Eli5- How are incredibly small hardware piece built?
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The standard method is called photolithography and basically works by selectively removing stuff:
1. Put a layer of your building material on a surface. The goal is now to remove the parts you don’t want with some acid.
2. Put a layer of a special material on top that can resist the acid, but can be destroyed by light or altered in a way such that it isn’t resistant to the acid anymore.
3. Shine a laser on the parts you don’t want to keep – this is the essential step that allows us to create fine structures since we can focus a laser much finer than we can apply some material.
4. Now put the acid onto the whole surface – parts that were touched by the laser light in step 3 are etched away, the others remain.
5. Now remove the coating layer that remains (from step 2) with some chemical that doesn’t attack the building material from step 1.
Then you end up with very fine structures on top of some bulk. You can also repeat this for additional layers (though usually you don’t stack too many since the surface is no longer flat, so precision gets worse.
Now, there are variations of this technique (for example, you might use a material in 3. that becomes resistant to acid after shining light on it and such), but this is the main idea. Of course, it’s not easy at all to get the right amount of stuff, focus the lasers (and move them correctly) and so on. Usually, there’s also an additional chemical step required between 3 and 4 because the laser light only alters the coating layer and you still need to remove it.
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