[Rockhounds] Silicon metal vs Silica / attacking quartz without hydrofluoric acid

[Al Balmer]

On Wed, 26 Dec 2007 15:49:00 -0800, "Erich Kern"
<efkern at earthlink.net> wrote:

>
>The semiconductor industry doesn't use quartz, but the electronics industry does, to make frequency selective resonators (known as 'crystals' in the trade) and frequency filters. I used to work for the Collins-Rockwell facility in Calif., in the 1970's that did this. They bought the lab grown quartz crystals from a firm named Hoffman. The quartz crystals were lab grown in electrically heated pressure vessels at roughly 800 C. temperature. The raw silica for the growth medium was dissolved in concentrated sodium hydroxide, as Bryan Kramer (I think it was Bryan) said. Nasty stuff!

Motorola made their own. I was involved in supplying and programming
the system which controlled the process. About a thirty day batch
cycle, as I remember.
>
>Ultra pure silicon metal is used to make semiconductors (transistors, diodes and integrated circuits), and solar panels. I don't know how the metallic silicon is separated out of SiO2, perhaps there are intermediate steps. After the raw silicon metal is extracted it goes through a "zone melt" refining process in a vacuum chamber several times, where all of the impurities migrate to one end of the silicon boule. 

One of several methods. I worked in a research lab during the summer
of 1958 where we were growing ultra-pure silicon by vapor deposition
from silicon tetrachloride.
>
>Cheers,
>Erich Kern
>Murrieta, CA
>
>
>----- Original Message ----- 
>From: DonH 
>To: Rockhounds at drizzle.com: A mailing list for rock and gem collectors 
>Sent: Wednesday, December 26, 2007 11:02 AM
>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
>
>
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-- 
Al Balmer
Sun City, AZ