知識力

❒ Features of PECVD
Plasma Enhanced Chemical Vapor Deposition (PECVD) has the chemical reaction occurred in the process of film growth, so it belongs to Chemical Vapor Deposition (CVD). Because PECVD needs High Vacuum (HV) and the evaporated film may be rapidly deposited on the substrate in a large amount, so the cost is lower and it’s suitable for mass production in factory. PECVD is often used for producing metal leads of integrated circuit, diamond protective film for hard discs, etc.

❒ Processing flow of PECVD
Making the example of growing diamond-like poly crystal film, as shown in Fig. 1, the processing steps are as follows:
1. Placing Si wafer on top of wafer table of PECVD machine as substrate
2. Under high vacuum, introducing methane (CH4) into the reactor
3. Applying high energy electromagnetic wave on methane, called Radio Frequency (RF), to break the chemical bonds of methane (CH4) and form methane plasma, i.e. carbon ions (with positive charges)
4. Carbon ions (with positive charges) will be attracted by the negative electrode (with negative charges) and move toward Si wafer (substrate), so as to be deposited on the substrate to form diamond-like film. 
 
 
Figure 1: Illustration of PECVD system.
 

It should be noted that the atom size (lattice constant) of Si wafer is much different from the carbon atom size of diamond, so it is nearly impossible to grow real diamond epitaxy on Si wafer, but to form poly crystal or amorphous carbon film. Because it is not a real diamond epitaxy, it is called “Diamond Like Carbon (DLC).” Although DLC is not real diamond, the transparency and hardness are nearly the same as the real diamond and thus DLC is often grown on the material surface as high-hardness protective film. For example, DLC may be grown on the surface of cutter to enhance the hardness of cutter. It is called “diamond cutter” that can easily cut any material.
 
【Remark】
Metal Organic Chemical Vapor Deposition (MOCVD) and Plasma Enhanced Chemical Vapor Deposition (PECVD) are actually very similar, wherein MOCVD utilizes the heating method to enable the gas generating chemical reaction, but PECVD utilizes the plasma method to enable the gas generating chemical reaction.

【Remark】The aforementioned contents have been appropriately simplified to be suitable for reading by the public, which might be slightly differentiated from the current industry situation. If you are the expert in this field and would like to give your opinions, please contact the writer. If you have any industrial and technical issues, please join the community for further discussion.