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Silicon Wafers

1. From Quartz Sand to Silicon Wafers

Silicon in the Universe and on Earth
The visible matter of the universe is dominated by hydrogen and helium, and the mass fraction of Silicon is less than 0.1 %. The entire terrestrial globe contains approx. 17 % Silicon. In the approx. 40 km thick earth crust, Silicon (in form of silicates and SiO₂) with a mass fraction of 26 % is the second most element after oxygen.

Production of metallurgical-grade Silicon
Quartz sand (SiO₂) is reduced with carbon in an electric arc furnace at > 1900°C to metallurgicalgrade Silicon (> 98 % pure). The major part of the world production (2008: approx. 6 million tons) is used for manufacturing alloys with Aluminium and steel, only a small fraction is used for silicon wafer production..

Purification of Silicon
The impurity concentration of metallurgical-grade Silicon is many orders of magnitude too high for Silicon wafer production. Therefore, Silicon is converted into trichlorosilane gas (HSiCl₃) using hydrochloric acid. Multiple distillation of HSiCl₃ improves the purity up to 99,9999999 %. After thermal decomposition of the of HSiCl₃ to polycrystalline Silicon, monocrystalline Silicon as base material for Si wafers is formed via two alternative techniques, as described in the following section.

2. Silicon Ingot Production

Czochralski-Technique
With this technique, a small monocrystalline seed crystal which defines the crystallographic orientation (e. g. <100>, <110> or <111>) of the finally realized Si wafers pulls a monocrystal with the same crystallographic orientation out of melted poly-Si. The pull velocity (some mm ... cm per hour) determines the crystal diameter, additives in the melted Silicon allow crystal doping. The advantages of the Czochralski-Technique are: Big possible crystal diameters, comparable low-cost technique. Disadvantages: Impurities from the crucible and inhomogeneous doping which make it impossible to realize high-ohmic Silicon wafers with this technique.

Float-Zone Technique
Hereby, a monocrystalline seed crystal is brought into contact with a polycrystalline Si ingot. Starting from here, an RF coil melts the poly-Si which, after cooling down, forms monocrystalline Si with the crystallographic orientation of the seed crystal. Doping is realized during crystal growth from the gaseous phase. The advantages of the float-zone technique are: No impurities from the crucible and homogeneous doping which allow high-ohmic FZ Silicon wafers with a resistivity > 100 ohm cm. The disadvantages of the FZ technique are: High cost process, limited crystal diameter.

3. From the Ingot to Finished Silicon Wafers

The ingot is cut and ground to the required length and diameter. An orientation flat is added to indicate the crystal orientation of the Silicon wafers. The edge of the sliced wafers is ground to attain the specified diameter. Then the wafers are etched to remove the damaged surface resulting from the previous lapping. Finally, It is polished (either single- or double-side) to a mirror surface by a combined mechanical-chemical action, and cleaned.

Optionally, the finished Silicon wafers are oxidized (SiO₂-wafers) or coated with e. g. silicon nitride (Si₃N₄-wafers)

4. Our Wafers
Since 2010, a network of Silicon wafer manufacturers allows us to supply various semiconductor wafers in a very flexible way, such as

• Si wafer with different diameter, doping, surfaces and orientation
• Si wafers with SiO₂ and Si₃N₄ coating
• Single wafers up to entire lots
• Prime wafers and low-priced "dummy"-wafers (wider specs, e. g. for litho-tests)

5. Si-Wafers-Stock List: Our Si-Wafer stock list

Here you can find a list of immediately and soon available Silicon wafers with different diameter (2, 3, 4, 6 and 8 inch), crystallographic orientation ( <100>, <110> or <111>), surface (single- or double-side polished), thickness and resistivity.

6. Your Request for Si-Wafers
Please fill in your specifications for Si-Wafer here. The fields signed with * are obligatory. Submit this form by clicking the "Send Form" button  (end of this page). Thank you!