Diffusion Method Of Solar Power Generation System
Author: Source: Datetime: 2016-09-28 17:04:55
Liquid source diffusion
Liquid source diffusion is the use of protective gas, through the source bottle and carry impurities into the reaction chamber steam, impurity vapor decomposition at high temperatures, and with the silicon surface reaction, the formation of impurity element atoms in the silicon around the saturation impurity vapor pressure, Silicon wafer surface to the internal diffusion. Liquid source devices commonly used in silicon planar processes. In order to obtain better diffusion uniformity and repeatability, N2 is generally divided into two streams. The smaller flow rate is used to carry impurity source steam (small N2), and the larger flow is used to dilute impurity source steam (N2).
Liquid source diffusion, liquid source diffusion has many advantages, such as the diffusion layer is good, knot formation even, low cost, high efficiency, repeatability and uniformity, easy operation, so widely used in production. Solar power generator liquid source for diffusion is typically trimethyl borate, tripropyl borate, boron tribromide and the like. Boron tribromide will react to produce boron trioxide, boron trioxide in the 900 ℃: about silicon and react to generate boron atoms and deposited on the silicon surface to form a layer containing a large number of boron atoms of SiO2, known as boron silicon Glass, borosilicate glass boron atoms at high temperatures will continue to spread to the inside of the silicon wafer surface in the formation of a high concentration of impurity layer.
Liquid phosphorus diffusion, for phosphorus diffusion, commonly used phosphorus source POCl3, POCl5 and so on. POCl3 is a kind of impurity source which is widely used in the diffusion of phosphorus. It is a colorless transparent liquid with pungent smell. If the purity is not high, POCl3 is red and yellow, the specific gravity is 1.67, the melting point is 2 ℃ and the boiling point is 107 ℃. solar power generator. Very easy to hydrolysis, highly volatile. POCl3 above 600 ℃ can occur decomposition reaction, the formation of P2O5, at high temperature and the reaction of silicon SiO2 and phosphorus atoms, they are attached to the silicon surface to form phosphorus silicon glass, which continue to spread phosphorus atoms in silicon to form a certain concentration of impurities Distribution and junction depth.
Solid state source diffusion
Diffusion commonly used solid-state sources are B2O5, SbO3, BN, calcium phosphate glass, the main types of diffusion and open-tube diffusion of the proliferation of two.
Box diffusion method is to diffuse the wafer and the impurity source (usually oxide) in a certain sealed box (box made of quartz), under the protection of nitrogen for high temperature diffusion. The open-tube diffusion of the boron nitride source is the same as that of the silicon wafer, used portable solar power generator and is equidistantly placed in the quartz boat, into the diffusion furnace and heated and diffused under the protection of nitrogen.
Solid - solid diffusion
Solid-solid diffusion is formed by chemical vapor deposition or colloid coating on the surface of a silicon wafer to form a solid layer (doped oxide layer or doped polysilicon layer) containing impurities for portable solar power generator, and then solidifying the solid To diffuse into the silicon. This has the advantage that the surface concentration can be controlled.
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