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The differences are the result of the difference in their manufacturing process.
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FUSED QUARTZ
Naturally occurring crystalline (sand) is crushed into powder and passes through numerous purifying processes. The resulting pure powder is fused by either of two different processes to manufacture clear fused quartz ingots.
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FUSED SILICA
The manufacturing of this form of Silicon Dioxide does not uses naturally occurring material but it is derived synthetically. Hence the name synthetic quartz.
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Electrically Fused
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Flame Fused
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High energy electrical heating process melts (fuses) the powder, casting very large ingots which will be cut up during fabrication.
The result of this process is a fairly pure material. This material has a very low Hydroxil (OH) content. It does however contains some fine bubbles and minute amount of other contaminants. Currently this is the most widely used material in the semiconductor industry. It is also used in some optical applications where low cost and commercial grade quality is acceptable.
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In this process particular chemicals are fused with
Oxygen - Hydrogen flame.
This material processing involves various drying processes, thus numerous grades are available with different OH content. This material have excellent optical characteristic and it is suitable for most optically critical applications. Because the OH content effects the maximum processing temperatures of the wafer substrate this parameter should be carefully evaluated. |
Flame Fused
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DRY - Fused
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| In this manufacturing process the powder is fused with Oxygen - Hydrogen flame. This clear fused quartz material extremely pure and virtually bubble free. However the OH content is somewhat higher than the electric fused quartz. This material is appropriate for almost all but the most demanding optical applications.
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This process to manufacture synthetic quartz is one of the latest advancement in this technology.
This method produces the highest grade material to date. The extremely low OH contents allows for high processing temperatures. The optical characteristics are of the highest grade. |