Vacuum Furnace

Chemical vapor deposition (CVD) is a technology that uses various energy sources such as heating, plasma excitation or light radiation to chemically react gaseous or vapor chemical substances on the gas phase or gas-solid interface to form solid deposits in the reactor by means of chemical reaction.To put it simply, two or more gaseous raw materials are introduced into a reaction chamber, and then they react with each other to form a new material and deposit it on the substrate surface.

CVD furnace is one combined furnace system with high temperature tube furnace unit,gases control unit, and vacuum unit, it is widely used for experiment and production of composite material preparation, microelectronics process, semiconductor optoelectronic, solar energy utilization, optical fiber communication, superconductor technology, protective coating field.

CVD furnace system consists of high temperature tube furnace unit, reacting gas source precise control unit, vacuum pump station and corresponding assembling parts.

Vacuum pump is to remove the air from the reacting tube,and make sure there is no unwanted gases inside the reaction tube, after that the tube furnace will heat the reaction tube to a target temperature, then reacting gas source precise control unit can introduce different gases with a set ratio into the furnace tube for the chemical reaction, the chemical vapor deposition will be formed in the CVD furnace.

There are tremendous gas sources can be used in the CVD process, the common chemical reactions of CVD includes Pyrolysis, photolysis, reduction, oxidation, redox,so the gases involved in these chemical reactions can be used in the CVD process.

We take CVD Graphene growth for an example, the gases used in the CVD process will be CH4,H2,O2 and N2.

• Wide range of films can be produced, metal film, nonmetal film and multi-component alloy film as required. At the same time, it can prepare high-quality crystals that are difficult to obtain by other methods, such as GaN, BP, etc.
• The film forming speed is fast, usually several microns per minute or even hundreds of microns per minute. It is possible to simultaneously deposit large quantities of coatings with uniform composition, which is incomparable to other film preparation methods, such as liquid phase epitaxy (LPE) and molecular beam epitaxy (MBE).
• The working conditions are carried out under normal pressure or low vacuum conditions, so the coating has good diffraction, and the workpieces with complex shapes can be uniformly coated, which is much superior to PVD.
• Due to the mutual diffusion of reaction gas, reaction product and substrate, a coating with good adhesion strength can be obtained, which is crucial for preparing surface strengthened films such as wear-resistant and anti-corrosion films.
• Some films grow at a temperature far lower than the melting point of the film material. Under the condition of low temperature growth, the reaction gas and reactor wall and impurities contained in them almost do not react, so a film with high purity and good crystallinity can be obtained.
• Chemical vapor deposition can obtain a smooth deposition surface. This is because compared with LPE, chemical vapor deposition (CVD) is carried out under high saturation, with high nucleation rate, high nucleation density, and uniform distribution on the whole plane, resulting in a macroscopic smooth surface. At the same time, in chemical vapor deposition, the average free path of molecules (atoms) is much larger than LPE, so the spatial distribution of molecules is more uniform, which is conducive to the formation of a smooth deposition surface.
• Low radiation damage, which is a necessary condition for manufacturing metal oxide semiconductors (MOS) and other devices

PECVD is a technology that uses plasma to activate reaction gas, promote chemical reaction on the surface of substrate or near surface space, and generate solid film. The basic principle of plasma chemical vapor deposition technology is that under the action of RF or DC electric field, the source gas is ionized to form a plasma, the low-temperature plasma is used as the energy source, an appropriate amount of reaction gas is introduced, and the plasma discharge is used to activate the reaction gas and realize chemical vapor deposition.

According to the method of generating plasma, it can be divided into RF plasma, DC plasma and microwave plasma CVD, etc...

The difference between PECVD and traditional CVD technology is that the plasma contains a large number of high-energy electrons, which can provide the activation energy required in the chemical vapor deposition process, thus changing the energy supply mode of the reaction system. Since the electron temperature in the plasma is as high as 10000K, the collision between electrons and gas molecules can promote the chemical bond breaking and recombination of the reaction gas molecules to generate more active chemical groups, while the whole reaction system maintains a lower temperature.

So compared to the CVD process, PECVD can carry out the same chemical vapor deposition process with a lower temperature.