Process of magnetron sputtering

2019-10-22

In recent years, with the development of new materials, the development and application of thin film materials, the development of sputtering deposition technology has played an important role in scientific research and industrial production. During the sputtering process, the target material is made of the material to be deposited, fixed on the cathode of the sputtering system, and the substrate of the thin film to be deposited is placed on the anode facing the target surface. When the sputtering system is pumped to a high vacuum and filled with argon, a high voltage is applied between the cathode and the anode, and a low-voltage glow discharge is generated between the cathode and the anode. In the plasma generated by the discharge, positive ions of argon move toward the cathode under the action of the electric field and collide with the target surface. Target atoms that are sputtered from the target surface by collision are called sputter atoms. The energy of the sputtered atoms is generally in the range of one to several tens of electron volts. Sputtering atoms are deposited on the surface of the substrate to form a thin film. Sputtering coating is the use of argon positive ions generated by low-voltage glow discharge to bombard the cathode target under the action of a high-speed electric field, spray the atoms or molecules in the target, and deposit it on the surface of the substrate or workpiece to form the required film layer. However, the energy of the sputtered particles during the sputtering process is very low, resulting in a low film formation rate.

The magnetron sputtering technology is developed on the basis of sputter coating, and the purpose is to increase the film formation rate. Establish a magnetic field orthogonal to the electric field on the target surface to increase the ionization rate of argon from 0.3% to 0.5% to 5% to 6%. It solves the problem of low deposition rate of sputtering coating, one of the main methods of precision coating in the industry. There are many types of cathode target materials. Metals, alloys, and ceramics can be used to make targets. Under the dual effects of vertical magnetic field and electric field, magnetron sputtering coating has the advantages of fast deposition speed, dense film layer, and good bonding with the substrate, etc., which is suitable for large-scale and high-efficiency industrial production.
In the magnetron sputtering process, the specific process has a great impact on the film properties. The main process flow is as follows:
(L) Substrate cleaning, mainly using isopropanol vapor cleaning, then soaking the substrate with ethanol and acetone, and drying to remove surface oil stains;
(2) When vacuuming, the degree of vacuum should be controlled above 2 × 10-4 pa to ensure the purity of the film;
(3) Heating. In order to remove the moisture on the surface of the substrate and improve the adhesion between the film and the substrate, the substrate needs to be heated. The temperature is generally between 150 ° C and 200 ° C.
(4) The partial pressure of argon is generally in the range of 0.01-lpa to achieve the atmospheric pressure conditions of discharge;
(5) Pre-sputtering, that is, removing the oxide film on the target surface by ion bombardment, so as not to affect the quality of the film;
(6) Under the effect of orthogonal magnetic field and electric field, positive ions formed by sputtering and argon ionization bombard the target at high speed, so that the target particles reach the surface of the substrate and are deposited into a thin film;
(7) After annealing, the thermal expansion coefficient of the film is different from that of the substrate, and the bonding force is small.