Color zen chapter 5 level 204/24/2023 The weight of the wafer goes up along with its thickness and diameter. The tabulated thicknesses relate to when that process was introduced, and are not necessarily correct currently, for example the IBM BiCMOS7WL process is on 8-inch wafers, but these are only 200 μm thick. Wafer thickness is determined by the mechanical strength of the material used the wafer must be thick enough to support its own weight without cracking during handling. Wafers grown using materials other than silicon will have different thicknesses than a silicon wafer of the same diameter. Intel, TSMC, and Samsung were separately conducting research to the advent of 450 mm " prototype" (research) fabs, though serious hurdles remain. The diameter has gradually increased to improve throughput and reduce cost with the current state-of-the-art fab using 300 mm, with a proposal to adopt 450 mm. Semiconductor fabrication plants, colloquially known as fabs, are defined by the diameter of wafers that they are tooled to produce. Silicon wafers are available in a variety of diameters from 25.4 mm (1 inch) to 300 mm (11.8 inches). Wafer properties Standard wafer sizes Silicon The generated PSG ( phosphosilicate glass) is removed from the edge of the wafer in the etching. When used for solar cells, the wafers are textured to create a rough surface to increase surface area and so their efficiency. One of the most effective methods is RCA clean. There are several standard cleaning procedures to make sure the surface of a silicon wafer contains no contamination. Wafers are cleaned with weak acids to remove unwanted particles. The largest wafers made have a diameter of 450 mm, but are not yet in general use. Electronics use wafer sizes from 100 to 450 mm diameter. The size of wafers for photovoltaics is 100–200 mm square and the thickness is 100–500 μm. The boule is then sliced with a wafer saw (a type of wire saw), machined to improve flatness, chemically etched to remove crystal damage from machining steps and finally polished to form wafers. Donor impurity atoms, such as boron or phosphorus in the case of silicon, can be added to the molten intrinsic material in precise amounts in order to dope the crystal, thus changing it into an extrinsic semiconductor of n-type or p-type. In this process, a cylindrical ingot of high purity monocrystalline semiconductor, such as silicon or germanium, called a boule, is formed by pulling a seed crystal from a melt. One process for forming crystalline wafers is known as the Czochralski method, invented by Polish chemist Jan Czochralski. Nearly defect-free single crystalline material, with a purity of 99.9999999% ( 9N) or higher.
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