Vapor deposition techniques and their classification
Vapor deposition is a technique for forming functional film layers on the surface of a substrate. It is the deposition of middle or multi-layer, simple or compound film layers on the surface of a product by using the physical or (and) chemical reactions of the substance in the gas phase, so as to obtain various excellent properties required on the surface of the product.
As a surface coating method, the basic step of vapor deposition is to vaporize, transport and finally deposit the materials that need to be plated. Its main feature is that no matter whether the original materials need to be plated are solid, liquid or gas, they must be transformed into vapor phase morphology for migration during transportation and finally reach the surface of the workpiece for deposition and condensation.
There are two kinds of vapor deposition, chemical vapor deposition and physical vapor deposition.
At first, the volatile liquid TiCl was slightly heated to obtain the TiCl gas and NH3 gas, which were introduced into the high-temperature reaction chamber together. These reaction gases were decomposed, and then chemical reactions following thermodynamic principles were carried out on the high-temperature solid surface to generate TiN and HCL. HCL was removed and TiN was deposited on the solid surface to form a hard solid film. Chemical vapor deposition is the process by which a nonvolatile solid deposit is formed by a chemical reaction on a solid surface between a volatile compound and a gaseous substance containing elements constituting a thin film.
At the same time, people put another kind of vapor deposition, through high temperature heating of metal or metal compounds evaporated into gas phase, or through electronic, plasma, and the photon can charge particles can show the metal or compound target sputtering out corresponding atoms, ions, molecules (gas), deposit into a solid film on a solid surface, which does not involve physical chemical reactions (decomposition or combined), known as physical vapor deposition, with the vapor deposition technology development and application of the above two types of vapor deposition each have new technique and technology content, a cross between the two, is difficult to strictly distinguish between chemistry or physics.For example, plasma and ion beam are introduced into the evaporation and sputtering of traditional physical vapor deposition technology to participate in the coating process. At the same time, reactive gas is introduced into the process. Chemical reactions can also be carried out on the solid surface to generate new synthetic solid phase film, which is called reactive plating.The reaction gas N2 was introduced into the sputtering titanium (Ti) plasma and TiN was synthesized as an example.This means that physical vapor deposition can also involve chemical reactions.In indoor ventilation into the reaction of methane, for example, with the help of W target cathode arc discharge, plasma in Ar, W under the action of the methane decomposition, and the solid surface to recombine the carbon bonds, generate mixed W diamond-like carbon film, people used to place on the deposition process in chemical vapor deposition, but it is in a typical physical vapor deposition technology, metal cathode arc ion plating.In addition, people put the plasma, ion beam technology into the traditional Chemical Vapor Deposition process, Chemical reaction has not fully follow the traditional thermodynamics principle, because the plasma has better Chemical activity, can be much lower than the traditional Chemical reaction thermodynamics implementation under the temperature of reaction, the method known as the plasma Assisted Chemical Vapor Deposition (Plasm Assisted Chemical Vapor Deposition, PACVD;Some materials are called plasma enhanced chemical vapor deposition (PECVD), which gives chemical vapor deposition more physical meaning.
Now, the only difference between chemical vapor deposition and physical vapor deposition is the morphology of the coating materials. The former USES volatile compounds or gaseous materials, while the latter USES solid (or liquid) materials. This distinction seems to have lost the essence of the original definition.
We according to the existing habits, mainly in the plating material form to distinguish the difference between a chemical vapor deposition, physical vapor deposition, the solid (liquid) plating material through high temperature and evaporation, sputtering, electron beam, plasma, ion beam, laser beam and arc, and other forms of energy produced by gas atoms, molecules, ions transport (gas, plasma), condensation of solid deposition on the surface (including chemical reactions with other gas phase reaction substances generated reaction products), to generate solid phase membrane process known as physical vapor deposition.
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