Chapter 370 MOS
In the college entrance examination in 60, there was no such thing as checking scores. All you had to do was take the exam and wait for the results. Admission letters would probably be sent out in August.

Moreover, given Lou Xiao'e's situation, she would definitely not be admitted in the first batch this year, so the time would have to be postponed a little further. The characteristic of this batch is that "can be admitted to confidential majors."

So Lou Xiao'e and Gao Zhendong were not in a hurry. They just did what they were supposed to do. Gao Zhendong went to work while Lou Xiao'e took care of the housework.
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In the office, Gao Zhendong was thinking about the matters of Factory 1274.

Due to technological development reasons, MOS (metal-oxide-semiconductor) technology was not fully formed at this time.

The integrated circuit technology of Factory 1274 still follows the path of bipolar semiconductors with PN junction isolation proposed in 58. This is also the limit of Factory 1274's own capabilities, and it has even exceeded the limit.

This put Gao Zhendong in a dilemma: should he continue to let Factory 1274 use bipolar semiconductors, or should he just go straight to MOS technology?
The two are not completely substitutable. In fact, bipolar semiconductors have obvious advantages over MOS semiconductors in many areas.

For example, transistors switch faster, can reach higher frequencies, have lower design phase costs, and have higher precision internal components.

For Gao Zhendong, what he wants is semiconductor technology that can play a greater role and have greater potential in the direction of computer technology.

Therefore, even though integrated circuits have other routes at this stage, such as ultra-small assembly and membrane integrated circuits, Gao Zhendong did not consider these routes. These routes have their special uses and are not without prospects, but in the direction of computers, they have no future in the foreseeable future.

The only question is, at this stage, should we use bipolar? Or should we take a big step and consider MOS directly?

At this stage, bipolar has its advantages in integrated logic gate circuits.

After much deliberation, Gao Zhendong decided to take a big step and go for MOS.

The bipolar type is faster, but at this time it can't be much faster, and it is useless without the support of other technologies. For computers, the speed of tens of MHz that the early MOS can achieve is completely sufficient.

The 80 in the 80286s was only 20MHz. In the 60s, the faster switching speed of the bipolar type was of no significance to Gao Zhendong's needs.

Although the internal components of bipolar type are more accurate, as a digital circuit, as long as it can complete the expected state transfer under the specified conditions, the high accuracy of the components is of no use. This is not an analog circuit and the requirements are very different.

Besides, the high precision of bipolar components is only relative to MOS. The actual gap is not even as good as the pot calling the kettle black.

To say that the cost is low during the integrated circuit design stage is a false proposition at this stage, as labor costs are not taken into account at this time.

Another problem with MOS is that once a chip is finalized, it is difficult and costly to modify.

But for what Gao Zhendong wants to do, this is not a problem at all.

As chips used on a large scale, whether they are logic gate integrated circuits, CPUs, or DRAMs, they are finalized and will not be modified at will. They will be mass-produced, so this is not a problem at all in this regard.

The most important point is that Gao Zhendong knew clearly that there was no such thing as bipolar since the beginning of CPU and semiconductor memory. Bipolar was good for integrated logic gate circuits, but it was completely useless for CPU and semiconductor memory.

In other words, in this regard, bipolar semiconductors have never been favored from a technical and economic perspective.

Intel 4004, 10μm PMOS.

8008, 10μm PMOS.

The first 4Kbit DRAM, 8μm NMOS.

The first 16Kbit DRAM, 5μm NMOS.

The famous 8086/8088, 3μm NMOS.

The 80286, 1.5μm CMOS, completely consolidated Intel's decades-long foundation.

As for why everyone unanimously chose MOS technology for this application, we have to talk about the advantages of MOS.

This thing is simple to make! Much simpler than the bipolar type, not even a little bit!
Leaving aside the complex technical principles and so on, to summarize briefly, taking PMOS and double diffused epitaxial bipolar as examples, to achieve almost the same effect, the process differences between the two are huge.

The number of PMOS epitaxy is 1, the number of process steps is up to 45, the high-temperature process is 2 steps, and the photolithography is up to 5 times.

While these numbers for double diffused epitaxial bipolar type are more than 4 times, 130 steps, 10 steps, and 8 times.

Fewer processes, simpler technology, and higher yield rate
For mass production, this is all money!

And for Gao Zhendong now, the fewer process steps, the higher the success rate.

The basic technologies used by the two are actually similar. The biggest difference lies in the working principle of the transistor. Therefore, in terms of technical difficulty at this stage, with Gao Zhendong as the knowledge porter, the later and more advanced MOS is even lower than the bipolar type.

There is also a very counterintuitive and unnatural aspect to MOS technology.

Within the same generation, changing the design of the MOS circuit has no effect on the MOS process. The performance change of the MOS circuit is achieved by changing the geometric design of the MOS field-effect transistor.

In this case, the bipolar type needs to change the process parameters such as diffusion source, diffusion time, diffusion temperature, etc. to achieve the change of circuit performance, but the MOS circuit does not change, and its process remains unchanged. Moreover, this characteristic of changing the geometric design to change the performance brings another benefit of MOS integrated circuits - it is easier to implement computer-aided design, and realize semi-automatic or automatic design.

In addition to the above advantages, bipolar semiconductors themselves have a major flaw that means they will not go far in large-scale and ultra-large-scale integrated circuits.

——It can’t be made small! But MOS can!

There are many reasons for this situation.

Firstly, the area of ​​MOS tubes is naturally smaller than that of bipolar tubes.

Secondly, bipolar transistors require isolation PN junctions or isolation wells, but MOS does not.

Third, MOS inherently provides two layers of interconnection, which makes its internal wiring more convenient.

These many advantages of MOS have brought about some derivative benefits at the system level, such as higher system performance, better design predictability, better reliability and maintainability, etc.

Interestingly, the concept of MOS field-effect transistors was actually proposed earlier than bipolar transistors, but the reason why they became popular later was due to technological constraints.

It's like cars. The concept of electric cars predates steam cars and internal combustion cars, which was in the late 19th century. However, they were not put into practical use on a large scale until the 21st century.

But the issue of craftsmanship is not a big problem for Gao Zhendong, he can just copy it!
After much deliberation, Gao Zhendong made up his mind: take a big step and do MOS!

As for the bipolar type, leave it to the comrades from other factories and institutes to work on it. I will directly lead Factory 1274 to take off!
For the future development of domestic computer technology, he is willing to take the responsibility and risk. He has already done what he wants. It would be meaningless if he is still timid when he should take a chance and take responsibility for the huge interests of the country and society.

For the period of the early 60s, if Gao Zhendong didn't wear it, no one would be doing MOS. If Gao Zhendong wore it, still no one would be doing MOS. So Gao Zhendong wore it in vain.

Gao Zhendong made up his mind and started to implement this matter.

He called Factory 1274 and told them that he had determined the direction of the integrated circuit process research and adjustment, and then began to compile the process design guidance documents for MOS technology based on the contents of the book Integrated Circuit Engineering Technology.

The design guidance document instructs Factory 1274 on how to design the various processes of MOS technology, rather than directly writing out the processes. It is impossible to write them out, and this is not Gao Zhendong's responsibility.

For Factory 1274, with this process design guidance document, they can carry out targeted and specific process design based on their own conditions, which is more operational and targeted.

This is equivalent to Gao Zhendong telling Factory 1274 what they should do to implement the MOS process, what are the key points of these things, what are the precautions, and how to calculate some important parameters in the middle.

As for each specific step, Factory 1274 carried it out according to this guidance document.

The reason why I write this first is mainly for the sake of the comrades in Factory 1274. The transition from bipolar transistors to MOS, although the technologies used are actually similar, from the surface, this is a radical change.

This kind of shift could easily cause fear among the comrades at Factory 1274 who were not familiar with the MOS process.

So Gao Zhendong simply came up with the design guidance document for the MOS process first. Well, you see, these two things have different names and principles, but when it comes to the technology used in each step, they are actually similar.

It’s very simple, just go ahead and give it a try, there will be no problem.

This will help comrades 1274 get into the state faster. After all, there is a huge difference in perception for them between suddenly being exposed to a new technology that they know nothing about and having to start using it, and directly getting all the key points of this new technology and then deepening their understanding.

1274 On this side, after receiving Gao Zhendong's call, Director Lu and Chief Engineer Lu put aside the last bit of worry in their hearts and put all their energy into the production of triodes.

Since Chief Engineer Gao is in charge of adjusting the integrated circuit process, there is no need to worry about it. Just focus on completing your own work first.

Although the country has begun to switch to the use of DJS-60D, the production task of transistors is still heavy for Factory 1274.

The domestic market is switching to 60D, but the export market is still using 59. Just for this reason, Factory 1274 is destined to reach its full capacity and produce as much as it can.

Not to mention the domestic public’s demand for electronic products.

Not to mention the bias, a radio requires 4 to 9 transistors. After deducting the number required for DJS-59, it is simply not enough.

All in all, everything is fine.

　Three chapters completed today.

　　When I received the review notification today, it said it was one project, but when I got there, I found out that it was one thing with 8 different projects.
　　Time is completely stretched, and the extra chapter I promised yesterday can only be added tomorrow.

　　Due to today's work, I will post two chapters tomorrow afternoon and two chapters in the evening, so you don't have to wait in the morning.

　　
　
(End of this chapter)