected, MOS technology also includes PMOS (P-channel MOS), NMOS (N-channel MOS), CMOS (complementary MOS), etc.

Each process of these technologies has different options.

It's like playing with building blocks. If you want to build a park, there are different ways to build it. As the saying goes, everyone has their own way of killing the pig and the butt.

However, Gao Zhendong didn't have much to worry about when it came to the types of MOS. He could just go with PMOS. As the earliest MOS technology, it naturally had its advantages.

Guess why it's the first? Simple!

PMOS only needs five photolithography steps to complete.

P-area lithography, gate lithography, contact lithography, metal lithography, and pad lithography, with different deposition or oxidation processes added between each lithography.

The P region, gate, external contact holes, internal wiring of the chip and lead-out solder joints used for packaging are formed respectively.

Moreover, the mask needs to be strictly aligned and overlaid only in the second grating lithography, and the alignment requirements at other times are not so high. This makes Gao Zhendong, who has limited technical conditions and is stretched to the limit, feel very comfortable.

Putting aside packaging, it only takes 12 steps to go from a silicon wafer to a semi-finished product filled with finished chip cores (DIE), and that includes the step of preparing the silicon wafer.

Even if you don’t want the passivation step, the first four photolithography steps are enough, and the corresponding process is reduced to 4 steps.

This is really simple and does not require much in terms of materials.

There are only three elements to consider introducing.

- Oxygen to form the oxide protection layer, boron to form the gate, and aluminum to form the metal wire.

Aluminum does not need to consider the issue of doping and diffusion, it is only used for deposition.

A retired old man: It’s so much fun.jpg.

The difficulty of NMOS and CMOS is much greater than that of PMOS. Apart from other things, PMOS can at least be used to make logic integrated circuits. Moreover, the 10μm process can be used to make C8008, and in fact, there is no problem with using higher processes.

After selecting PMOS, Gao Zhendong quickly determined the process route.

Don't do the passivation in the last step, and do 4 photolithography steps only until the metal photolithography is completed.

As for why he chose this, of course it’s because it’s simple, and he started out with a relatively rough process, so this level is enough.

Moreover, by eliminating this step, costs will also be reduced.

First, we need to develop the logic gate circuit to support the production of DJS-60D, and then we can develop better ones.

First solve whether it exists, then solve whether it is good or not.

After selecting these, Gao Zhendong started copying the book quickly. He spent an entire afternoon quickly copying the book. The next day he called Factory 1274, which was already a little impatient.

More than an hour later, Director Lu and Chief Engineer Lu arrived with their people. They had been waiting for this day.

Looking at the process design guidance documents provided by Gao Zhendong, the two were a little confused. How come this thing has become thinner than the original one?

Everyone thinks that advanced technology must be complex, and once it is complex, the data will be very thick.

"Chief Engineer Gao, this process is done part by part at a time. Is this what we need to do in the early stages?" asked Chief Engineer Lu.

Gao Zhendong was confused. When did I say I would do it piece by piece? "No, this is all of it."

"All?" The two were shocked. How could this be possible? Gao Zhendong smiled and explained the simple outline of the process to them. The two fell into a state of "I don't understand, but I am shocked."

Gao Zhendong had to explain: "Although PMOS technology is newer, it is simpler in terms of process and best suits our current situation."

Chief Engineer Lu was overjoyed. He had shaved off half of his hair because of the complicated process of bipolar transistor semiconductors. He felt that this was the first good news he had heard today and also the best news. Chief Engineer Gao was really talented.

"Chief Engineer Gao, are you saying that this technology can accomplish what bipolar semiconductors require more than a hundred steps of process with just a few photolithography steps and dozens of processes?"

Gao Zhendong smiled and said: "The development of technology is actually like this. Advanced does not mean complicated. Some advanced technologies can be so simple that we can hardly imagine."

It even looks super unsophisticated, Gao Zhendong thought.

They both still believed in Gao Zhendong, and what he said had basically never come to pass.

"Chief Engineer Gao, this is great, what do we need to do?"

Gao Zhendong said: "I see that the factory has a diffusion furnace now, right?"

Director Lu nodded: "Yes, this is one of our basic production equipment, there are a lot of them."

"What is the highest temperature control accuracy? Can it reach plus or minus 1 degree Celsius?" Gao Zhendong asked. This accuracy involves the diffusion doping effect.

Chief Engineer Lu knew: "This cannot be achieved. There is a gap. It is mainly due to the sensor problem."

The K-type thermocouples they use now have no problem with the temperature measurement range, but the accuracy is quite poor, 2.5 degrees Celsius or 7.5 thousandths, which is far from the accuracy requirement.

Gao Zhendong thought about it and did not recommend Type B thermocouple. The error of Type B is 2.5 thousandths, which is not enough and its response speed is slow.

"Let's add a platinum resistor for indirect measurement as an auxiliary sensor, combined with a K-type thermocouple and a DJS-60D running the PID control algorithm. It should be controllable."

The response speed of platinum resistors is also slow, but this can be solved to some extent by means of algorithms. The accuracy of platinum resistors far exceeds the requirements, and the best can reach 3/1000 degrees Celsius.

The biggest problem with platinum resistance is the temperature measurement range. Semiconductor production requires a temperature range of more than 1000 degrees Celsius, which exceeds the temperature measurement range of platinum resistance. However, if the indirect measurement is well designed, there will be no major problem.

Therefore, Gao Zhendong came up with the method of indirect measurement using platinum resistance + direct measurement using K-type thermocouple. One measures accurately, and the other measures quickly. Together, they are invincible.

He didn't know how diffusion furnaces would solve this problem in the future, but this was how he solved it.

The reason why this diffusion furnace is so important is that many processes depend on it.

Oxidation, deposition, diffusion, diffusion-oxidation, all of these depend on this thing.

There is another diffusion-oxidation process, but Gao Zhendong did not choose it because choosing that process would add an additional equipment called epitaxial reaction system, which would be troublesome.

Therefore, Gao Zhendong chose the "thermal oxidation method" which can be completed by a diffusion furnace.

Gao Zhendong thought about it and gave another support: "When the time comes, I will support some of your technicians who specialize in computer control and thermocouple applications to cooperate with you in this matter."

Chief Engineer Lu and his colleagues were relieved now. With Chief Engineer Gao's elite troops personally supporting them, things would be much easier.

Gao Zhendong was also very happy. The three core equipment in the PMOS technology chip manufacturing stage, a photolithography machine and a diffusion furnace, were already available, and only one was left.

"Director Lu, what is the current situation of the vacuum evaporation equipment?" This thing was not found in the current status of Factory 1274, so the situation may not be optimistic.

Director Lu shook his head: "No, we didn't have any use for this before."

Vacuum evaporation is a device that evaporates metal under vacuum conditions to form a metal coating on the surface of the workpiece. In the chip manufacturing industry, its upgraded version is the sputtering equipment.

However, sputtering equipment is used for metals such as tantalum and niobium, which have good sputtering properties. However, the aluminum used in large quantities in the wiring within the chip is different and is always evaporated.

However, there are several types of evaporation, including resistance heating, which directly uses metal resistance materials such as tungsten to heat high-purity aluminum to form metal vapor and complete the evaporation.

Another method is electron beam evaporation, which can avoid some disadvantages of resistance heating, such as the heating resistors coming into contact with the oxidizing atmosphere in the process, which will evaporate themselves, and they will even react with the evaporated metal, which will make it even more difficult to heat.

Gao Zhendong thought for a while and said: "Then let's make a resistor vapor deposition machine."

Electron beam evaporation relies on the magnetic field to accurately deflect the electron beam and hit the target material for heating. Not to mention the source of the high-energy electron beam, the source of the magnetic field is also a problem. There is no need to think about permanent magnets, and the electromagnetic field is also a problem under current conditions.

On the contrary, the technologically backward resistance heating is more feasible now. There is always a reason for the existence of every technology.

Anyway, this is not a very demanding process at the moment, so although the entire integrated circuit process seems to be full of makeshift and compromise to Gao Zhendong, it is almost the most appropriate at this stage.

However, the two people from Factory 1274 obviously do not think that this process is just a makeshift one.

　One more chapter

　　
　
(End of this chapter)