question about Silicon Wafers / Die Shots we usually see

[Borealis7]

just a silly question...why are they round?

i mean...if the CPU dies are all square/rectangular then wouldn't it make more sense to have rectangular wafers? on the edges you can see "parts" of dies that would probably go to waste.

assuming a side length of x, a square wafer would have x^2 space while a circular one only has Pi(x/2)^2 and so x^2(1-pi/4) ~ 21% less space

 

[StrangerGuy]

Due to the ingot growing process, the pure silicon ingot that is used as the starting material for the wafers needs to be round.

 

[alyarb]

http://en.wikipedia.org/wiki/Czochralski_process

not exactly the most edited wiki page but there's some info there.

 

[WhoBeDaPlaya]

Sliced from ingots. Plus they usually have a handle flat to indicate the crystal planes.

 

[aigomorla]

By AMD
http://www.youtube.com/watch?v=-GQmtITMdas

i dont think they own those fabs anymore do they?

 

[JFAMD]

Part of the process also includes spinning the wafer. That works a lot easier when it is round.