Wafer production - wafer material
Wafers are the basic product for the production of solar cells; 200 - 400µm thin silicon slices, which are manufactured to solar cells. Depending on the production method, different wafer materials have to be distinguished - monocrystalline and polycrystalline.
Different production processes and processing techniques create a common end product - thin silicon slices - wafers.
All of them having a different energy conversion rate, depending on the way they are produced.
- monocrystalline wafers
The single silicon crystal (ingots) produced in the Czochralski method is the basic product for monocrystalline wafers.
In several steps the pulled and more than 2m long single crystal has it's end pieces taken of (detecting inclusions and cropping) and is cut into workable cylinders with i.e. a band saw. The cylinders obtained from that are fixed to a carrier and then cut into thin slices - wafers - using a wire saw.
- polycrystalline wafers
Band saws divide the casted silicon blocks created into smaller qubes with defined measures (e.g. 125 x 125 mm)
In several steps the cuboid is cut with a band or inside hole saw.
The silicon cuboid prepared by this is affixed to a carrier material and can then be cut into small slices, so-called wafers, with a wire saw.
Diamond-studded saw blades or wires respectively produce silicon wafers with a thickness of < 200µm - 400µm. Silicon carbid (SiC) is used as cutting support. Polyethylene glycol (PEG) or oil is applied as cooling or mold release agent. Area of wire 100-300 µm - qubes with defined measures 125mm - number of wafer approx. 175 - 400.