Can someone tell me why semiconductor wafers are circular?

Question

trying to understand why they are circular if you end up wasting the circuits on the edges? Thanks.

Answer 1

There are several reasons, one being manufacturing. Wasting silicon is not really a big deal. They actually end up sending all the excess silicon (the part at the edges) back to be recycled, just like cookie dough. You cut out the parts that you're going to use, and you put the rest back to reuse.

Having a round wafer makes it easier for the manufacturing machinery to handle.

Messing up the wafer is very costly, and having sharp edges also increases the likelihood for damage.

Answer 2

The first step in semiconductor manufacturing begins with production of a wafer--a thin, round slice of a semiconductor material, usually silicon.

In this process, purified polycrystalline silicon, created from sand, is heated to a molten liquid. A small piece of solid silicon (seed) is placed on the molten liquid, and as the seed is slowly pulled from the melt the liquid cools to form a single crystal ingot. The surface tension between the seed and molten silicon causes a small amount of the liquid to rise with the seed and cool.

The crystal ingot is then ground to a uniform diameter and a diamond saw blade cuts the ingot into thin wafers.

The wafer is processed through a series of machines, where it is ground smooth and chemically polished to a mirror-like luster.

The wafers are then ready to be sent to the wafer fabrication area where they are used as the starting material for manufacturing integrated circuits.

Source:
http://rel.intersil.com/docs/lexicon/manufacture.html

Answer 3

In addition to the way it grows, many stages of making electronic components from silicon wafers requires that the wafer be spun at high speeds. Being circular makes them balance easier.

Answer 4

A large (3ft long x 6dia) crystal rod is grown (not cast into a shape) from a pool of molten silicon using a small seed crystal.

The wafers are round because they are cut from a naturally shaped cylinder of grown silicon.

Answer 5

Silicon wafers are ''grown'' in a vacuum and in a perfect vacuum with no resistance the wafer assumes a perfect round shape!