microchips/silicone printing

[Tydfil]

hi all, hope you are well.

 

i have a question, i gen do not know the answer to thought id start here.

 

why are microchips/processors etc printed on circular plates instead of square ones?

 

surely they can get more onto a square or rectangular plate, lots of wasted space on a circle it seems.

 

thanks

[7heo]

Why are Silicon Wafers Round?

 

TL;DR:

Quote

Silicon wafers are made from a spinning mechanism. Wafers are thin cuts from a single silicon crystal that is formed with [from] an ingot is dipped into a liquid silicon “soup” and pulled out. For the single crystal to be made, the ingot is spun as it is pulled out, and the centrifugal force attracts and locks in the silicon molecules.

Note: emphasis/corrections mine.

 

Additional notes: silicon is the second most abundant element on this planet. Even if the specific grade of silicon needed for semiconductors (EGS - or Electronics Grade Silicon) makes this a lot less simple than "just using the second most abundant element", it still is negligible compared to the energy and precision requirements involved in the rest of the steps of making semiconductors. So that little silicon waste is totally acceptable, and contributes to keeping costs down.

[AbydosOne]

1 minute ago, Tydfil said:

why are microchips/processors etc printed on circular plates instead of square ones?

Silicon (not silicone) wafers are cut from a silicon boule, which is produced somewhat like how you make a dipped candle. They're not square basically because it would make it harder to uniformly create the boule.

[mariushm]

It's how the wafers are made.  Pure silicon and gravity results in basically a candle like piece of material which then has its exterior polished and then wafer (discs) are cut from the material. See video below.

 

Then the machines that make chips (etching, deposition, masking etc) use very narrow light beams and ultra violet and lens and other optical equipment that works best with things that are round (same distance from the center towards the edges)...  Some process steps involve applying chemical solutions over the surface and using centrifugal forces to spread the liquid evenly across the disc, and these wouldn't work as well with square or other shapes...

The more you go towards the edges the more defects you get due to optics and other issues. It's complicated and hard to explain. ..

 

Search Youtube for  how processors / chips are made and you'll find videos showing the steps.