: How are manufacturers able to manufacture really small cpu transistors?
In: Technology
The process is called photolithography. Using a mask to create a pattern on a chip, UV light is shone and focused with a lens to make a tiny pattern. The material that is exposed to the light can then be more easily removed.
You know how you can use a magnifying glass to burn stuff by concentrating rays in a tiny area?
Manufacturers use a magnifying glass with a pattern on it, then the concentrated rays burn out very tiny patterns in a tiny area. The burnt areas have different physical properties to unburnt areas, and with the right pattern this creates a transistor.
Photolithography. You know how a projector can take a small image and turn it into a massive projected image? You basically do that in reverse, large designs which get focused down and etched into the silicon by bombarding it with light.
Lithography is the term your seeing over and over here. But it’s not as simple as everyone is making it sound, it’s a really amazing process to generate appropriately small wavelengths of light.
Eli5 version is, imagine light is like a marker, you can only make lines as thin as your marker tip, in order to make a smaller marker tip they use one marker (a laser) to make a new marker that’s smaller, by shooting a laser into a perfectly round ball of tin, that tin then emits new light if a smaller wavelength (aka smaller marker)
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This is a very complicated question since modern processors take like 3 months and over 1000 steps to make, but ill do my best to skip all the detail and make it really ELI5
They use special chemicals and light to draw a pattern, or mask, on the silicon. They can then modify or remove the parts of the silicon that is not exposed. This process along with several other specialized processes for each step is repeated to modify the silicon to make transistors, replace parts of it with wiring to connect everything and then build a big stack of wiring on top of it that connects it all to the rest of the computer.
They key processes used are:
Lithography (drawing a pattern with light and chemicals)
Implant (modifying exposed silicon by adding trace amounts of other atoms to it)
Etch (removing exposed silicon (or other materials) by either chemical solutions or chemical plasmas)
Deposition (depositing a film on the silicon, sometimes to fill in silicon that was removed with etch, sometimes to make a new film that will be etched to have something else filled into it)
Polish (smoothing out the wafer after various steps make it rough or deposit too much material)
They use chemicals to build a thin layer, use light to burn it off in places, then more chemicals to actually modify the exposed parts of the chip (e.g. acids to create channels for conductors).
The advantage of using light is you can shine it through a bigger guide (that creates the necessary patterns) and reflect it down to a very small size.
Take a look at a manufacturing process flow [like the following](https://en.wikipedia.org/wiki/File:Photolithography_etching_process.svg). This is an incredibly simplified representation of how a transistor is created/embedded within a single solid chunk of silicon. In real modern chips there are hundreds and hundreds of steps.
The first key ingredient is that there are certain chemicals whose properties change dramatically when exposed to light. Specifically we use chemicals that become “harder” when exposed to light (or you can accomplish the same thing with something that becomes “weaker”, it doesn’t matter). By “harder” we mean when this chemical is exposed to light it is far more resistant to being etched away by things like acid.
The second key ingredient is the ability to chemically either etch away solid material (like silicon) or to grow more (deposition) by exposure to a gas of the right chemicals. So you can “acid” etch away and “grow” deposit more by exposing your silicon wafer to a gas.
But how does that allow you to create an incredibly complex embedded circuit of literally [billions of transistors?](https://en.wikipedia.org/wiki/File:Diopsis.jpg). Well you combine the two in a process called photolithography.
First you apply a thin layer of “resist” chemical to the entire silicon wafer and then you exploit its special property by applying light through a kind of stencil called a [photomask](https://www.photo-sciences.com/wp-content/uploads/2018/06/1X-Master-primary-test-dice.jpg). By using this stencil you project a pattern of light onto the chip with light only landing in some place and not in others. Because of the special properties of the “resist” this means that some places become immune to etching and others don’t in the precise shape you applied. Then when you apply your “acid” etch you remove silicon material only according to your complex intended shape because places where the “resist” wasn’t removable (i.e. wasn’t exposed to light) it remains and protects the silicon from this exposure. A similar approach is applied when you need to add material.
So using these three approaches you can remove and add material according to a complex nano-sized floor plan by applying resist and selectively exposing it to light according to a certain pattern. Like, say, [this](http://2.bp.blogspot.com/-j8Z2sbXgETw/VUBNda3YYwI/AAAAAAAAAYM/QXGtUYx5meY/w1200-h630-p-k-no-nu/ProcessFlow2.png) to build up your transistors.
NOTE: It’s a common confusion to think that these hundreds of lithography steps must be applied PER transistor (so there would be hundreds of billions of steps), this isn’t how it works, rather all transistors in the complex network are laid out in a single mask simultaneously and all have their “step 1”, for example, done in the same “apply resist, apply photo-pattern, remove resist then etch or deposit” step.
The real answer for us without special engineering understanding, magic. We live in a time with magic. The magicians make our lives amazing yet there are people who contribute nothing to humanity or even their small community complain. They leave shopping carts in parking spots instead of returning them.
Photolithography is the name of the tech, they use special photo sensitive materials, they lay down different types of silicon then cover in a ‘mask’ they then expose the mask. They have a big light, and a template (like the pattern drawn on a large scale) then focused down to the small scale needed. Then the bits that get exposed are washed off and then an acid is used to dissolve the silicon away. They can then deposit more layers of materials up and up. It’s a very powerful process
I’m 5 and I don’t understand a single answer. What’s a polymer, what do what’s photosensitive etc. 😏
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