How Are CPUs Actually Made?

die shot of processorsphotographs / Shutterstock

The operation of the processors may seem magical, but it is the result of decades of intelligent engineering. As the transistors – constituent elements of any electronic chip – are reduced to microscopic scales, their mode of production becomes more and more complicated.

Photolithography

overhead projectorJ. Robert Williams / Shutterstock

Transistors are now so small that manufacturers can not build them with the usual methods. While the precision turns and even 3D printers Creations can be incredibly complex. They typically reach a micrometer accuracy level (about half a thousandth of an inch) and are not suitable for the nanoscale scales at which chips are manufactured today.

Photolithography solves this problem by eliminating the need to move complicated machines very precisely. Instead, it uses light to burn an image on the chip – like a vintage overhead projector that you might find in classrooms, but conversely, reducing the stencil to the desired precision.

The image is projected onto a silicon wafer, which is machined with very high precision in controlled laboratories, because any trace of dust on the wafer could cause you to lose thousands of dollars. The wafer is covered with a material called photosensitive resin, which reacts with light and is washed away, leaving an etching of the CPU that can be filled with copper or copper. dope to form transistors. This process is then repeated many times, building the processor a bit like a 3D printer accumulate layers of plastic.

The problems of photolithography at the nanoscale

defect diagram of the silicon wafer

Regardless of whether you can reduce the size of the transistors if they do not work, the nanoscale technology faces many problems with physics. Transistors are supposed to stop the electric current when they are off, but they become so small that electrons can pass through them. This is called quantum tunneling and is a massive problem for silicon engineers.

Defects are another problem. Even photolithography has a limit of precision. This is analogous to a blurry image of the projector; it's not so obvious when you blow them up or reduce them. Currently, foundries are trying to mitigate this effect by using Ultraviolet "extreme", a much longer wavelength than humans can perceive, using lasers in a vacuum chamber. But the problem will persist as the size decreases.

Faults can sometimes be mitigated by a process called "binning". If the fault affects a processor core, the processor core is disabled and the chip is sold as the lower part. In fact, most processor alignments are made using the same model, but the cores are disabled and sold at a lower price. If the fault affects the cache or other essential component, it is possible that this chip is ejected, resulting in a lower yield and higher prices. New process nodes, like 7nm and 10nm, will have higher default rates and will therefore be more expensive.

RELATED: What do "7nm" and "10nm" mean for processors and why are they important?

L & # 39; packaging

CPU divided into different partsMchlSkhrv / Shutterstock

Packing the processor for mainstream use is not limited to putting it in a box with styrofoam. When a processor is finished, it is still useless if it can not connect to the rest of the system. The "packaging" process refers to the method where the silicon chip is attached to the circuit board that most people regard as the "CPU".

This process requires a lot of precision, but not as much as the previous steps. The processor chip is mounted on a silicon board and the electrical connections are connected to all the pins that come into contact with the motherboard. Modern processors can have thousands of pins, the upscale AMD Threadripper by having 4094.

Since the processor produces a lot of heat and must also be protected from the front, an "integrated heat spreader" is mounted upward. This makes contact with the matrix and transfers heat to a top-mounted cooler. For some enthusiasts, the thermal paste used to establish this connection is not sufficient, which leads to delidding their processors apply a more premium solution.

Once assembled, it can be packed in real boxes, ready to be put on the shelves and placed in your future computer. With the complexity of manufacturing, most processors cost only a few hundred dollars.

If you want to know more about the process of manufacturing the processors, see the explanations of Wikichip on lithography processes and microarchitectures.

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