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Chapter 214 Proximity Exposure

We can fully imagine how big 30 square kilometers is.

The area of ​​the island country is only 37 square kilometers.

It is as big as an island country. Our country is about 960 million square kilometers, which is equivalent to 3% of our land area.

This area is not small, but the error of such a large area is only one meter, what a terrifying thing this is.

This is just a DUV lithography machine with such precision, what if it is replaced with a more advanced EUV lithography machine.

That precision is higher!

Still taking 30 square kilometers to calculate, the error will not exceed ten centimeters.

"Ten centimeters..." Zhang Xingchen's eyes were shining strangely, and Xiaobai didn't know what Zhang Xingchen was thinking.

So far, only the Skoll company of the German tank can do this on our planet.

Even the ASML company in Windmill Country purchased lenses polished by this company.

"The lithography machine we manufactured this time has a total of three platforms, which are used to hold masks, silicon wafers and finished products."

The purpose of placing the finished product is actually to test the chip and check whether the chip meets the requirements.

Compared with the last platform, the first two platforms are undoubtedly much more important.

There are two ways of movement of these two platforms, the first one is relatively static.

The lithography machine in relatively static mode can make the circuit diagram of the chip engraved with light at once, and the speed is relatively faster, but this is equivalent to direct rubbing.

This causes the light to scatter easily, which greatly affects the yield.

The second mode is that the light moves along with the platform where the eye mask is placed. In this way, the light is concentrated, the engraved circuit diagram is clear, the error is small, and the natural yield will increase.

"However, the requirements for mechanical precision are very high. The DUV lithography machine we manufactured can already control the error within ten nanometers. It is enough for the manufacture of 45-nanometer chips, and it can already meet the requirements. No It is necessary to use the second mode."

"If you use an EUV lithography machine, then the requirements for the error will be more stringent, and it must be kept within two nanometers."

In addition, there is one point to be explained here. The acceleration of the initial velocity of the two workbenches is very fast when they are moving, even comparable to the acceleration when firing a cannon.

Moreover, when manufacturing chips, the lithography machine must be in a constant temperature state, and the temperature requirements are very strict. In the working state, the temperature error cannot exceed one thousandth.

"We made this DUV lithography machine. The two planes are stationary so that it is easier to manufacture, and it can also meet the requirements."

There are also three relative positions between the mask and the silicon wafer. The first is that they are in contact with each other; the second is that the two of them are very close to each other, but they are not in contact; projection.

That is contact exposure.Proximity exposure and projection exposure.

The best effect is projection exposure, and the worst is contact exposure.

"We choose the intermediate proximity exposure, because it is not necessary to use the best DUV lithography machine, which greatly increases the difficulty and cost, as well as the abundance of functions."

Contact exposure is actually very complicated, but it can be divided into three types in general, one is vacuum contact, one is hard contact, and the other is soft contact.

Although the names are different, the latter two words are unmistakable, they are all contacts.

Because the mask and the silicon wafer are in contact with each other, they will definitely rub against each other, which will not only affect the photoresist on the silicon wafer, but also affect the precision of the mask and the surface of the mask. circuit diagram.

Because of the mask, it needs to be reused, but every time it is used, it will be in contact with the silicon wafer, so the template will damage the circuit on it over time.The circuit diagram will become more and more blurred, and even defects will appear, which will greatly increase the breakage rate of the mask.

After a period of use, the mask becomes unusable.

In this way, contact exposure has a serious disadvantage, which has led to the gradual elimination of contact exposure.

It is a pity to say that the lithography machines produced in our country are basically contact exposure, because the technology and manufacture of contact exposure are relatively simple, and it is relatively easy to manufacture.

But in foreign countries, the light is basically eliminated during contact.

As for projection exposure, it is generally only available on more advanced EUV lithography machines.

For advanced DUV lithography machines, there is no need to use projection exposure. We are only using proximity exposure. The distance between the silicon wafer and the mask plate is very small, and this distance is kept below 260um. We can't see it with our naked eyes, and we must use a high-powered magnifying glass to see it.

Projection exposure is very complicated, but it is basically divided into three types: scanning step projection exposure.Not only repeated projection exposures.Scan projection exposure.

Undoubtedly, these three methods all require very, very high requirements for technology and manufacturing capabilities, almost to the point of abnormality.

"Even if I want to manufacture an EUV lithography machine, it will take a long time, let alone others."

The advanced lithography machines produced by ASML use projection exposure, and their output is not high, and 30 EUV lithography machines can be produced a year.

It can be said that it is not easy to manufacture a lithography machine. We can even say that a lithography machine is the most sophisticated equipment in the world, at least at this stage, a lithography machine is the most sophisticated instrument.

The manufacturing of lithography machines can largely reflect the stage of a country's industrial level.

A lithography machine has more than 10 parts, 3000 lines, 4 bolts, and a hose length of more than two kilometers. In addition, there are more than 190 sensors, including 16 subsystems.

So many zero supplementary angles are combined to form a lithography machine.All parts on the equipment cooperate with each other, and there cannot be a single problem.

If there is a problem with a small part, it can cause the entire machine to fail to operate normally, and even a small bolt cannot have a problem.

It is no exaggeration to say that one hair can move the whole body.

Don't underestimate a bolt, it may affect the operation of the whole machine. It can be said that as long as the parts installed on the lithography machine are important parts.

"By the way, ASML can produce close to 1 lithography machines a year. If we drive the horsepower, how many lithography machines can we produce in a year?" Zhang Xingchen asked.

Zhang Xingchen was still very curious about this question.

(End of this chapter)