All semiconductor materials require purification of the raw materials, and the required purity is 6 "9" or more, up to 11 "9" or more. The purification method is divided into two categories, one is to purify without changing the chemical composition of the material, which is called physical purification; the other is to first purify the element into a compound, and then reduce the purified compound into an element, called Chemical purification. The methods of physical purification include vacuum evaporation, regional refining, and crystal pulling purification. The most used one is regional refining. The main methods of chemical purification include electrolysis, complexation, extraction, rectification, etc. The most used is rectification. Since each method has certain limitations, a combination of several purification methods is often used to obtain a qualified material.
Most semiconductor devices are fabricated on a single wafer or an epitaxial wafer with a single wafer as the substrate. Batches of semiconductor single crystals are all made by melt growth. The Czochralski method is the most widely used, and 80% of silicon single crystals, most of the germanium single crystals, and indium telluride single crystals are produced by this method, in which the maximum diameter of the silicon single crystal has reached 300 mm. The Czochralski method in which a magnetic field is introduced into the melt is called a magnetron crystal pulling method, and a highly uniform silicon single crystal has been produced by this method. A liquid covering agent is added to the surface of the crucible melt to be a liquid-sealed straight-drawing method, and a single crystal having a large decomposition pressure such as gallium arsenide, gallium phosphide or indium phosphide is drawn by this method. The melt of the suspension zone is not in contact with the vessel, and a high purity silicon single crystal is grown by this method. The horizontal zone melting process is used to produce tantalum single crystals. The horizontal orientation crystallization method is mainly used for preparing gallium arsenide single crystal, and the vertical orientation crystallization method is used for preparing cadmium telluride and gallium arsenide. The bulk single crystal produced by various methods is subjected to crystal orientation, barreling, reference surface, slicing, grinding, chamfering, polishing, etching, cleaning, detecting, encapsulating, etc., to provide a corresponding wafer.
The growth of a single crystal thin film on a single crystal substrate is called epitaxy. Epitaxy methods include gas phase, liquid phase, solid phase, molecular beam epitaxy, and the like. Industrial production uses mainly chemical vapor phase epitaxy, followed by liquid phase epitaxy. Vapor phase epitaxy and molecular beam epitaxy of metal organic compounds are used to prepare microstructures such as quantum wells and superlattices. Amorphous, microcrystalline, and polycrystalline films are often formed on substrates such as glass, ceramics, and metals by various types of chemical vapor deposition, magnetron sputtering, and the like.
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Label: Practical use of semiconductor materials
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