This may seem like a silly question that can be answered in one sentence: Silicon is element 14 on the periodic table. However, silicon is mentioned more often than others on electronics sites because it is not only the main component of most building materials, but also the basis for modern computer processors, and even the most likely candidate for the role of the basic element of "non-carbon life". What does silicon do special?
Silicon as a building material
After oxygen, silicon is the most common element in the earth's crust, but finding it is not so easy, because it is almost never found in its pure form. The most common in nature is silicate SiO4 or silicon dioxide SiO2. Silica is also the main component of sand. Feldspar, granite, quartz - they are all based on a combination of silicon and oxygen.
Silicon compounds have a wide range of useful properties, mainly because they can bind other atoms very tightly in complex structures. Various silicates, such as calcium silicate, are the main constituent of cement, the main binder of concrete and even plaster. Some silicate materials are used in ceramics, and of course glass. In addition, silicon is added to substances such as cast iron to make the alloy more durable.
And, yes, silicon is also the main structural component of the synthetic material silicone, which is why silicone (silicone) is often confused with silicon (silicon). A famous example is Silicon Valley, which is actually silicon.
Silicon as a computer chip
When choosing a material for the basis of computer transistors, resistance was a key factor. Conductors have low resistance and conduct current very easily, while insulators block current due to their high resistance. The transistor must combine both properties.
Silicon is not the only semiconductor substance on Earth - it's not even the best semiconductor. However, it is widely available. It is not difficult to mine and easy to work with. And most importantly, scientists have found a reliable way to derive ordered crystals from it. These crystals are to silicon what diamond is to diamond.
The construction of ideal crystals is one of the main aspects of the production of computer chips. These crystals are then sliced into thin wafers, engraved, processed, and go through hundreds of treatments before they become commercial processors. It's possible to make better transistors out of carbon or exotic materials like germanium, but none of them will make it possible to recreate such a large-scale production - at least not yet.
At the moment, silicon crystals are created in 300 mm cylinders, but research is rapidly approaching the 450 mm milestone. This should cut production costs, but keep the growth rate of speed. What's after that? We'll likely finally have to ditch silicon in favor of a more advanced material - good news for progress, but almost certainly bad news for your wallet.
Silicon as extraterrestrial life
The phrase "carbon life" is mentioned quite often, but what does it mean? This means that the basic structural molecules of our body (proteins, amino acids, nucleic acids, fatty acids, etc.) are built on the basis of carbon atoms. This is because carbon can be tetravalent. Oxygen can form two stable chemical bonds at the same time, nitrogen can only form three, but carbon can hold up to four different atoms at once. This is a powerful basis for building molecules and developing life.
Because the periodic table is ordered so that the elements in the vertical column have similar chemical properties - and right below carbon is silicon. This is why so many theorists pay attention to "silicon life", one of the arguments in their favor is the fact that silicon is also tetravalent.
Of course, given that there is much more silicon on Earth than carbon, there must be a good reason why organic life is based on carbon. And here we need to turn again to the periodic table. Elements that are vertically lower have heavier nuclei and larger electron shells, so silicon is less suitable for precision tasks like building DNA because of its size. Thus, in another part of the Universe, the development of an organism based on silicon is theoretically possible, but this is unlikely to happen on our planet.
Silicon will be in the news for a long time to come, because even if some element replaces it as the basis for computer computing, it will take a very long time before the full transition. In addition, there are other areas of its application, and it is possible that new ways of using this substance will be found. In all likelihood, silicon will still remain one of the main substances in the physical world of human activity.
How microchips are made
To understand what is the main difference between these two technologies, it is necessary to brief digression in 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 conduction). A semiconductor is a substance that is superior in conductivity to dielectrics, but inferior to metals. Both types of semiconductors can be based on silicon (Si), which in its pure form (the so-called intrinsic semiconductor) is a poor conductor of electric current, but the addition (incorporation) of a certain impurity into silicon makes it possible to 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 an electronic type of conductivity, while the acceptor impurity leads to the formation of p-type semiconductors with a hole type of conductivity. Contacts of p- and n-semiconductors make it possible to form transistors, the main structural elements of modern microcircuits. Such transistors, called CMOS transistors, can be in two basic states: open, when they conduct electricity, and locked while they do not conduct electricity. Since CMOS transistors are the main elements of modern microcircuits, let's talk about them in more detail.
How a CMOS transistor works
The simplest n-type CMOS transistor has three electrodes: source, gate and drain. The transistor itself is made in 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, depleted layers (layers in which there are no main charge carriers) are formed at the transition boundaries of the p- and n-regions. In the normal state, 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 the source to the 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 of minor charge carriers under the influence of the generated electric fields, 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), then the situation will change radically. Under the influence of the electric field of the gate, holes are pushed deep into the p-semiconductor, and electrons, on the contrary, are drawn into the region 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 the source to the drain. In this case, the transistor conducts current they say that the transistor "opens". If the voltage is removed from the gate, the electrons cease to be drawn into the region between the source and drain, the conductive channel is destroyed and the transistor ceases to pass current, that is, it “locks”. Thus, by changing the voltage at the gate, you can turn on or off the transistor, in the same way as you can turn on or off a conventional toggle switch, controlling the flow of current through the circuit. This is why transistors are sometimes called electronic switches. However, unlike conventional mechanical switches, CMOS transistors have virtually no inertia and are capable of switching from on to off state trillions of times per second! It is this characteristic, that is, the ability to instantly switch, that ultimately determines the speed of the processor, which consists of tens of millions of such simple transistors.
So, a modern integrated circuit consists of tens of millions of the simplest CMOS transistors. Let us dwell in more detail on the manufacturing process of microcircuits, the first stage of which is the preparation of silicon substrates.
Step 1. Growing blanks
The creation of such substrates begins with the growth of a cylindrical silicon single crystal. Subsequently, round plates (wafers) are cut from such single-crystal blanks (blanks), the thickness of which is approximately 1/40 inch, and the diameter is 200 mm (8 inches) or 300 mm (12 inches). This is the silicon substrates used for the production of microcircuits.
When forming wafers from silicon single crystals, the circumstance is taken into account that for ideal crystal structures, the physical properties largely depend on the chosen direction (the anisotropy property). For example, the resistance of a silicon substrate will be different in the longitudinal and transverse directions. Similarly, depending on the orientation of the crystal lattice, the silicon crystal will react differently to any external influences associated with 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 a silicon single crystal blank is either 200 or 300 mm. Moreover, the diameter of 300 mm is relatively new technology, which we will discuss below. It is clear that a plate of such a diameter can accommodate far more than one chip, even if we are talking about an Intel Pentium 4 processor. Indeed, several dozen microcircuits (processors) are formed on one such substrate plate, but for simplicity we will consider only the processes occurring a small area of one future microprocessor.
Step 2. Application of a protective film of dielectric (SiO2)
After the formation of the silicon substrate, the stage of creating the most complex semiconductor structure begins.
To do this, it is necessary to introduce the so-called donor and acceptor impurities into silicon. However, the question arises how to carry out the introduction of impurities according to a precisely given pattern-pattern? To make this possible, those areas where impurities are not required are protected with a special silicon dioxide film, leaving only those areas that are exposed 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 wafer, 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 not contain defects, it is necessary to strictly maintain a constant temperature at all points of the plate during the oxidation process. If not the entire wafer is to be covered with a silicon dioxide film, then a Si3N4 mask is preliminarily applied to the silicon substrate to prevent unwanted oxidation.
Step 3 Apply 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 the so-called photoresist is applied to the surface of the plate. The term "photoresist" refers to light-sensitive and resistant to aggressive factors compositions. The compositions used must, on the one hand, have certain photographic properties (become soluble under the influence of ultraviolet light and be washed out during the etching process), and on the other hand, 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 a photoresist and its further irradiation with ultraviolet according to a given pattern is called photolithography and includes the following main operations: formation of a photoresist layer (substrate treatment, deposition, drying), formation of a protective relief (exposure, development, drying) and image transfer to the substrate (etching, deposition etc.).
Before applying the photoresist layer (Fig. 3) to the substrate, the latter is subjected to pretreatment, as a result of which its adhesion to the photoresist layer is improved. 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. (Speaking of a practically uniform layer, one takes into account the fact that under the action of centrifugal forces the thickness of the formed film increases from the center to the edges, however, this method of applying the photoresist allows one to withstand fluctuations in the layer thickness within ± 10%.)
Step 4. Lithography
After the application and drying of 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 action of ultraviolet radiation falling on certain areas of the photoresist layer, the latter changes the properties of solubility, for example, the illuminated areas cease to dissolve in the solvent, which remove areas of the layer that have not been exposed to illumination, or vice versa - the illuminated areas dissolve. According to the way the relief is formed, photoresists are divided into negative and positive. Negative photoresists under the action of ultraviolet radiation form protective areas of the relief. Positive photoresists, on the contrary, under the influence of ultraviolet radiation acquire the properties of fluidity and are washed out by the solvent. Accordingly, a protective layer is formed in those areas that are not exposed to ultraviolet radiation.
To illuminate the desired areas of the photoresist layer, a special mask template is used. Most often, optical glass plates with opaque elements obtained by a photographic or other method are used for this purpose. In fact, such a template contains a drawing of one of the layers of the future microcircuit (there may be several hundred such layers in total). Because this pattern is a reference, it must be made with great precision. In addition, taking into account the fact that a lot of photoplates will be made using 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 pattern (Fig. 4) illuminates only the desired areas of the surface of the photoresist layer. After irradiation, the photoresist is subjected to development, as a result of which unnecessary parts of the layer are removed. This opens the corresponding part of the layer of silicon dioxide.
Despite the apparent simplicity of the photolithographic process, it is this stage of microchip production that is the most difficult. The fact is that, in accordance with Moore's prediction, the number of transistors on a single chip is growing exponentially (doubling every two years). Such an increase in the number of transistors is possible only 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 - it is not so easy to focus a laser beam to a point. The fact is that, in accordance with the laws of wave optics, the minimum spot size into which the laser beam is focused (in fact, this 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 shortening the wavelength of light. This is what made it possible to reduce the size of the elements integrated circuit. Since the mid-1980s, ultraviolet radiation produced by a laser has been used in photolithography. The idea is simple: the wavelength of ultraviolet radiation is shorter than the wavelength of visible light, therefore it is possible to get finer lines on the surface of the photoresist. Until recently, deep ultraviolet radiation (Deep Ultra Violet, DUV) with a wavelength of 248 nm was used for lithography. However, when photolithography crossed the border of 200 nm, serious problems arose, for the first time calling into question the possibility of further use of this technology. For example, at a wavelength less than 200 µm, too much light is absorbed by the photosensitive layer, so the process of transferring the circuit template to the processor becomes more complicated and slower. Problems like these are driving researchers and manufacturers to look for alternatives to traditional lithographic technology.
The new lithography technology, called EUV lithography (Extreme UltraViolet ultraviolet radiation), is based on the use of ultraviolet radiation with a wavelength of 13 nm.
The transition from DUV to EUV lithography provides more than a 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 current lithographic technology makes it possible to apply a template with a minimum conductor width of 100 nm, while EUV lithography makes it possible to print lines of much smaller widths - 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 about 12 atoms thick.
Step 5 Etching
After the photoresist layer is illuminated, the etching stage begins to remove the silicon dioxide film (Fig. 8).
The pickling process is often associated with acid baths. This method of etching in acid is well known to radio amateurs who made printed circuit boards on their own. To do this, a pattern of tracks of the future board is applied to the foil textolite with a varnish that acts as a protective layer, and then the plate is lowered into a bath with nitric acid. Unnecessary sections of the foil are etched away, exposing a clean textolite. This method has a number of disadvantages, the main of which is the inability to accurately control the layer removal process, since too many factors affect 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 by the photoresist from the side. Therefore, in the production of processors, a dry etching method, also called plasma, is used. This method makes it possible to accurately control 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 form volatile by-products.
After the etching procedure, that is, when the desired areas of pure silicon are exposed, the rest of the photolayer is removed. Thus, a silicon dioxide pattern remains on the silicon substrate.
Step 6. Diffusion (ion implantation)
Recall that the previous process of forming the necessary 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 incorporation of impurities is carried out by means of diffusion (Fig. 9) uniform incorporation of impurity atoms into the crystal lattice of silicon. To obtain an n-type semiconductor, antimony, arsenic or phosphorus are usually used. To obtain a p-type semiconductor, boron, gallium or aluminum is used as an impurity.
Ion implantation is used for the dopant diffusion process. The process of implantation consists in the fact that the ions of the required impurity are “shot out” from the high-voltage accelerator and, having sufficient energy, penetrate 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. An additional thin layer of silicon dioxide is grown to create the next layer in the resulting circuit diagram. After that, a layer of polycrystalline silicon and another layer of photoresist are applied. Ultraviolet radiation is passed through the second mask and highlights the corresponding pattern on the photo layer. Then the stages of photolayer dissolution, etching and ion implantation follow again.
Step 7 Sputtering and Deposition
The imposition of new layers is carried out several times, while “windows” are left for interlayer connections in the layers, which are filled with metal atoms; as a result, metal strips are created on the crystal - conductive regions. Thus, in modern processors, links are established between layers that form a complex three-dimensional scheme. 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 subjected to during the layering process, silicon substrates are initially made thick enough. Therefore, before cutting the plate into individual processors, its thickness is reduced by 33% and dirt is removed from reverse side. Then, a layer of a special material is applied to the back side of the substrate, which improves the fastening of the crystal to the case of the future processor.
Step 8. Final step
At the end of the formation cycle, all processors are thoroughly tested. Then, specific crystals that have already passed the test are cut out from the substrate plate using a special device (Fig. 10).
Each microprocessor is built into a protective housing, which also provides electrical connection of the microprocessor chip with external devices. The package type depends on the type and intended application of the microprocessor.
After being sealed into the housing, each microprocessor is retested. Faulty processors are rejected, and serviceable ones are subjected to stress tests. Then the processors are sorted depending on their behavior under various clock frequencies ah and supply voltages.
Promising technologies
The technological process for the production of microcircuits (in particular, processors) has been considered by us in a very simplified way. But even such a superficial presentation makes it possible to understand the technological difficulties that one has to face 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 norm of the technological process and how, in fact, does the design norm of 130 nm differ from the norm of 180 nm? 130 nm or 180 nm is a characteristic minimum distance between two adjacent elements in one layer of the microcircuit, that is, a kind of grid step to which the microcircuit elements are bound. At the same time, it is quite obvious that the smaller this characteristic size, the more transistors can be placed on the same chip area.
Currently, Intel processors use a 0.13 micron manufacturing process. This technology is used to manufacture the Intel Pentium 4 processor with the Northwood core, the Intel Pentium III processor with the Tualatin core, and the Intel Celeron processor. In the case of using such a technological process, the useful width of the transistor channel is 60 nm, and the thickness of the gate oxide layer does not exceed 1.5 nm. All in all, the Intel Pentium 4 processor contains 55 million transistors.
Along with increasing the density of transistors in a processor chip, the 0.13-micron technology, which replaced the 0.18-micron, has other innovations. First, it uses copper connections between the individual transistors (in 0.18 micron technology, the connections were aluminum). Secondly, 0.13 micron technology provides lower power consumption. For mobile technology, for example, this means that the power consumption of microprocessors becomes less, and the operating time from battery more.
Well, the last innovation that was embodied in the transition to a 0.13-micron technological process is the use of silicon wafers (wafer) with a diameter of 300 mm. Recall that before that, most processors and microcircuits were manufactured on the basis of 200 mm wafers.
Increasing the wafer diameter reduces the cost of each processor and increases 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, respectively, and the number of processors obtained from one wafer with a diameter of 300 mm is more than twice as large.
In 2003, the introduction of a new technological process with an even lower design standard, namely 90-nanometer, is expected. The new process technology that Intel will manufacture most of its products, including processors, chipsets and communications equipment, was developed at Intel's 300mm wafer pilot plant D1C in Hillsboro, Oregon.
On October 23, 2002, Intel Corporation announced the opening of a new $2 billion facility in Rio Rancho, New Mexico. The new plant, named F11X, will use modern technology, according to which processors on 300 mm substrates will be produced using a technological process 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 manufacturing facility at Fab 24 in Leixlip, Ireland, which is designed to fabricate semiconductor components on 300mm silicon wafers with a 90nm design rule. The 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. feet is expected to be operational in the first half of 2004 and will employ more than a thousand people. The cost of the object is about 2 billion dollars.
The 90nm process uses a number of advanced technologies. These include the world's smallest mass-produced CMOS transistors with a gate length of 50 nm (Figure 11), which provides increased performance while reducing power consumption, and the thinnest gate oxide layer of any transistor ever manufactured only 1.2 nm (Figure 12), or less than 5 atomic layers, and the industry's first implementation of high performance stressed silicon technology.
Of the listed characteristics, perhaps only the concept of “stressed silicon” needs to be commented on (Fig. 13). In such silicon, the distance between atoms is greater than in a conventional semiconductor. This, in turn, allows the current to flow more freely, similar to how vehicles with wider lanes move more freely and faster.
As a result of all innovations, the performance of transistors is improved by 10-20%, while increasing production costs by only 2%.
In addition, the 90nm process uses seven layers per chip (Figure 14), one more layer than the 130nm process, and copper connections.
All of these features combined with 300mm silicon wafers provide Intel with performance, volume and cost advantages. Consumers benefit as well, as Intel's new process technology allows the industry to continue to evolve in accordance with Moore's Law, improving processor performance time and time again.
CPU it is the heart of any modern computer. Any microprocessor is essentially a large integrated circuit on which transistors are located. By passing an electric current, transistors allow you to create binary logic (on - off) calculations. Modern processors are based on 45 nm technology. 45nm (nanometer) is the size of a single transistor on a processor wafer. Until recently, 90 nm technology was mainly used.
The plates are made of silicon, which is the 2nd largest deposit in the earth's crust.
Silicon is obtained by chemical treatment, purifying it from impurities. After that, it begins to be smelted, forming a silicon cylinder with a diameter of 300 millimeters. This cylinder is further cut into plates with a diamond wire. The thickness of each plate is about 1 mm. In order for the plate to have an ideal surface, after cutting with a thread, it is polished with a special grinder.
After that, the surface of the silicon wafer is perfectly smooth. By the way, many manufacturing companies have already announced the possibility of working with 450 mm plates. The larger the surface - the greater the number of transistors to accommodate, and the higher the performance of the processor.
CPU consists of a silicon wafer, on the surface of which there are up to nine levels of transistors, separated by layers of oxide, for isolation.
Development of processor manufacturing technology
Gordon Moore, one of the founders of Intel, one of the leaders in the production of processors in the world, in 1965, based on his observations, discovered the law according to which new models of processors and microcircuits appeared at regular intervals. The growth in the number of transistors in processors is growing by about 2 times in 2 years. For 40 years now, Gordon Moore's law has been working without distortion. The development of future technologies is not far off - there are already working prototypes based on 32nm and 22nm processor manufacturing technologies. Until the middle of 2004, the processor power depended primarily on the processor frequency, but starting from 2005, the processor frequency practically stopped growing. There is a new multi-core processor technology. That is, several processor cores are created with an equal clock frequency, and during operation, the power of the cores is summed up. This increases the overall power of the processor.
Below you can watch a video about the production of processors.
Almost everyone knows that in a computer, the main element among all the “iron” components is the central processing unit. But the circle of people who imagine how the processor works is very limited. Most users have no idea about this. And even when the system suddenly starts to "slow down", many people think that this processor is not working well, and do not attach importance to other factors. To fully understand the situation, consider some aspects of the CPU.
What is a central processing unit?
What is a processor made of?
If we talk about how an Intel processor or its competitor AMD works, you need to look at how these chips are arranged. The first microprocessor (by the way, it was from Intel, model 4040) appeared back in 1971. It could perform only the simplest operations of addition and subtraction with only 4 bits of information, i.e. it had a 4-bit architecture.
Modern processors, like the first-born, are based on transistors and have much greater speed. They are made by the method of photolithography from a certain number of individual silicon plates that make up a single crystal, into which transistors are imprinted, as it were. The scheme is created on a special accelerator with dispersed boron ions. In the internal structure of processors, the main components are cores, buses, and functional particles called revisions.
Main characteristics
Like any other device, the processor is characterized by certain parameters, which, when answering the question of how the processor works, cannot be ignored. First of all it is:
- Number of Cores;
- number of threads;
- cache size (internal memory);
- clock frequency;
- bus speed.
For now, let's focus on clock speed. No wonder the processor is called the heart of the computer. Like the heart, it works in pulsation mode with a certain number of cycles per second. Clock frequency is measured in MHz or GHz. The higher it is, the more operations the device can perform.
At what frequency the processor operates, you can find out from its declared characteristics or look at the information in But during the processing of commands, the frequency can change, and during overclocking (overlocking) it can increase to extreme limits. Thus, the declared is just an average indicator.
The number of cores is an indicator that determines the number of computing centers of the processor (not to be confused with threads - the number of cores and threads may not match). Due to this distribution, it becomes possible to redirect operations to other cores, thereby increasing overall performance.
How the processor works: instruction processing
Now a little about the structure of executable commands. If you look at how the processor works, you need to clearly understand that any instruction has two components - an operational and an operand.
The operating part indicates what the computer system should do at the moment, the operand determines what the processor should work on. In addition, the processor core can contain two computing centers (containers, threads), which divide the execution of the command into several stages:
- production;
- decryption;
- command execution;
- accessing the memory of the processor itself
- saving the result.
Today, separate caching is used in the form of using two levels of cache memory, which makes it possible to avoid interception by two or more commands of accessing one of the memory blocks.
Processors according to the type of instruction processing are divided into linear (execution of instructions in the order in which they are written), cyclic and branching (execution of instructions after processing branch conditions).
Operations in progress
Among the main functions assigned to the processor, in the sense of executable commands or instructions, there are three main tasks:
- mathematical operations based on the arithmetic-logical device;
- moving data (information) from one type of memory to another;
- making a decision on the execution of the command, and on its basis - the choice of switching to the execution of other sets of commands.
Interaction with memory (ROM and RAM)
In this process, components such as the bus and the read/write channel that are connected to the storage devices should be noted. ROM contains a permanent set of bytes. First, the address bus requests a specific byte from the ROM, then transfers it to the data bus, after which the read channel changes its state and the ROM provides the requested byte.
But processors can not only read data from random access memory but also write them down. In this case, the write channel is used. But, if you look, by and large modern computers purely theoretically, they could do without RAM at all, since modern microcontrollers are able to place the necessary data bytes directly in the memory of the processor chip itself. But you can't do without ROM.
Among other things, the system starts from the hardware test mode (BIOS command), and only then control is transferred to the bootable operating system.
How to check if the processor is working?
Now let's look at some aspects of checking the health of the processor. It must be clearly understood that if the processor was not working, the computer would not be able to start downloading at all.
Another thing is when you want to look at the indicator of the use of the processor's capabilities at a certain moment. This can be done from the standard "Task Manager" (in front of any process, it is indicated how many percent of the processor load it gives). To visually determine this parameter, you can use the performance tab, where changes are tracked in real time. Advanced options can be seen with special programs e.g. CPU-Z.
In addition, you can use multiple processor cores using (msconfig) and Extra options downloads.
Possible problems
Finally, a few words about problems. Here, many users often ask, they say, why does the processor work, but the monitor does not turn on? TO CPU this situation is irrelevant. The fact is that when you turn on any computer, it first tests graphics adapter and then everything else. Perhaps the problem is just in the processor graphics chip(all modern video accelerators have their own graphics processors).
But using the example of the functioning of the human body, one must understand that in the event of a cardiac arrest, the entire body dies. So it is with computers. The processor does not work - the entire computer system “dies”.
The roots of our digital lifestyle certainly stem from semiconductors, which have enabled the creation of sophisticated transistor-based computing chips. They store and process data, which is the basis of modern microprocessors. Semiconductors, which today are made from sand, are a key component of almost any electronic device, from computers to laptops and cell phones. Even cars now cannot do without semiconductors and electronics, as semiconductors control the air conditioning system, fuel injection process, ignition, sunroof, mirrors and even steering (BMW Active Steering). Today, almost any device that consumes energy is built on semiconductors.
Microprocessors are without a doubt among the most complex semiconductor products, as the number of transistors will soon reach a billion, and the range of functionality is already amazing today. Dual core coming soon Core processors 2 on an almost finished 45nm Intel process, and they will already contain 410 million transistors (although most of them will be used for the 6MB L2 cache). The 45nm process is named after the size of a single transistor, which is now about 1,000 times smaller than the diameter of a human hair. To a certain extent, this is why electronics begins to rule everything in our lives: even when the size of the transistor was larger, it was very cheap to produce not very complex microcircuits, the budget of transistors was quite large.
In this article, we will look at the fundamentals of microprocessor manufacturing, but also touch on the history of processors, architecture, and look at different products on the market. You can find many on the Internet interesting information, some of which are listed below.
- Wikipedia: Microprocessor. This article reviewed different types processors and provides links to manufacturers and additional wiki pages about processors.
- Wikipedia: Microprocessors (Category). See the microprocessor section for even more links and information.
PC Competitors: AMD and Intel
Founded in 1969, Advanced Micro Devices Inc. is headquartered in Sunnyvale, California, while the heart of Intel, which was founded just a year earlier, is a few miles away in Santa Clara. AMD today has two factories: in Austin (Texas, USA) and in Dresden (Germany). The new plant will be up and running soon. In addition, AMD has joined forces with IBM in the development of processor technology and manufacturing. Of course, all of this is just a fraction of the size of Intel, as the market leader today has almost 20 factories in nine locations. Approximately half of them are used for the production of microprocessors. So when you compare AMD and Intel, remember that you are comparing David and Goliath.
Intel has an undeniable advantage in the form of huge production capacity. Yes, the company today is a leader in the implementation of advanced technological processes. Intel is about a year ahead of AMD in this regard. As a result, Intel can use in its processors more transistors and more cache. AMD, unlike Intel, has to optimize the technical process as efficiently as possible in order to keep up with the competitor and release decent processors. Of course, the design of processors and their architecture are very different, but the technical process of production is built on the same basic principles. Although, of course, there are many differences in it.
Microprocessor manufacturing
The production of microprocessors consists of two important stages. The first is in the production of the substrate, which AMD and Intel do in their factories. This includes imparting conductive properties to the substrate. The second stage is the test of substrates, assembly and packaging of the processor. The last operation is usually performed in less expensive countries. If you look at Intel processors, you will find that the packaging was made in Costa Rica, Malaysia, the Philippines, etc.
AMD and Intel are now trying to produce products for the maximum number of market segments, moreover, based on the minimum possible assortment of crystals. A great example is the line of processors Intel Core 2 duos. There are three processors here, codenamed for different markets: Merom for mobile applications, Conroe - desktop version, Woodcrest - server version. All three processors are built on the same technological basis, which allows the manufacturer to make decisions at the last stages of production. Features can be enabled or disabled, and the current clock rate gives Intel an excellent chip yield rate. If there is an increase in market demand for mobile processors, Intel may focus on Socket 479 models. If the demand for desktop models increases, the company will test, validate and package dies for Socket 775, while server processors are packaged for Socket 771. Even quad-core processors are created this way: two dual-core dies are installed in one package, so we get four cores.
How chips are made
The production of chips consists in the imposition of thin layers with a complex "pattern" on silicon substrates. First, an insulating layer is created that acts as an electrical shutter. A photoresist material is then applied on top, and unwanted areas are removed using masks and high-intensity irradiation. When the irradiated areas are removed, areas of silicon dioxide will open underneath, which is removed by etching. After that, the photoresistive material is also removed, and we get a certain structure on the silicon surface. Then held additional processes photolithography, with different materials, until the desired 3D structure is obtained. Each layer can be doped with a certain substance or ions, changing the electrical properties. Windows are created in each layer in order to then bring metal connections.
As for the production of substrates, they must be cut from a single single-crystal-cylinder into thin "pancakes" in order to be easily cut into separate processor crystals later. Sophisticated testing is carried out at every step of production to assess the quality. Electrical probes are used to test each chip on the substrate. Finally, the substrate is cut into individual cores, non-working cores are immediately eliminated. Depending on the characteristics, the core becomes one or another processor and is enclosed in a package that facilitates the installation of the processor on motherboard. All functional blocks go through intensive stress tests.
It all starts with pads
The first step in processor manufacturing is done in a clean room. By the way, it is important to note that such a technological production is an accumulation of huge capital per square meter. The construction of a modern plant with all the equipment easily "flies away" 2-3 billion dollars, and it takes several months to test runs of new technologies. Only then can the plant mass-produce processors.
In general, the chip manufacturing process consists of several substrate processing steps. This includes the creation of the substrates themselves, which will eventually be cut into individual crystals.
It all starts with growing a single crystal, for which the seed crystal is embedded in a bath of molten silicon, which is located just above the melting point of polycrystalline silicon. It is important that the crystals grow slowly (about a day) to ensure that the atoms are arranged correctly. Polycrystalline or amorphous silicon is made up of many assorted crystals that will result in unwanted surface structures with poor electrical properties. Once the silicon is melted, it can be doped with other substances that change its electrical properties. The whole process takes place in a sealed room with a special air composition so that the silicon does not oxidize.
The single crystal is cut into "pancakes" using a circular diamond saw, which is very accurate and does not create large irregularities on the surface of the substrates. Of course, in this case, the surface of the substrates is still not perfectly flat, so additional operations are needed.
First, using rotating steel plates and an abrasive material (such as aluminum oxide), a thick layer is removed from the substrates (a process called lapping). As a result, irregularities ranging in size from 0.05 mm to approximately 0.002 mm (2,000 nm) are eliminated. The edges of each substrate should then be rounded off, as sharp edges can cause the layers to peel off. Next, the etching process is used, when using various chemicals (hydrofluoric acid, acetic acid, nitric acid) the surface is smoothed by about 50 microns. There is no physical deterioration of the surface as the whole process is completely chemical. It allows you to remove the remaining errors in the crystal structure, as a result of which the surface will be close to ideal.
The last step is polishing, which smoothes the surface down to roughness, maximum 3 nm. Polishing is done with a mixture of sodium hydroxide and granular silica.
Today, microprocessor wafers are 200 or 300 mm in diameter, allowing chip makers to get many processors from each wafer. The next step will be 450 mm substrates, but before 2013 they should not be expected. In general, the larger the substrate diameter, the more chips of the same size can be produced. A 300 mm substrate, for example, gives more than twice more processors than 200 mm.
We have already mentioned doping, which is carried out during the growth of a single crystal. But doping is carried out both with the finished substrate and during photolithography processes later. This allows you to change the electrical properties of certain areas and layers, and not the entire structure of the crystal.
The addition of a dopant may occur via diffusion. Dopant atoms fill the free space inside the crystal lattice, between silicon structures. In some cases, the existing structure can also be doped. Diffusion is carried out with the help of gases (nitrogen and argon) or with the help of solids or other sources of dopant.
Another approach to doping is ion implantation, which is very useful in changing the properties of a substrate that has been doped, since ion implantation is carried out at ordinary temperature. Therefore, existing impurities do not diffuse. A mask can be applied to the substrate, which allows you to process only certain areas. Of course, one can talk about ion implantation for a long time and discuss the penetration depth, additive activation at high temperature, channel effects, penetration into oxide levels, etc., but this is beyond the scope of our article. The procedure can be repeated several times during production.
To create sections of an integrated circuit, the process of photolithography is used. Since in this case it is not necessary to irradiate the entire surface of the substrate, it is important to use the so-called masks, which transmit high-intensity radiation only to certain areas. Masks can be compared to a black and white negative. Integrated circuits have many layers (20 or more), and each of them requires its own mask.
A thin chrome film structure is applied to the surface of a quartz glass plate to create a template. At the same time, expensive tools using an electron beam or a laser write the necessary data of an integrated circuit, as a result of which we get a pattern of chromium on the surface of a quartz substrate. It is important to understand that each modification of the integrated circuit leads to the need to produce new masks, so the whole process of making changes is very costly. For very complex schemes masks are created for a very long time.
Using photolithography, a structure is formed on a silicon substrate. The process is repeated several times until many layers (more than 20) are created. Layers can consist of different materials, moreover, you also need to think through the connections with microscopic wires. All layers can be alloyed.
Before the photolithography process begins, the substrate is cleaned and heated to remove sticky particles and water. The substrate is then coated with silicon dioxide using a special device. Next, a bonding agent is applied to the substrate, which ensures that the photoresist material that will be applied in the next step remains on the substrate. The photoresist material is applied to the middle of the substrate, which then begins to rotate at high speed so that the layer is evenly distributed over the entire surface of the substrate. The substrate is then heated again.
The cover is then irradiated through the mask with a quantum laser, hard ultraviolet radiation, X-rays, electron beams or ion beams - all of these sources of light or energy can be used. Electron beams are mainly used for masks, X-rays and ion beams for research purposes, and industrial production today is dominated by hard UV radiation and gas lasers.
Hard UV radiation at a wavelength of 13.5 nm irradiates the photoresist material as it passes through the mask.
Projection time and focus are very important to obtain the desired result. Poor focusing will result in extra particles of photoresist material remaining, as some holes in the mask will not be irradiated properly. The same will happen if the projection time is too short. Then the photoresist structure will be too wide, the areas under the holes will be underexposed. On the other hand, excessive projection time creates too large areas under the holes and too narrow a photoresist structure. As a rule, it is very time-consuming and difficult to adjust and optimize the process. Unsuccessful adjustment will lead to serious deviations in the connecting conductors.
A special stepping projection unit moves the substrate to the desired position. Then a line or one section can be projected, most often corresponding to one processor chip. Additional micro settings may make additional changes. They can debug existing technology and optimize the process. Micro-installations usually work on areas less than 1 sq. mm, while conventional installations cover larger areas.
The substrate then proceeds to a new stage where the weakened photoresist material is removed, allowing access to the silicon dioxide. There are wet and dry etch processes that treat areas of silicon dioxide. Wet processes use chemical compounds, while dry processes use gas. A separate process is to remove the remnants of the photoresist material. Manufacturers often combine wet and dry removal so that the photoresist material is completely removed. This is important because the photoresist material is organic and, if left unremoved, can cause defects in the substrate. After etching and cleaning, you can proceed to the inspection of the substrate, which usually happens on each milestone, or transfer the substrate to a new cycle of photolithography.
Substrate test, assembly, packaging
Finished substrates are tested on the so-called probe control units. They work with the entire substrate. Probe contacts are superimposed on the contacts of each crystal, allowing electrical tests to be carried out. The software tests all the functions of each core.
By cutting from the substrate, individual nuclei can be obtained. At the moment, the probe control installations have already identified which crystals contain errors, so after cutting they can be separated from the good ones. Previously, damaged crystals were physically marked, now this is not necessary, all information is stored in a single database.
Crystal mount
The functional core then needs to be bonded to the processor package using adhesive material.
Then you need to make wire connections connecting the contacts or legs of the package and the crystal itself. Gold, aluminum or copper connections can be used.
Most modern processors use plastic packaging with a heat spreader.
Typically, the core is encased in ceramic or plastic packaging to prevent damage. Modern processors are equipped with a so-called heat spreader, which provides additional protection for the crystal, as well as a large contact surface with the cooler.
Processor testing
The last stage involves testing the processor, which occurs at elevated temperatures, in accordance with the specifications of the processor. The processor is automatically installed in test socket, after which all the necessary functions are analyzed.
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