Which processor technological process is better? What you need to know about processors? RAM support
As promised - a detailed story about how processors are made... starting with sand. Everything you wanted to know but were afraid to ask)
I have already talked about “ Where are processors made?" and about what " Production difficulties"are on this path. Today we will talk directly about the production itself – “from start to finish.”
Processor production
When a factory for the production of processors using a new technology is built, it has 4 years to recoup the investment (more than $5 billion) and make a profit. From simple secret calculations it turns out that the factory must produce at least 100 working wafers per hour.Briefly, the process of manufacturing a processor looks like this: a cylindrical single crystal is grown from molten silicon using special equipment. The resulting ingot is cooled and cut into “pancakes,” the surface of which is carefully leveled and polished to a mirror shine. Then, in the “clean rooms” of semiconductor factories, integrated circuits are created on silicon wafers using photolithography and etching. After re-cleaning the wafers, laboratory specialists perform selective testing of the processors under a microscope - if everything is “OK”, then the finished wafers are cut into individual processors, which are later enclosed in housings.
Chemistry lessons
Let's look at the whole process in more detail. The silicon content in the earth's crust is about 25-30% by weight, making this element second in abundance after oxygen. Sand, especially quartz, has a high percentage of silicon in the form of silicon dioxide (SiO 2) and at the beginning production process is a basic component for creating semiconductors.Initially, SiO 2 is taken in the form of sand, which is reduced with coke in arc furnaces (at a temperature of about 1800°C):
These reactions, using the recycling of the resulting by-products containing silicon, reduce costs and eliminate environmental problems:
2SiHCl 3 SiH 2 Cl 2 + SiCl 4The resulting hydrogen can be used in many places, but the most important thing is that “electronic” silicon was obtained, pure, very pure (99.9999999%). A little later, a seed (“growth point”) is lowered into the melt of such silicon, which is gradually drawn out of the crucible. As a result, a so-called “boule” is formed - a single crystal as tall as an adult. The weight is appropriate - in production such a muzzle weighs about 100 kg.
2SiH 2 Cl 2 SiH 3 Cl + SiHCl 3
2SiH 3 Cl SiH 4 + SiH 2 Cl 2
SiH 4 Si + 2H 2
The ingot is sanded with a “zero” :) and cut with a diamond saw. The output is wafers (codenamed “wafer”) about 1 mm thick and 300 mm in diameter (~12 inches; these are the ones used for the 32nm process with HKMG, High-K/Metal Gate technology). Once upon a time, Intel used disks with a diameter of 50mm (2"), and in the near future they are already planning to switch to wafers with a diameter of 450mm - this is justified at least from the point of view of reducing the cost of producing chips. Speaking of savings - all these crystals are grown outside Intel; for processor production they are purchased elsewhere.
Each plate is polished, made perfectly smooth, bringing its surface to a mirror shine.
The production of chips consists of more than three hundred operations, as a result of which more than 20 layers form a complex three-dimensional structure - the volume of the article available on Habré will not allow us to briefly talk about even half of this list :) Therefore, very briefly and only about the most important stages.
So. It is necessary to transfer the structure of the future processor into polished silicon wafers, that is, introduce impurities into certain areas of the silicon wafer, which ultimately form transistors. How to do it? In general, application different layers It’s a whole science to apply to a processor, because even in theory such a process is not simple (not to mention in practice, taking into account the scale) ... but it’s so nice to understand the complex;) Well, or at least try to figure it out.
Photolithography
The problem is solved using photolithography technology - the process of selective etching of the surface layer using a protective photomask. The technology is built on the “light-template-photoresist” principle and proceeds as follows:- A layer of material is applied to the silicon substrate from which a pattern is to be formed. It is applied to it photoresist- a layer of polymer light-sensitive material that changes its physical and chemical properties when irradiated with light.The desired structure is drawn on a photomask - as a rule, this is a plate of optical glass on which opaque areas are photographically applied. Each such template contains one of the layers of the future processor, so it must be very accurate and practical.
- In production exposure(illumination of the photo layer for a precisely set period of time) through a photo mask
- Removal of spent photoresist.
Sometimes it is simply impossible to deposit certain materials in the right places on the plate, so it is much easier to apply the material to the entire surface at once, removing the excess from those places where it is not needed - the image above shows the application of photoresist in blue.
The wafer is irradiated by a stream of ions (positively or negatively charged atoms), which in given places penetrate under the surface of the wafer and change the conductive properties of silicon (green areas are embedded foreign atoms).
How to isolate areas that do not require further treatment? Before lithography on the surface of a silicon wafer (with high temperature in a special chamber) a protective dielectric film is applied - as I already said, instead of traditional silicon dioxide, Intel began to use High-K dielectric. It is thicker than silicon dioxide, but at the same time it has the same capacitive properties. Moreover, due to the increase in thickness, the leakage current through the dielectric is reduced, and as a result, it has become possible to obtain more energy-efficient processors. In general, it is much more difficult to ensure the uniformity of this film over the entire surface of the plate - in connection with this, high-precision temperature control is used in production.
So here it is. In those places that will be treated with impurities, a protective film is not needed - it is carefully removed using etching (removing areas of the layer to form a multilayer structure with certain properties). How can you remove it not everywhere, but only in the right areas? To do this, it is necessary to apply another layer of photoresist on top of the film - due to the centrifugal force of the rotating plate, it is applied in a very thin layer.
In photography, light passed through negative film, struck the surface of the photographic paper, and changed its chemical properties. In photolithography, the principle is similar: light is passed through a photomask onto a photoresist, and in those places where it passed through the mask, individual sections of the photoresist change properties. Light radiation is transmitted through the masks, which is focused on the substrate. For accurate focusing you need special system lenses or mirrors, capable of not only reducing the image cut out on the mask to the size of the chip, but also accurately projecting it on the workpiece. The printed wafers are typically four times smaller than the masks themselves.
All spent photoresist (which has changed its solubility under the influence of irradiation) is removed with a special chemical solution - along with it, part of the substrate under the illuminated photoresist also dissolves. The part of the substrate that was protected from light by the mask will not dissolve. It forms a conductor or future active element - the result of this approach is different circuit patterns on each layer of the microprocessor.
As a matter of fact, all the previous steps were necessary in order to create semiconductor structures in the required places by introducing a donor (n-type) or acceptor (p-type) impurity. Let's say we need to create a region of concentration of p-type carriers in silicon, that is, a hole conduction zone. To do this, the plate is processed using a device called implanter- boron ions with enormous energy are fired from a high-voltage accelerator and are evenly distributed in unprotected zones formed during photolithography.
Where the dielectric has been removed, the ions penetrate into the layer of unprotected silicon - otherwise they are “stuck” in the dielectric. After the next etching process, the remaining dielectric is removed, and zones remain on the plate in which there is local boron. It is clear that modern processors may have several such layers - in this case, a dielectric layer is again grown on the resulting picture and then everything follows the well-trodden path - another layer of photoresist, the photolithography process (using a new mask), etching, implantation... you know understood.
The characteristic size of the transistor is now 32 nm, and the wavelength with which silicon is processed is not even ordinary light, but a special ultraviolet excimer laser - 193 nm. However, the laws of optics do not allow resolving two objects located at a distance of less than half a wavelength. This happens due to diffraction of light. What should I do? Use various tricks - for example, in addition to the mentioned excimer lasers, which shine far in the ultraviolet spectrum, modern photolithography uses multilayer reflective optics using special masks and a special process of immersion (submersible) photolithography.
Logic elements that are formed during the photolithography process must be connected to each other. To do this, the plates are placed in a solution of copper sulfate, in which, under the influence of an electric current, metal atoms “settle” in the remaining “passages” - as a result of this galvanic process, conductive areas are formed, creating connections between in separate parts processor "logic". Excess conductive coating is removed by polishing.
Finish line
Hurray – the hardest part is over. Left in a cunning way connect the “remains” of transistors - the principle and sequence of all these connections (buses) is called processor architecture. These connections are different for each processor - although the circuits seem completely flat, in some cases up to 30 levels of such “wires” can be used. From a distance (at a very high magnification) all this looks like a futuristic road junction - and after all, someone is designing these tangles!
When wafer processing is completed, the wafers are transferred from production to the assembly and testing shop. There, the crystals undergo the first tests, and those that pass the test (and this is the vast majority) are cut from the substrate with a special device.
At the next stage, the processor is packaged into a substrate (in the figure - processor Intel Core i5, consisting of a CPU and an HD graphics chip).
Hello socket!
The substrate, crystal and heat distribution cover are connected together - this is the product we mean when we say the word “processor”. The green substrate creates an electrical and mechanical interface (gold is used to electrically connect the silicon chip to the case), thanks to which it will be possible to install the processor into the motherboard socket - in fact, this is just a platform on which the contacts from the small chip are routed. The heat distribution cover is a thermal interface that cools the processor during operation - it is to this cover that the cooling system will be attached, be it a cooler radiator or a healthy water block.
Socket(connector central processor) - a female or slot connector designed for installing a central processor. Using a connector instead of directly soldering the processor to motherboard Makes it easy to replace the processor to upgrade or repair your computer. The connector can be intended for installing the processor itself or a CPU card (for example, in Pegasos). Each slot allows installation of only a certain type of processor or CPU card.
At the final stage of production, finished processors undergo final tests to ensure they meet the basic characteristics - if everything is in order, then the processors are sorted in the required order into special trays - in this form the processors will go to manufacturers or go on sale to OEMs. Another batch will be sold as BOX versions - in a beautiful box along with the stock cooling system.
The end
Now imagine that a company announces, for example, 20 new processors. They are all different from each other - the number of cores, cache sizes, supported technologies... Each processor model uses a certain number of transistors (counting in millions and even billions), its own principle of connecting elements... And all this must be designed and created/automated - templates, lenses, lithography, hundreds of parameters for each process, testing... And all this should work around the clock, in several factories at once... As a result, devices should appear that have no room for error in operation... And the cost of these technological masterpieces should be within the bounds of decency... Almost sure The point is that you, like me, also cannot imagine the full scope of the work being done, which I tried to talk about today.Well, and something more surprising. Imagine that in five minutes you are a great scientist - you carefully removed the heat distribution cover of the processor and through a huge microscope you were able to see the structure of the processor - all these connections, transistors... you even sketched something on a piece of paper so as not to forget. Do you think it’s easy to study the principles of a processor’s operation, having only this data and data about what tasks can be solved using this processor? It seems to me that approximately this picture is now visible to scientists who are trying to study the work at a similar level human brain. Only if you believe Stanford microbiologists, in one human brain
As promised - a detailed story about how processors are made... starting with sand. Everything you wanted to know but were afraid to ask)
I have already talked about “ Where are processors made?" and about what " Production difficulties"are on this path. Today we will talk directly about the production itself – “from start to finish.”
Processor production
When a factory for the production of processors using a new technology is built, it has 4 years to recoup the investment (more than $5 billion) and make a profit. From simple secret calculations it turns out that the factory must produce at least 100 working wafers per hour.Briefly, the process of manufacturing a processor looks like this: a cylindrical single crystal is grown from molten silicon using special equipment. The resulting ingot is cooled and cut into “pancakes,” the surface of which is carefully leveled and polished to a mirror shine. Then, in the “clean rooms” of semiconductor factories, integrated circuits are created on silicon wafers using photolithography and etching. After re-cleaning the wafers, laboratory specialists perform selective testing of the processors under a microscope - if everything is “OK”, then the finished wafers are cut into individual processors, which are later enclosed in housings.
Chemistry lessons
Let's look at the whole process in more detail. The silicon content in the earth's crust is about 25-30% by weight, making this element second in abundance after oxygen. Sand, especially quartz sand, has a high percentage of silicon in the form of silicon dioxide (SiO2) and is a basic component for creating semiconductors early in the manufacturing process.Initially, SiO 2 is taken in the form of sand, which is reduced with coke in arc furnaces (at a temperature of about 1800°C):
These reactions, using the recycling of the resulting by-products containing silicon, reduce costs and eliminate environmental problems:
2SiHCl 3 SiH 2 Cl 2 + SiCl 4The resulting hydrogen can be used in many places, but the most important thing is that “electronic” silicon was obtained, pure, very pure (99.9999999%). A little later, a seed (“growth point”) is lowered into the melt of such silicon, which is gradually drawn out of the crucible. As a result, a so-called “boule” is formed - a single crystal as tall as an adult. The weight is appropriate - in production such a muzzle weighs about 100 kg.
2SiH 2 Cl 2 SiH 3 Cl + SiHCl 3
2SiH 3 Cl SiH 4 + SiH 2 Cl 2
SiH 4 Si + 2H 2
The ingot is sanded with a “zero” :) and cut with a diamond saw. The output is wafers (codenamed “wafer”) about 1 mm thick and 300 mm in diameter (~12 inches; these are the ones used for the 32nm process with HKMG, High-K/Metal Gate technology). Once upon a time, Intel used disks with a diameter of 50mm (2"), and in the near future they are already planning to switch to wafers with a diameter of 450mm - this is justified at least from the point of view of reducing the cost of producing chips. Speaking of savings - all these crystals are grown outside Intel; for processor production they are purchased elsewhere.
Each plate is polished, made perfectly smooth, bringing its surface to a mirror shine.
The production of chips consists of more than three hundred operations, as a result of which more than 20 layers form a complex three-dimensional structure - the volume of the article available on Habré will not allow us to briefly talk about even half of this list :) Therefore, very briefly and only about the most important stages.
So. It is necessary to transfer the structure of the future processor into polished silicon wafers, that is, introduce impurities into certain areas of the silicon wafer, which ultimately form transistors. How to do it? In general, applying various layers to a processor substrate is a whole science, because even in theory such a process is not simple (not to mention in practice, taking into account the scale) ... but it’s so nice to understand the complex;) Well, or at least try to figure it out.
Photolithography
The problem is solved using photolithography technology - the process of selective etching of the surface layer using a protective photomask. The technology is built on the “light-template-photoresist” principle and proceeds as follows:- A layer of material is applied to the silicon substrate from which a pattern is to be formed. It is applied to it photoresist- a layer of polymer light-sensitive material that changes its physical and chemical properties when irradiated with light.The desired structure is drawn on a photomask - as a rule, this is a plate of optical glass on which opaque areas are photographically applied. Each such template contains one of the layers of the future processor, so it must be very accurate and practical.
- In production exposure(illumination of the photo layer for a precisely set period of time) through a photo mask
- Removal of spent photoresist.
Sometimes it is simply impossible to deposit certain materials in the right places on the plate, so it is much easier to apply the material to the entire surface at once, removing the excess from those places where it is not needed - the image above shows the application of photoresist in blue.
The wafer is irradiated by a stream of ions (positively or negatively charged atoms), which in given places penetrate under the surface of the wafer and change the conductive properties of silicon (green areas are embedded foreign atoms).
How to isolate areas that do not require further treatment? Before lithography, a protective film of dielectric is applied to the surface of the silicon wafer (at high temperature in a special chamber) - as I already said, instead of traditional silicon dioxide, Intel began to use High-K dielectric. It is thicker than silicon dioxide, but at the same time it has the same capacitive properties. Moreover, due to the increase in thickness, the leakage current through the dielectric is reduced, and as a result, it has become possible to obtain more energy-efficient processors. In general, it is much more difficult to ensure the uniformity of this film over the entire surface of the plate - in connection with this, high-precision temperature control is used in production.
So here it is. In those places that will be treated with impurities, a protective film is not needed - it is carefully removed using etching (removing areas of the layer to form a multilayer structure with certain properties). How can you remove it not everywhere, but only in the right areas? To do this, it is necessary to apply another layer of photoresist on top of the film - due to the centrifugal force of the rotating plate, it is applied in a very thin layer.
In photography, light passed through negative film, struck the surface of the photographic paper, and changed its chemical properties. In photolithography, the principle is similar: light is passed through a photomask onto a photoresist, and in those places where it passed through the mask, individual sections of the photoresist change properties. Light radiation is transmitted through the masks, which is focused on the substrate. For precise focusing, a special system of lenses or mirrors is required, which can not only reduce the image cut out on the mask to the size of the chip, but also accurately project it on the workpiece. The printed wafers are typically four times smaller than the masks themselves.
All spent photoresist (which has changed its solubility under the influence of irradiation) is removed with a special chemical solution - along with it, part of the substrate under the illuminated photoresist also dissolves. The part of the substrate that was protected from light by the mask will not dissolve. It forms a conductor or future active element - the result of this approach is different circuit patterns on each layer of the microprocessor.
As a matter of fact, all the previous steps were necessary in order to create semiconductor structures in the required places by introducing a donor (n-type) or acceptor (p-type) impurity. Let's say we need to create a region of concentration of p-type carriers in silicon, that is, a hole conduction zone. To do this, the plate is processed using a device called implanter- boron ions with enormous energy are fired from a high-voltage accelerator and are evenly distributed in unprotected zones formed during photolithography.
Where the dielectric has been removed, the ions penetrate into the layer of unprotected silicon - otherwise they are “stuck” in the dielectric. After the next etching process, the remaining dielectric is removed, and zones remain on the plate in which there is local boron. It is clear that modern processors may have several such layers - in this case, a dielectric layer is again grown on the resulting picture and then everything follows the well-trodden path - another layer of photoresist, the photolithography process (using a new mask), etching, implantation... you know understood.
The characteristic size of the transistor is now 32 nm, and the wavelength with which silicon is processed is not even ordinary light, but a special ultraviolet excimer laser - 193 nm. However, the laws of optics do not allow resolving two objects located at a distance of less than half a wavelength. This happens due to diffraction of light. What should I do? Use various tricks - for example, in addition to the mentioned excimer lasers, which shine far in the ultraviolet spectrum, modern photolithography uses multilayer reflective optics using special masks and a special process of immersion (submersible) photolithography.
Logic elements that are formed during the photolithography process must be connected to each other. To do this, the plates are placed in a solution of copper sulfate, in which, under the influence of an electric current, metal atoms “settle” in the remaining “passages” - as a result of this galvanic process, conductive areas are formed, creating connections between individual parts of the processor “logic”. Excess conductive coating is removed by polishing.
Finish line
Hurray – the hardest part is over. All that remains is a cunning way to connect the “remains” of transistors - the principle and sequence of all these connections (buses) is called processor architecture. These connections are different for each processor - although the circuits seem completely flat, in some cases up to 30 levels of such “wires” can be used. From a distance (at a very high magnification) all this looks like a futuristic road junction - and after all, someone is designing these tangles!
When wafer processing is completed, the wafers are transferred from production to the assembly and testing shop. There, the crystals undergo the first tests, and those that pass the test (and this is the vast majority) are cut from the substrate with a special device.
At the next stage, the processor is packaged into a substrate (in the picture - an Intel Core i5 processor, consisting of a CPU and an HD graphics chip).
Hello socket!
The substrate, crystal and heat distribution cover are connected together - this is the product we mean when we say the word “processor”. The green substrate creates an electrical and mechanical interface (gold is used to electrically connect the silicon chip to the case), thanks to which it will be possible to install the processor into the motherboard socket - in fact, this is just a platform on which the contacts from the small chip are routed. The heat distribution cover is a thermal interface that cools the processor during operation - it is to this cover that the cooling system will be attached, be it a cooler radiator or a healthy water block.
Socket(CPU socket) - a female or slot connector designed to install a central processor. Using a socket instead of directly soldering the processor to the motherboard makes it easier to replace the processor to upgrade or repair your computer. The connector can be intended for installing the processor itself or a CPU card (for example, in Pegasos). Each slot allows installation of only a certain type of processor or CPU card.
At the final stage of production, finished processors undergo final tests to ensure they meet the basic characteristics - if everything is in order, then the processors are sorted in the required order into special trays - in this form the processors will go to manufacturers or go on sale to OEMs. Another batch will be sold as BOX versions - in a beautiful box along with the stock cooling system.
The end
Now imagine that a company announces, for example, 20 new processors. They are all different from each other - the number of cores, cache sizes, supported technologies... Each processor model uses a certain number of transistors (counting in millions and even billions), its own principle of connecting elements... And all this must be designed and created/automated - templates, lenses, lithography, hundreds of parameters for each process, testing... And all this should work around the clock, in several factories at once... As a result, devices should appear that have no room for error in operation... And the cost of these technological masterpieces should be within the bounds of decency... Almost sure The point is that you, like me, also cannot imagine the full scope of the work being done, which I tried to talk about today.Well, and something more surprising. Imagine that in five minutes you are a great scientist - you carefully removed the heat distribution cover of the processor and through a huge microscope you were able to see the structure of the processor - all these connections, transistors... you even sketched something on a piece of paper so as not to forget. Do you think it’s easy to study the principles of a processor’s operation, having only this data and data about what tasks can be solved using this processor? It seems to me that approximately this picture is now visible to scientists who are trying to study the functioning of the human brain at a similar level. Only if you believe Stanford microbiologists, in one human brain
Modern microprocessors are among the most complex devices manufactured by man. Production semiconductor crystal much more resource-intensive than, say, building a multi-story building or organizing a major exhibition event. However, thanks to the mass production of CPUs in monetary terms, we do not notice this, and rarely does anyone think about the enormity of the elements that occupy such a prominent place inside the system unit. We decided to study the details of processor production and talk about them in this material. Fortunately, there is enough information on this topic on the Internet today, and a specialized selection of presentations and slides from Intel Corporation allows you to complete the task as clearly as possible. The enterprises of other giants of the semiconductor industry work on the same principle, so we can confidently say that all modern microcircuits go through an identical creation path.
 |
 |
 |
 |
 |
 |
 |
 |
The first thing worth mentioning is the building material for processors. Silicon is the second most common element on the planet after oxygen. It is a natural semiconductor and is used as the main material for the production of chips of various microcircuits. Most silicon is found in ordinary sand (especially quartz) in the form of silicon dioxide (SiO2).
However, silicon is not the only material. Its closest relative and substitute is germanium, but in the process of improving production, scientists are identifying good semiconductor properties in compounds of other elements and are preparing to test them in practice or are already doing so.
1 Silicon goes through a multi-stage purification process: raw materials for microcircuits cannot contain more impurities than one foreign atom per billion.
2 Silicon is melted in a special container and, having lowered a constantly cooled rotating rod inside, the substance is “wound” around it thanks to surface tension forces.
3 The result is longitudinal blanks (single crystals) of circular cross-section, each weighing about 100 kg.
4 The workpiece is cut into individual silicon disks - wafers, on which hundreds of microprocessors will be located. For these purposes, machines with diamond cutting discs or wire-abrasive installations are used.
5 The substrates are polished to a mirror finish to eliminate all surface defects. The next step is applying the thinnest photopolymer layer.
6 The treated substrate is exposed to harsh ultraviolet radiation. A chemical reaction occurs in the photopolymer layer: light, passing through numerous stencils, repeats the patterns of the CPU layers.
7 Actual size The applied image is several times smaller than the stencil itself.
8 Areas “etched” by radiation are washed away. A pattern is obtained on the silicon substrate, which is then bonded.
9 The next stage in the manufacture of one layer is ionization, during which polymer-free areas of silicon are bombarded with ions.
10 In places where they hit, the properties of electrical conductivity change.
11 The remaining polymer is removed and the transistor is almost complete. Holes are made in the insulating layers, which, thanks to a chemical reaction, are filled with copper atoms used as contacts.
12 The connection of transistors is a multi-level wiring. If you look through a microscope, you will notice on the crystal many metal conductors and silicon atoms placed between them or its modern substitutes.
13 Part of the finished substrate undergoes the first functionality test. At this stage, current is applied to each of the selected transistors, and automated system checks the operating parameters of the semiconductor.
14 The substrate is cut into separate parts using the thinnest cutting wheels.
15 The usable crystals obtained as a result of this operation are used in the production of processors, and the defective ones are sent to waste.
16 A separate chip from which the processor will be made is placed between the base (substrate) of the CPU and the heat distribution cover and “packed”.
17 During final testing, finished processors are checked for compliance with the required parameters and only then are sorted. Based on the data received, microcode is flashed into them, allowing the system to properly identify the CPU.
18 The finished devices are packaged and sent to the market.
 |
 |
 |
 |
Interesting facts about processors and their production
"Silicon Valley" (Silicon Valley, USA, California)
It got its name from the main building element used in the production of microchips.
“Why are processor wafers round?”- you will probably ask.
To produce silicon crystals, a technology is used that makes it possible to obtain only cylindrical blanks, which are then cut into pieces. Until now, no one has been able to produce a square plate free of defects.
Why are microchips square?
It is this type of lithography that allows the wafer area to be used with maximum efficiency.
Why do processors need so many pins/pins?
In addition to signal lines, each processor requires stable power to operate. With a power consumption of about 100-120 W and low voltage, a current of up to 100 A can flow through the contacts. A significant part of the CPU contacts is dedicated specifically to the power supply system and is duplicated.
Disposal of production waste
Previously, defective wafers, their remains and defective microchips went to waste. Today, developments are underway to use them as a basis for the production of solar cells.
"Bunny Costume"
This is the name given to the jumpsuit. white which all production facility workers are required to wear. This is done to maintain maximum cleanliness and protect against accidental entry of dust particles into production facilities. The "bunny suit" was first used in processor factories in 1973 and has since become an accepted standard.
99,9999%
Only silicon is suitable for the production of processors of the highest degree cleanliness. The workpieces are cleaned with special chemicals.
300 mm
This is the diameter of modern silicon wafers for the production of processors.
1000 times
This is how much cleaner the air is in the premises of chip factories than in the operating room.
20 layers
The processor chip is very thin (less than a millimeter), but it contains more than 20 layers of complex structural combinations of transistors that look like multi-level highways.
2500
Exactly how many processor crystals Intel Atom(have the smallest area among modern CPUs) are placed on one 300 mm wafer.
10 000 000 000 000 000 000
One hundred quintillion transistors, the building blocks of microchips, are shipped from factories every year. This is approximately 100 times more than the estimated number of ants on the planet.
A
The cost of producing one transistor in a processor today is equal to the cost of printing one letter in a newspaper.
In the process of preparing this article, materials were used from the official website of Intel Corporation, www.intel.ua
How are microcircuits made?
To understand what the main difference between these two technologies is, it is necessary to take a brief excursion into the very technology of production of modern processors or integrated circuits.
As is known from the school physics course, in modern electronics The main components of integrated circuits are p-type and n-type semiconductors (depending on the type of conductivity). A semiconductor is a substance whose conductivity is superior to dielectrics, but inferior to metals. The basis of both types of semiconductors can be silicon (Si), which in its pure form (the so-called intrinsic semiconductor) conducts poorly electricity However, the addition (introduction) of a certain impurity into silicon can radically change its conductive properties. There are two types of impurities: donor and acceptor. The donor impurity leads to the formation of n-type semiconductors with electronic type of conductivity, and the acceptor one leads to the formation of p-type semiconductors with hole type conductivity. Contacts of p- and n-semiconductors allow the formation of transistors basic structural elements modern microcircuits. These transistors, called CMOS transistors, can exist in two basic states: open, when they conduct electricity, and off, when they do not conduct electricity. Since CMOS transistors are the main elements of modern microcircuits, let's talk about them in more detail.
How does a CMOS transistor work?
The simplest n-type CMOS transistor has three electrodes: source, gate and drain. The transistor itself is made of a p-type semiconductor with hole conductivity, and n-type semiconductors with electronic conductivity are formed in the drain and source regions. Naturally, due to the diffusion of holes from the p-region to the n-region and the reverse diffusion of electrons from the n-region to the p-region, depletion layers (layers in which there are no major charge carriers) are formed at the boundaries of the transitions of the p- and n-regions. IN normal condition, that is, when no voltage is applied to the gate, the transistor is in a “locked” state, that is, it is not able to conduct current from source to drain. The situation does not change even if a voltage is applied between the drain and the source (we do not take into account the leakage currents caused by the movement under the influence of the generated electric fields of non-fundamental charge carriers, that is, holes for the n-region and electrons for the p-region).
However, if a positive potential is applied to the gate (Fig. 1), the situation will change radically. Under the influence of the gate's electric field, holes are pushed deep into the p-semiconductor, and electrons, on the contrary, are drawn into the area under the gate, forming an electron-rich channel between the source and drain. If a positive voltage is applied to the gate, these electrons begin to move from source to drain. In this case, the transistor conducts current; the transistor is said to “open.” If the gate voltage is removed, electrons stop being drawn into the area between the source and drain, the conducting channel is destroyed and the transistor stops passing current, that is, it “turns off.” Thus, by changing the gate voltage, you can open or close the transistor, similar to how you can turn a regular toggle switch on or off, controlling the flow of current through the circuit. This is why transistors are sometimes called electronic switches. However, unlike conventional mechanical switches, CMOS transistors are virtually inertia-free and are capable of switching from on to off trillions of times per second! It is this characteristic, that is, the ability to instantaneously switch, that ultimately determines the performance of the processor, which consists of tens of millions of such simple transistors.
So, modern integrated circuit consists of tens of millions of simple CMOS transistors. Let us dwell in more detail on the process of manufacturing microcircuits, the first stage of which is the production of silicon substrates.
Step 1. Growing blanks
The creation of such substrates begins with growing a cylindrical silicon single crystal. Subsequently, these monocrystalline blanks (blanks) are cut into round wafers (wafers), the thickness of which is approximately 1/40 inch and the diameter is 200 mm (8 inches) or 300 mm (12 inches). These are the silicon substrates used for the production of microcircuits.
When forming wafers from silicon single crystals, the fact that for ideal crystal structures the physical properties largely depend on the chosen direction (anisotropy property) is taken into account. For example, the resistance of a silicon substrate will be different in the longitudinal and transverse directions. Likewise, depending on the orientation of the crystal lattice, a silicon crystal will react differently to any external influences related to its further processing (for example, etching, sputtering, etc.). Therefore, the plate must be cut from a single crystal in such a way that the orientation of the crystal lattice relative to the surface is strictly maintained in a certain direction.
As already noted, the diameter of the silicon single crystal workpiece is either 200 or 300 mm. Moreover, the diameter is 300 mm this is relative new technology, which we will discuss below. It is clear that a plate of this diameter can accommodate more than one microcircuit, even if we are talking about Intel processor Pentium 4. Indeed, several dozen microcircuits (processors) are formed on one such substrate plate, but for simplicity we will consider only the processes occurring in a small area of one future microprocessor.
Step 2. Applying a protective film of dielectric (SiO2)
After the formation of the silicon substrate, the stage of creating a complex semiconductor structure begins.
To do this, it is necessary to introduce so-called donor and acceptor impurities into silicon. However, the question arises: how to introduce impurities according to a precisely specified pattern? To make this possible, those areas where impurities do not need to be introduced are protected with a special film of silicon dioxide, leaving only those areas exposed that are subject to further processing (Fig. 2). The process of forming such a protective film of the desired pattern consists of several stages.
At the first stage, the entire silicon wafer is completely covered with a thin film of silicon dioxide (SiO2), which is a very good insulator and acts as a protective film during further processing of the silicon crystal. The wafers are placed in a chamber where, at high temperature (from 900 to 1100 °C) and pressure, oxygen diffuses into the surface layers of the wafers, leading to the oxidation of silicon and the formation of a surface film of silicon dioxide. In order for the silicon dioxide film to have a precisely specified thickness and be free of defects, it is necessary to strictly maintain a constant temperature at all points of the wafer during the oxidation process. If not the entire wafer is to be covered with a silicon dioxide film, then a Si3N4 mask is first applied to the silicon substrate to prevent unwanted oxidation.
Step 3. Applying photoresist
After the silicon substrate is coated protective film silicon dioxide, it is necessary to remove this film from those places that will be subjected to further processing. The film is removed by etching, and to protect the remaining areas from etching, a layer of so-called photoresist is applied to the surface of the wafer. The term “photoresists” refers to compounds that are light-sensitive and resistant to aggressive factors. The compositions used must have, on the one hand, certain photographic properties (under the influence of ultraviolet light they become soluble and are washed out during the etching process), and on the other, resistive, allowing them to withstand etching in acids and alkalis, heating, etc. The main purpose of photoresists is to create a protective relief of the desired configuration.
The process of applying photoresist and its further irradiation with ultraviolet light according to a given pattern is called photolithography and includes the following basic operations: formation of a photoresist layer (substrate processing, application, drying), formation of a protective relief (exposure, development, drying) and transfer of the image to the substrate (etching, sputtering etc.).
Before applying a layer of photoresist (Fig. 3) to the substrate, the latter is subjected to pre-treatment, as a result of which its adhesion to the photoresist layer improves. To apply a uniform layer of photoresist, the centrifugation method is used. The substrate is placed on a rotating disk (centrifuge), and under the influence of centrifugal forces, the photoresist is distributed over the surface of the substrate in an almost uniform layer. (When talking about an almost uniform layer, we take into account the fact that under the influence of centrifugal forces, the thickness of the resulting film increases from the center to the edges, however, this method of applying photoresist can withstand fluctuations in the layer thickness within ±10%.)
Step 4. Lithography
After applying and drying the photoresist layer, the stage of formation of the necessary protective relief begins. The relief is formed as a result of the fact that under the influence of ultraviolet radiation falling on certain areas of the photoresist layer, the latter changes the solubility properties, for example, the illuminated areas cease to dissolve in the solvent, which remove areas of the layer that were not exposed to illumination, or vice versa - the illuminated areas dissolve. Based on the method of relief formation, photoresists are divided into negative and positive. Negative photoresists, when exposed to ultraviolet radiation, form protective relief areas. Positive photoresists, on the contrary, under the influence of ultraviolet radiation acquire fluidity properties and are washed out by the solvent. Respectively protective layer is formed in those areas that are not exposed to ultraviolet irradiation.
To illuminate the desired areas of the photoresist layer, a special mask template is used. Most often, optical glass plates with opaque elements obtained photographically or otherwise are used for this purpose. In fact, such a template contains a drawing of one of the layers of the future microcircuit (there can be several hundred such layers in total). Since this template is a reference, it must be made with great precision. In addition, taking into account the fact that many photo plates will be made from one photomask, it must be durable and resistant to damage. From this it is clear that a photomask is a very expensive thing: depending on the complexity of the microcircuit, it can cost tens of thousands of dollars.
Ultraviolet radiation, passing through such a template (Fig. 4), illuminates only the necessary areas of the surface of the photoresist layer. After irradiation, the photoresist undergoes development, as a result of which unnecessary areas of the layer are removed. This exposes the corresponding part of the silicon dioxide layer.
Despite the apparent simplicity of the photolithographic process, it is this stage of microcircuit production that is the most complex. The fact is that, in accordance with Moore's prediction, the number of transistors on one chip increases exponentially (doubles every two years). Such an increase in the number of transistors is only possible due to a decrease in their size, but it is precisely the decrease that “rests” on the lithography process. In order to make transistors smaller, it is necessary to reduce the geometric dimensions of the lines applied to the photoresist layer. But there is a limit to everything; focusing a laser beam to a point is not so easy. The fact is that according to the laws wave optics minimum size The spot into which the laser beam is focused (in fact, it is not just a spot, but a diffraction pattern) is determined, among other factors, by the wavelength of the light. The development of lithographic technology since its invention in the early 70s has been in the direction of reducing the wavelength of light. This is what made it possible to reduce the size of the elements integrated circuit. Since the mid-80s, photolithography began to use ultraviolet radiation produced by laser. The idea is simple: the wavelength of ultraviolet radiation is shorter than the wavelength of visible light, therefore it is possible to obtain finer lines on the surface of the photoresist. Until recently, lithography used deep ultraviolet radiation (DUV) with a wavelength of 248 nm. However, when photolithography moved beyond 200 nm, serious problems arose that for the first time cast doubt on the continued use of this technology. For example, at wavelengths less than 200 microns, too much light is absorbed by the photosensitive layer, thereby complicating and slowing down the process of transferring the circuit template to the processor. Problems such as these are prompting researchers and manufacturers to look for alternatives to traditional lithography technology.
The new lithography technology, called EUV lithography (Extreme UltraViolet ultra-hard ultraviolet radiation), is based on the use of ultraviolet radiation with a wavelength of 13 nm.
The transition from DUV to EUV lithography provides a more than 10-fold reduction in wavelength and a transition to a range where it is comparable to the size of only a few tens of atoms.
The lithography technology currently in use allows a template to be applied with a minimum conductor width of 100 nm, while EUV lithography makes possible printing lines of much smaller width up to 30 nm. Controlling ultrashort radiation is not as easy as it seems. Since EUV radiation is well absorbed by glass, the new technology involves the use of a series of four special convex mirrors that reduce and focus the image obtained after applying the mask (Fig. 5, ,). Each such mirror contains 80 individual metal layers approximately 12 atoms thick.
Step 5: Etching
After exposing the photoresist layer, the etching stage begins to remove the silicon dioxide film (Fig. 8).
The etching process is often associated with acid baths. This acid etching method is well known to radio amateurs who have made their own printed circuit boards. To do this, a pattern of tracks for the future board is applied to the foil-coated PCB with varnish, which acts as a protective layer, and then the plate is lowered into a bath of nitric acid. Unnecessary sections of the foil are etched off, exposing clean PCB. This method has a number of disadvantages, the main one of which is the inability to accurately control the layer removal process, since too many factors influence the etching process: acid concentration, temperature, convection, etc. In addition, the acid interacts with the material in all directions and gradually penetrates under the edge of the photoresist mask, that is, it destroys the layers covered with the photoresist from the side. Therefore, in the production of processors, the dry etching method, also called plasma, is used. This method allows precise control of the etching process, and the destruction of the etched layer occurs strictly in the vertical direction.
Dry etching uses an ionized gas (plasma) to remove silicon dioxide from the wafer surface, which reacts with the silicon dioxide surface to produce volatile byproducts.
After the etching procedure, that is, when the desired areas of pure silicon are exposed, the remaining part of the photolayer is removed. Thus, a pattern made by silicon dioxide remains on the silicon substrate.
Step 6. Diffusion (ion implantation)
Let us recall that the previous process of forming the required pattern on a silicon substrate was required in order to create semiconductor structures in the right places by introducing a donor or acceptor impurity. The process of introducing impurities is carried out through diffusion (Fig. 9) uniform introduction of impurity atoms into the silicon crystal lattice. To obtain an n-type semiconductor, antimony, arsenic or phosphorus are usually used. To obtain a p-type semiconductor, boron, gallium or aluminum are used as impurities.
Ion implantation is used for the process of dopant diffusion. The implantation process consists of ions of the desired impurity being “shot” from a high-voltage accelerator and, having sufficient energy, penetrating into the surface layers of silicon.
So, at the end of the ion implantation stage, the necessary layer of the semiconductor structure has been created. However, in microprocessors there may be several such layers. To create the next layer in the resulting circuit pattern, an additional thin layer of silicon dioxide is grown. After this, a layer of polycrystalline silicon and another layer of photoresist are deposited. Ultraviolet radiation is passed through the second mask and highlights the corresponding pattern on the photo layer. Then again the stages of dissolving the photolayer, etching and ion implantation follow.
Step 7. Sputtering and deposition
The application of new layers is carried out several times, while for interlayer connections “windows” are left in the layers, which are filled with metal atoms; As a result, metal strips conducting regions are created on the crystal. Thus in modern processors connections are established between layers that form a complex three-dimensional circuit. The process of growing and processing all layers lasts several weeks, and the production cycle itself consists of more than 300 stages. As a result, hundreds of identical processors are formed on a silicon wafer.
To withstand the impacts that the wafers are exposed to during the layering process, the silicon wafers are initially made quite thick. Therefore, before cutting the wafer into individual processors, its thickness is reduced by 33% and contamination is removed from reverse side. Then a layer of special material is applied to the back side of the substrate to improve the attachment of the crystal to the body of the future processor.
Step 8. Final stage
At the end of the formation cycle, all processors are thoroughly tested. Then from the substrate plate using special device specific crystals that have already passed the test are cut out (Fig. 10).
Each microprocessor is built into protective housing, which also provides electrical connection between the microprocessor chip and external devices. The type of housing depends on the type and intended application of the microprocessor.
After sealing in the case, each microprocessor is retested. Faulty processors are rejected, and working ones are subjected to load tests. Processors are then sorted based on their behavior at different clock speeds and supply voltages.
Promising technologies
We have considered the technological process of producing microcircuits (in particular, processors) in a very simplified manner. But even such a superficial presentation allows us to understand the technological difficulties encountered when reducing the size of transistors.
However, before considering new promising technologies, let’s answer the question posed at the very beginning of the article: what is the design standard of the technological process and how, in fact, does the design standard of 130 nm differ from the standard of 180 nm? 130 nm or 180 nm this is the characteristic minimum distance between two adjacent elements in one layer of the microcircuit, that is, a kind of grid step to which the elements of the microcircuit are linked. It is quite obvious that the smaller this characteristic size, the more transistors can be placed on the same area of the microcircuit.
Currently, Intel processors use a 0.13-micron process technology. The processor is manufactured using this technology Intel Pentium 4 with Northwood core, Intel Pentium III processor with Tualatin core and processor Intel Celeron. When using such a technological process, the useful channel width of the transistor is 60 nm, and the thickness of the gate oxide layer does not exceed 1.5 nm. In total, the Intel Pentium 4 processor contains 55 million transistors.
Along with increasing the density of transistors in the processor chip, the 0.13-micron technology, which replaced the 0.18-micron technology, has other innovations. Firstly, it uses copper connections between individual transistors (in 0.18-micron technology the connections were aluminum). Secondly, 0.13-micron technology provides lower power consumption. For mobile equipment, for example, this means that the power consumption of microprocessors becomes less, and the operating time from battery more.
Well latest innovation, which was implemented during the transition to a 0.13-micron technological process this is the use of silicon wafers (wafer) with a diameter of 300 mm. Let us recall that before this, most processors and microcircuits were manufactured on the basis of 200 mm wafers.
Increasing the diameter of the wafer makes it possible to reduce the cost of each processor and increase the yield of products of adequate quality. Indeed, the area of a wafer with a diameter of 300 mm is 2.25 times larger than the area of a wafer with a diameter of 200 mm, and accordingly, the number of processors obtained from one wafer with a diameter of 300 mm is more than twice as large.
In 2003, a new technological process with an even smaller design standard is expected to be introduced, namely 90-nanometer. The new process by which Intel will manufacture most of its products, including processors, chipsets and communications equipment, was developed at Intel's D1C 300mm wafer pilot plant in Hillsboro, Oregon.
On October 23, 2002, Intel announced the opening of a new $2 billion facility in Rio Rancho, New Mexico. The new plant, called F11X, will use modern technology, which will produce processors on 300 mm wafers using a process technology with a design norm of 0.13 microns. In 2003, the plant will be transferred to a technological process with a design standard of 90 nm.
In addition, Intel has already announced the resumption of construction of another production facility at Fab 24 in Leixlip (Ireland), which is designed to produce semiconductor components on 300 mm silicon wafers with a 90 nm design standard. A new enterprise with a total area of more than 1 million square meters. feet with especially clean rooms with an area of 160 thousand square meters. ft. is expected to be operational in the first half of 2004 and will employ more than a thousand employees. The cost of the facility is about 2 billion dollars.
The 90nm process uses a range of advanced technologies. These are the world's smallest mass-produced CMOS transistors with a gate length of 50 nm (Fig. 11), which provides increased performance while reducing power consumption, and the thinnest gate oxide layer of any transistor ever produced - only 1.2 nm (Fig. 12), or less than 5 atomic layers, and the industry's first implementation of high-performance strained silicon technology.
Of the listed characteristics, perhaps only the concept of “strained silicon” needs comment (Fig. 13). In such silicon, the distance between atoms is greater than in a conventional semiconductor. This, in turn, allows current to flow more freely, similar to how traffic moves more freely and faster on a road with wider lanes.
As a result of all innovations, the performance characteristics of transistors are improved by 10-20%, while increasing production costs by only 2%.
Additionally, the 90nm process uses seven layers on the chip (Figure 14), one layer more than the 130nm process, as well as copper interconnects.
All these features, combined with 300mm silicon wafers, provide Intel with benefits in performance, production volume and cost. Consumers also benefit, since the new technological Intel process allows the industry to continue to evolve in accordance with Moore's Law, increasing processor performance again and again.