The manufacturing process of silicon wafers mainly consists of the crystal growth process and the wafer processing process.
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process
In the CZ method, a heater, graphite crucible, quartz crucible, and polycrystalline silicon are set in a pulling device, and are heated and melted under reduced pressure in an inert atmosphere. A single crystal is grown by attaching a seed crystal and gradually pulling it up.
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The single crystal silicon ingot for a wafer with a diameter of 300mm can reach a length of 2m and a weight exceeding 300kg, making it a very large object.
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The outer circumference of the single crystal silicon ingot is ground to achieve the specified diameter. A groove (notch) or plane (orientation flat: Ori-Flat) indicating the crystal orientation is made on part of the circumference. After that, it is cut to the specified length before slicing.
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The ingot is cut into a wafer shape using a wire saw method or an inner diameter blade method.
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To prevent chipping and cracking during the wafer manufacturing process, the edge of the wafer is ground into an arc shape using a diamond grindstone, chamfering the surface.
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The carrier with the wafer is rotated between the rotating upper and lower lapping plates, and both sides are polished by supplying abrasive grains.
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The fixture with the wafer is rotated in the etching solution mixed with acid, etching it, and completely removing the damage layer caused by the mechanical processing in the previous step.
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Heat treatment is carried out using a diffusion furnace, decomposing unstable donors (n-type impurities) originating from oxygen generated during crystal growth, and returning it to its original resistivity.
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A plate with the wafer attached is pressed against a rotating platen with a polishing cloth attached, and the polishing is continued until it becomes a mirror surface while supplying a polishing material, by mechanical and chemical combined action.
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The wafer is cleaned with chemicals and ultra-pure water, achieving chemical and physical purification.
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A high-intensity spotlight is shone on the surface of the wafer for visual inspection, and flatness, resistivity, and the number of microscopic particles adhered to the surface are also inspected using a dedicated inspection device.
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The wafer is placed in a clean shipping case and then sealed in a special bag that does not allow moisture and other elements to pass through.
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Wafers are shipped in shock-absorbing boxes designed for shipping to ensure they don't break from minor impacts.