Magnetron sputtering vacuum coating machine adopts magnetron sputtering technology, but during the coating process, flameout often occurs, commonly known as poisoning. Then why does the phenomenon of target poisoning occur, and what causes it? The following is a brief introduction to the vacuum editor, hoping to help everyone.

First: the formation of metal compounds on the target surface.
        In the process of forming the compound from the metal target surface through the reactive sputtering process, where is the compound formed? Since the reactive gas particles collide with the atoms on the target surface to generate chemical reaction to generate compound atoms, which is usually an exothermic reaction, the heat generated by the reaction must have a way of conduction, otherwise, the chemical reaction cannot continue. Heat transfer between gases is impossible under vacuum, so chemical reactions must take place on a solid surface. Reactive sputtering products are performed on target surfaces, substrate surfaces, and other structured surfaces. Generating compounds on the substrate surface is our goal. Generating compounds on other surfaces is a waste of resources. Generating compounds on the target surface was initially a source of compound atoms, but later became an obstacle to continuously supplying more compound atoms.
        Second: the influencing factors of target poisoning

        The main factor affecting target poisoning is the ratio of reactive gas to sputtering gas. Excessive reactive gas will lead to target poisoning. During the reactive sputtering process, the sputtering channel region on the target surface is covered by the reaction product or the reaction product is peeled off to re-exposed the metal surface. If the rate of compound formation is greater than the rate at which the compound is stripped, the area covered by the compound increases. In the case of a certain power, the amount of reaction gas participating in the formation of the compound increases, and the compound formation rate increases. If the amount of reactive gas increases excessively, the area covered by the compound increases. If the flow rate of the reactive gas cannot be adjusted in time, the rate of increase in the area covered by the compound cannot be suppressed, and the sputtering channel will be further covered by the compound. When the sputtering target is completely covered by the compound When the target is completely poisoned

        Third: the phenomenon of target poisoning
        (1) Positive ion accumulation: When the target is poisoned, an insulating film is formed on the target surface. When positive ions reach the cathode target surface, due to the blocking of the insulating layer, they cannot directly enter the cathode target surface, but accumulate on the target surface, which is prone to cold field. Arc-induced discharge --- arcing, so that the cathode sputtering can not continue. (2) Anode disappears: When the target is poisoned, an insulating film is also deposited on the wall of the grounded vacuum chamber, and electrons reaching the anode cannot enter the anode, resulting in the disappearance of the anode.
Fourth: Physical explanation of target poisoning
      (1) In general, the secondary electron emission coefficient of metal compounds is higher than that of metals. After the target is poisoned, the surface of the target is covered with metal compounds. After being bombarded by ions, the number of secondary electrons released increases, which improves the space efficiency. The turn-on capability reduces the plasma impedance, resulting in a lower sputtering voltage. Thus, the sputtering rate is reduced. In general, the sputtering voltage of magnetron sputtering is between 400V and 600V. When target poisoning occurs, the sputtering voltage will be significantly reduced. (2) The sputtering rate of metal target and compound target is different. Generally, the sputtering coefficient of metal is higher than that of compound, so the sputtering rate is low after the target is poisoned. (3) The sputtering efficiency of reactive sputtering gas is inherently lower than that of inert gas, so when the proportion of reactive gas increases, the overall sputtering rate decreases.
        In the magnetron sputtering vacuum coating machine, the target poisoning is very unfavorable for the coating period, which will cause many unnecessary failures and losses. Because for the solution to poisoning, coating experts have also developed a set of solutions to prevent target poisoning to solve this problem, and I will give you a detailed introduction next time.