Vacuum pump, Vacuum technology for the next generation.


CVD / Plasma CVD (Chemical Vapor Deposition)


Here, we summarize the principles of vacuum.
Now it’s time to explain about CVD.
CVD is a three-letter combination of CD and DVD, but of course it has nothing to do with it.
Let’s keep up the good work.

What is CVD?

CVD is an acronym for Chemical Vapor Deposition.
chemical means chemical, vapor means steam or vaporized gas, and deposition means adhesion (deposition). In Japanese, “chemical vapor deposition” or “chemical vapor phase” means. It is called “vapor deposition” or “chemical vapor deposition”.

Here’s a quick review.
So far, you have explained “thin-film deposition (strictly speaking, physical vapor deposition)” and “stappering” as methods for forming a thin film on a substrate using vacuum. Both of these are methods called PVD (Physical Vapor Deposition) because solid materials are evaporated and atomized to adhere.

On the other hand, CVD (Chemical Vapor Deposition) is characterized by using gaseous molecules as raw materials. The raw material gas (* 1) and carrier gas (* 2) are supplied into the container on which the substrate or base material is placed, and energy (heat, plasma, light, etc.) for decomposition and reaction is given to it for chemistry. It is a method of making a thin film by reacting.

“Thermal CVD”, which uses heat as the energy for chemical reaction, is generally classified as “plasma CVD” or “optical CVD” for each energy.


* 1also called source gas, is a vaporized compound containing the element to be coated. Silane (SiH4), tungsten hexafluoride (WF6), etc. are available.

* 2Carrier gas is the gas that is sent to the surface of the substrate together with the raw material gas. It plays the role of evenly diffusing the raw material gas in the container. Hydrogen (H), nitrogen (N), argon (Ar), etc. are used.


Features of CVD

In CVD, the raw material spreads evenly with gaseous molecules and adheres firmly to the surface by a chemical reaction, so it is possible to form a more uniform and adhered thin film even on uneven substrates.
Since the thin film can be formed quickly and the area that can be processed is large, it has the advantage of excellent mass productivity.

However, on the other hand, as the name suggests, thermal CVD, which is the most used method, requires a reaction at a high temperature (near 1000 ° C), so a gas that does not react at a high temperature cannot be used. Since there is a risk that the heat-sensitive substrate (plastic, etc.) will also be deformed, it cannot be used.

Even if it seems to be a great method, there are good and bad things, so it seems important to understand the characteristics of the raw material and the substrate and use it properly with PVD etc.

Plasma CVD appeared there

However, “thermal CVD” is not the only method of CVD. As I mentioned earlier, there is something called “plasma CVD”.

Plasma CVD is a method of decomposing a raw material gas into a plasma state and causing a chemical reaction to occur in the active state. Due to this special method, a thin film can be formed at a temperature of room temperature to 600 ° C with the same quality as thermal CVD.

Plasma CVD still has its characteristics. By converting the raw material into plasma and changing the type and composition ratio, it is possible to control the characteristics (refractive index, stress, insulation, etc.) of the thin film.

However, plasma CVD also has its drawbacks.
The substrate and coating surface are easily damaged by ions, and the work is performed under reduced pressure, so the efficiency of using the raw material gas is slightly lower. If the conditions are bad, it will be difficult to generate plasma, and control will be complicated.

Various technologies are playing an active role by utilizing the special environment of vacuum state.

What is it used for?

It is often used in the production of electronic devices
and semiconductor devices.

  • Insulating film for display devices such as liquid crystal displays
  • Amorphous Si semiconductors for solar cells
  • Insulating film for semiconductor devices
  • Compound semiconductor film such as GaAs of light emitting elements such as LEDs
  • Films such as SiC, Si3N4, AIN, PBN, DLC (diamond-like carbon) used for coating heat-resistant containers and parts
  • CNT (carbon nanotube) film