Fused Silica Wafers
Production and Properties of Fused Silica Wafers
Fused Silica” or “Fused Quartz” is the amorphous phase of quartz (SiO2). In contrast to e. g. borosilicate glass, fused silica has no additives, thus is pure SiO2.
Compared to normal glass, fused silica has a higher transmission in the ultraviolet and infrared spectrum, a very low thermal expansion coefficient, a high thermal resistance and softenig point, a superior chemical resistance and high dielectric strength.
One method for fused silica production is melting and re-solidifying of ultrapure SiO2. Synthetic fused silica is made from silicon-rich chemical precursors such as SiCl4 which are gasified and subsequently oxidized in a H2 + O2 atmosphere.
The SiO2 dust formed hereby is fused to silica on a substrate. This technique results in an improved optical transmission in the deep ultraviolet.
The fused silica blocks are cut into wafers, and the wafers finally polished.
Specifications of Fused Silica Wafers
JGS1 (Ultraviolet Grade Fused Silica)
These wafers show a high transparency in the ultraviolet spectral range. The transmission in the VIS and UV (down to approx. 215 nm) is approx. 90 % (only reflection losses) and drops between 215 and 150 nm down to 0 %. In the infrared range, the comparable high OH-concentration of typically 1000 ppm causes absorption bands for wavelengths > 1.2 µm.
JGS2 (Optical Grade Fused Quartz)
As compared with JGS1 wafers, the transmission range of significantly cheaper JGS2 wafers is shifted towards longer wavelengths: UV-absorption already starts below approx. 270 nm wavelength, while in the VIS and IR the transmission is approx. 90 % up to approx. 2 µm wavelength due to the lower OH-concentration (typ. < 300 ppm).
JGS3 (Full Spectrum Fused Silica)
These comparable expensive wafers with a very low OH-content (typ. < 10 ppm) show a high transparency of > 80 % over a broad spectral range of approx. 200 nm - 3 µm, and approx. 90 % in the wavelength range 250 - 2.5 µm.
Diameter and Dimensions
Available diameters are 2, 3, 4 and 6 inch. Other diameters as well as rectangular wafer pieces on request)
Standard thicknesses of fused silica wafers are 500, 700 and 1000 µm. Other thicknesses on request.
One- or double-side polished.