How Are Transistors Positioned on Computer Chips?

[Demystifier]

I sort of understand how a computer chip works and what is its architecture. But how is it made? I mean, a chip contains billions of transistors, each having a microscopic size. Each transistor must be put at a very precise place. How do they control the position of a single tiny transistor? And how do they do it for such a big number of them?

A link with an elementary explanation of this would also be welcome.

 

[Jonathan Scott]

This might help:
http://www.madehow.com/Volume-2/Integrated-Circuit.html

 

[Demystifier]

This might help:
http://www.madehow.com/Volume-2/Integrated-Circuit.html

If I understood it correctly, the image of the whole architecture is encoded into the mask. But if so, then my question reduces to the following one: How is the mask made?

 

[Jonathan Scott]

It's drawn using computer-aided drawing tools at a much larger scale then reduced optically.
Edit: The circuit is built up in layers, and each mask describes a single layer.

 

[Demystifier]

Great, I think I understand it now!

 

[nsaspook]

After all that work the first good ones are framed.

and the bad ones are made into keychains.
http://www.chipsetc.com/intel-keychains-page-3.html

 

[berkeman]

After all that work the first good ones are framed

98% yield -- nice!

 

[CWatters]

One of my first jobs in the 1980's was drawing the mask for a chip by hand. Each mask used 4 sheets of A0 drawing paper joined together and was drawn with a coloured pencil. The drawing was then digitised and fed to a machine that looked like a very large flat bed plotter. Instead of a pen it carried a knife blade that cut through the top layer of a two ply sheet of plastic film. The top layer was red and the bottom clear. A room small full of people were employed to peel off the top layer of red film leaving transparent tracks. The resulting sheet was then photographically reduced to produce the mask used in production. Very time consuming.

 

[dlgoff]

A little old video, but from someone who knows; Fairchild.

 

[nsaspook]

A little old video, but from someone who knows; Fairchild.

That's a great old video but junction diffusion has been replaced in many steps by ion implantation because of the level of doping precision needed in modern devices.

 

[dlgoff]

... junction diffusion has been replaced in many steps by ion implantation ...

I want one of those $5x10⁶ machines to replace my little set-up.

 

[nsaspook]

I want one of those $5x10⁶ machines to replace my little set-up.

We still have one (vacuum evaporator) that's used for sputter coating non-conductive specimens for electron microscope inspection.