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Q: Doping of Silicon ( Answered 5 out of 5 stars,   0 Comments )
Subject: Doping of Silicon
Category: Science
Asked by: almightybob-ga
List Price: $3.00
Posted: 10 Dec 2002 11:19 PST
Expires: 09 Jan 2003 11:19 PST
Question ID: 122497
When silicon is used to make integrated circuits, it is first doped
with both n-type material and a p-type material. This causes it to
become a semiconductor.

What I want to know is how much of the n or p-type material is used in
order to successfully dope it? In other words, what percentage of
doped silicon is in fact silicon?

(I need an answer within 12 hours if possible, if for whatever reason
this does not happen, please don't answer the question and take the
money because the answer will be of no use!)
Subject: Re: Doping of Silicon
Answered By: krobert-ga on 10 Dec 2002 12:44 PST
Rated:5 out of 5 stars

It really does depend on the particular chemistry of the semiconductor
and it's intended use, but dopant elements are usually on the order of
100 ppm (but an educated range of dopant is between 10 and 1000 ppm).
Incidentally, ppm is parts per million.

Volumetrically, this usually doesn't make a difference, meaning for
all intents and purposes the semiconductor can be volumetrially just
about 100% silicon. The dopants can take a range of positions in the
silicon crystal and be either a replacement for a silicon atom in the
crystal or an interstitial atom (one that sits in the empty space
normally occupied by nothing).

Incidentally, 100 ppm is 0.01%.

Based on the above, if you were to weigh a doped silicon chip with a
non-doped silicon chip of the same size, you would not be able to tell
the difference.

The major effect of the dopant is to alter the electronic structure of
the silicon... and this does not take much dopant at all.

Best Regards,

almightybob-ga rated this answer:5 out of 5 stars
Once again a great answer from Google Answers- thanks!

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