Plasma treatment is a technology that changes the surface properties of polymer materials and also changes the surface morphology of materials. Polymer materials can be easily made hydrophilic or water-repellent by plasma treatment. During the modification process, water repellent or hydrophilic groups are introduced to the surface of the polymer material due to the reaction in the plasma state. In the plasma state reaction, the excited state particles play a very important role. First, the excited state particles capture the hydrogen atoms on the main chain of the polymer to form free radicals, and then the main chain free radicals react with other excited state particles or free radicals to produce water repellent or hydrophilic groups on the surface of the polymer material, so that the material has water repellent or hydrophilic. On the other hand, other particles ( such as electrons, ions, etc. ) in the plasma state continuously bombard the surface of the material during the reaction process, triggering a degradation reaction on the surface of the material. As a result, a large number of low molecular products were generated on the surface of the material, and the surface of the material was eroded.

Therefore, in the process of plasma surface treatment, the introduction group reaction and degradation reaction occur simultaneously on the surface of the material. The degradation reaction is the reaction that we hope to avoid in the experiment. In order to avoid this harmful reaction, people have improved the plasma modification technology and put forward the concept of remote plasma.

Remote plasma treatment is to place the experimental sample far away from the plasma treatment area. Traditional plasma treatment is usually called direct plasma treatment or conventional plasma treatment to distinguish remote plasma treatment. The plasma contains electrons, ions and excited particles. These particles disappear in the recombination process ( electron and positive ion recombination, positive ion and negative ion recombination, excited state particles and excited state particles recombination ), and their recombination rates are : 10-7,10-7,10-33cm3 / s, respectively. 

Therefore, the lifetime of excited particles in plasma is longer than that of electrons and ions. The remote plasma technology is proposed based on the different survival life of various active particles in the plasma atmosphere. Like conventional plasma, the remote plasma region contains active particles such as excited atoms, ions, molecules, and molecular fragments. However, due to the proper separation of the treatment region and the discharge region, the concentration of short-lived electrons and ions decays rapidly, so the concentration of chemically active ions such as long-lived metastable atoms and active radicals is high. At the same time, the harmful effects of electrons, ions and other particles on the surface of the material are reduced as much as possible.

Remote plasma not only has the characteristics of conventional plasma, but also has the following advantages : the energy of active particles in the remote region is moderate, the plasma polymerization reaction is mild, the side reaction is less, and the controllability is strong. The discharge area is separated from the treatment area, which reduces the damage to the carrier material and the deposited polymer caused by ion bombardment, ultraviolet radiation and electromagnetic field of excitation source ( such as microwave ). Plasma polymerization can be carried out on the surface of sensitive carrier materials ; since the monomer can be introduced in the downstream region of the plasma, the direct action of the high-energy active particles on the monomer molecules in the plasma discharge region is avoided, and the structure of the deposited film is easy to control and the purity is high. The polymerization of the monomer on the container wall or the inner electrode surface is reduced.