[Rockhounds] attacking quartz without hydrofluoric acid

[gene at fossilnut.com]

Silicon for semi-conductors starts with relatively pure sources of sand or 
solid silica. The silica is washed and treated to remove impurities but it 
does not stop there since even parts per trillion impurities these days can 
be a problem. It used to be only parts per billion but as circuits have 
gotten smaller and faster, the tolerance for impurities has gone down.

Beyond that the silica is dissolved (made into a silane), purified, and 
chemically fused with a reducing agent  (hydrogen) and recrystallized as 
silicon. Later it gets remelted, doped with equally pure elements such as 
boron and crystallized under controlled conditions into large single crystal 
ingots with a specific crystal orientation, since the manufacturing process 
for the chips cannot tolerate crystal boundaries. When finished a single 
slice from the crystal makes hundreds or thousands of chips.

 I suspect there are even more steps but these are the major ones I am aware 
of.

Silica is also precipitated as colloidal silica, and used as a polishing 
agent for the chips.


Gene Hartstein


----- Original Message ----- 
From: "DonH" <donhalterman at verizon.net>
To: "Rockhounds at drizzle.com: A mailing list for rock and gem collectors" 
<rockhounds at lists.drizzle.com>
Sent: Wednesday, December 26, 2007 2:02 PM
Subject: Re: [Rockhounds] attacking quartz without hydrofluoric acid


> Lanny wrote:
>
>> Doesn't the semiconductor industry work with silicon, the metal, not 
>> silica, the oxide? There must be a whole world of difference in 
>> dissolving silicon as compared to dissolving silica (quartz).
>
>
> But where do they get the silicon?  I think there are quartz mines with 
> relatively pure quartz used for semiconductors.  I can't think of too many 
> ways besides acids to get the silicon isolated (then again I'm not a 
> chemist).
>
> Best,
> Don
>
>
> -- 
> _______________________________________________
> Rockhounds at drizzle Mailing List
> Subscription Services:
> http://lists.drizzle.com/mailman/listinfo/rockhounds
> List Home Page, with a link to the List Usage Policy:
> http://www.eclecticlapidary.com/Rockhounds/index.html
>