PVD Coating Materials Overview
(1) Overview of thin film material preparation technology
Thin film materials grow on top of substrate materials (such as screen glass, optical glass, etc.), generally formed by metal, non-metal, alloy or compound materials after coating, with increased transmission, absorption, cutoff, spectroscopy, reflection, filtering, interference, protection, waterproof and anti-fouling, anti-static, electrical conductivity, magnetic conductivity, insulation, abrasion resistance, high temperature resistance, corrosion resistance, oxidation resistance, radiation protection, decoration and composite functions, and can improve product quality, environmental protection, energy saving, extend product life, improve the original performance, etc.
Currently, thin film material preparation technologies mainly include.
Physical Vapor Deposition (PVD) technology and Chemical Vapor Deposition (CVD) technology.
①PVD technology
PVD technology is one of the main technologies for the preparation of thin film materials, which refers to the technology of depositing thin film materials with certain special functions on the surface of substrate materials through a low-pressure gas (or plasma) process by physically vaporizing the surface of a substance into gaseous atoms, molecules or partially ionized into ions under vacuum conditions. The substances used to prepare thin film materials under PVD technology are collectively referred to as PVD coating materials.
After years of development, PVD technology has become the mainstream coating method, mainly including sputtering coating and vacuum evaporation coating.
A. Sputtering Coating
Sputtering coating is a technique that uses ions generated by an ion source, which are accelerated and gathered in a vacuum to form a high-velocity ion beam, to bombard the surface of a solid, where the ions and the atoms on the solid surface exchange kinetic energy, causing the atoms on the solid surface to leave the solid and be deposited on the surface of the substrate material. The solid being bombarded is the raw material for depositing thin film materials by sputtering method, called sputtering target.
Generally speaking, sputtering target is mainly composed of target blank, back plate (or back tube) and other parts, among which, target blank is the target material bombarded by high-speed ion beam, which belongs to the core part of sputtering target. Because the sputtering target needs to be installed inside the special equipment to complete the sputtering process, the equipment is a high voltage, high vacuum working environment, most of the target blank material is soft or highly brittle, not suitable for direct installation in the equipment, therefore, need to be bound with the back plate (or back tube), the back plate (or back tube) mainly plays a fixed sputtering target role, and has good electrical and thermal conductivity.
The basic principle of sputtering coating is as follows：
The sputtering coating process is reproducible, the film thickness can be controlled, and a uniform film thickness can be obtained on a large area of the substrate material, and the prepared film has the advantages of high purity, good denseness, and strong bonding with the substrate material. Therefore, the demand for sputtering targets, a functional material with high added value, is increasing year by year, and sputtering targets have become the most used PVD coating material in the market at present.
There are many types of sputtering targets, and even the sputtering targets of the same material have different specifications. According to different classification methods, sputtering targets can be divided into different categories, the main classification is as follows：
B、Vacuum evaporation coating
Vacuum evaporation coating is a deposition technology that uses the heat energy of a film heating device (called evaporation source) under vacuum conditions to evaporate a substance by heating to deposit it on the surface of a substrate material. The substance to be evaporated is the raw material for depositing thin film material by vacuum evaporation coating method, which is called evaporation coating material.
Vacuum evaporation coating system generally consists of three parts: vacuum chamber, evaporation source or evaporation heating device, substrate placement and heating device for the substrate. In order to evaporate the material to be deposited in the vacuum, a container is needed to support or hold the evaporated material, and evaporation heat is needed to bring the evaporated material to a high enough temperature to generate the required vapor pressure.
The basic principle of vacuum evaporation coating is as follows：
Vacuum evaporation coating technology is a widely used coating technology with the features of simple and convenient, easy operation and fast film formation, and is mainly applied to the coating of small-sized substrate materials.
CVD Technology
CVD technology relies on chemical reaction at high temperature, introducing the vapor of gaseous reactant or liquid reactant containing the elements of thin film and other gases required for the reaction into the reaction chamber, and generating thin film materials by chemical reaction on the surface of substrate.
2、Main PVD coating materials
(1) Sputtering target
Sputtering target is the target material for high-speed charge energy particle bombardment, which has the characteristics of high purity, high density, multi-component, uniform grain, etc. It is generally composed of target blank and backing plate (or backing tube). According to the different raw materials used, sputtering targets can be divided into metal/non-metal monolithic targets, alloy targets, compound targets, etc.
(2) Vapor deposition materials
Using different raw materials, formulations and processes, hundreds of vapor deposition materials have been developed so far, and some of the main products are described as follows：
