fab related question

[raghunaandan]

why the silicon substrae wafer is manufactured in only circle shape ? I was asked this question in interview ? could anyone help me in finding answer? :drevil: :drevil: :roll:

 

[dick_freebird]

Cylindrical boule is the most stress-free and sort of natural.
It would be very difficult to convince silicon to pull in a
square, triangular, ... cross section. And doing so across
the huge thermal range from melt to room temp would
surely add a whole mess of crystal stress / strain /
dislocations. When you want pefect purity and order
you let the crystal grower do it their way, because what
you think is cute has no help for that.

You will find 2D (ribbon) growth out there but this is well
later than the industry's formative period, where you took
what you could get (which has always been round, from
the 1" wafer days until now).