In semiconductor manufacturing equipment, numerous core components employ surface coating treatment methods: that is, a functional film is constructed on the surface of metal, ceramic and other base components. In simple terms, the surface coating process involves applying film material using various treatment methods onto the base of the component, forming a complete and continuous solid film, thereby endowing the part with various usage properties such as corrosion resistance and insulation. According to the differences in implementation principles, the current mainstream surface coating methods in the industry are mainly divided into six technical routes, namely PVD, thermal spraying, CVD, electroplating, electrochemistry and organic coating process. Below, these six mainstream surface coating technologies will be explained separately.
PVD
PVD belongs to a typical vacuum film-forming technology. It does not involve the decomposition of chemical precursors. It uses physical effects to convert the target material into atoms or ions, which then migrate and deposit onto the substrate surface, forming thin and dense functional films. It mainly includes vacuum evaporation, sputtering coating, ion plating, and aerosol deposition (AD). It is widely used in industrial ceramic products such as alumina ceramic parts, aluminum nitride ceramic substrates, and silicon carbide ceramic structural components.
Vacuum evaporation heats the target material in a vacuum environment. The released particles migrate and settle to form thin films; sputtering coating uses high-energy ions to bombard and strip the target material atoms to complete deposition; ion plating ionizes the particles to enhance the bonding strength between the film layer and the substrate. Aerosol deposition is a special PVD process that can prepare ceramic hard films at low temperatures, suitable for precision industrial ceramic components with limited heat resistance and ceramic insulating bases. PVD films have high purity and accuracy, and can be used to prepare hard protective films and optical functional films, suitable for the harsh conditions of semiconductor equipment ceramic-metal composite components and special-shaped industrial ceramic products.
Thermal Spraying
Thermal spraying is a high-temperature melting-based surface modification process, commonly used for oxidized alumina ceramic components, ceramic bearing bases, silicon carbide ceramic protective parts, and metal parts in semiconductor equipment. Its principle is to use a heat source to heat the powder or filamentous coating material to a molten or semi-molten state, and then spray it onto the workpiece surface through high-speed airflow. The particles impact the substrate and stack up, forming a protective solid coating layer layer by layer.
According to the heat source and working environment, the sub-processed techniques include flame spraying, plasma spraying, and arc thermal spraying. Flame spraying relies on a gas flame to melt the material, with low equipment costs; plasma spraying relies on an ultra-high temperature plasma arc to melt high-melting-point ceramics; arc thermal spraying uses metal wire to start the arc and melt the raw material, mostly used for metal coatings. Atmospheric plasma spraying can be processed in air and is suitable for preparing heat-resistant and anti-corrosion coatings for industrial ceramics; high-density plasma spraying optimizes the arc source parameters to enhance the kinetic energy and heat energy of the particles, reducing the coating porosity and suitable for semiconductor particle erosion conditions.
CVD
CVD forms films through gas-phase chemical reactions. It is widely used in aluminum nitride ceramic substrates, silicon carbide ceramic cavity components, and ceramic insulating parts. Unlike PVD which forms films through physical phase transformation, CVD introduces gaseous precursors containing the film-forming elements into the reaction chamber. Under specific temperature and pressure conditions, these precursors decompose and combine, and the solid products continuously deposit on the surface of the workpiece, growing uniform and continuous functional coatings.
Electroplating Coating Technology
Electroplating is an important surface modification method for semiconductor components. It is applicable to metal substrates as well as pre-treated ceramic metallized parts, ceramic connection bases, and composite ceramic functional components. Through chemical or electrochemical reactions, a metal protective coating is constructed on the substrate, and it is divided into electroplating and chemical plating types.
Traditional electroplating relies on an external power supply to form an electrolytic circuit. Metal ions on the conductive substrate are reduced and precipitated to form a coating, enhancing the conductivity and wear resistance of the parts. Chemical plating does not require an external power supply. It relies on the reducing agent in the plating solution for oxidation-reduction reactions. Even for irregular industrial ceramic metallized components, it can obtain uniform thickness coatings, and has good adaptability to complex shapes such as grooves and curved surfaces.
Electrochemical coating technology
Electrochemical coating generates an oxidation conversion film in situ on the substrate through electrolysis. In the semiconductor field, anodization is representative, and it is mostly used for aluminum-based components. It is often combined with ceramic-aluminum composite components and ceramic mounting bases for surface strengthening. The workpiece is placed in the electrolyte, and the electric field drives the substrate metal to oxidize, generating a dense oxide film in situ, which belongs to a substrate transformation type coating. Anodization can enhance the hardness and chemical corrosion resistance of the workpiece, and it also has certain insulation effects. In some scenarios, it can be used for coloring.
Organic coating technology
Organic coatings use high-molecular materials to protect the surface of components. They can be applied to metal substrates, as well as activated industrial ceramics auxiliary parts and ceramic external bases. They are divided into coating by paint application and electrophoretic coating.
Coating by paint application sprays or brushes liquid high-molecular coatings onto the workpiece, which solidifies into a film to prevent moisture and chemical media, achieving anti-corrosion; electrophoretic coating relies on an electric field to make the coating particles deposit directionally, and irregular workpieces can also obtain uniform thickness coatings. In semiconductor equipment, this process is often combined with ceramic peripheral support parts to provide rust and corrosion protection for the external frame and non-process cavity components of the equipment.
Summary
The above six coating processes are the key surface treatment methods for semiconductor equipment components. They can perform surface modification on metals as well as industrial ceramic substrates such as aluminum oxide, aluminum nitride, and silicon carbide, as well as structural components. Each process has its own characteristics. In practical applications, it is necessary to combine the working conditions of the components, and select them individually or in combination based on indicators such as high-temperature resistance, resistance to plasma corrosion, insulation, and wear resistance, to meet the strict usage conditions of semiconductor manufacturing.
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