The main factor affecting target poisoning is the ratio of reactive gas and sputtering gas. Excessive reactive gas will lead to target poisoning. During the process of reactive sputtering, the sputtering channel area on the target surface is covered by the reaction products or the reaction products are peeled off to re expose the metal surface. If the formation rate of the compound is greater than the stripping rate of the compound, the coverage area of the compound increases. Under the condition of a certain power, the amount of reaction gas involved in the formation of compounds increases, and the formation rate of compounds increases. If the amount of reaction gas increases too much, the compound coverage area will increase. If the flow rate of reaction gas cannot be adjusted in time, the rate of compound coverage area increase will not be inhibited, and the sputtering channel will be further covered by the compound. When the sputtering target is completely covered by the compound, the target will be completely poisoned and a layer of composite metal film will be deposited on the target surface. Make it hard to react again.
Poisoning phenomenon of magnetron sputtering target
1. Positive ion accumulation: when the target is poisoned, insulating oxide is formed on the surface of the target. When the positive ions reach the cathode target, due to the barrier of the insulating layer, they can not directly enter the cathode target, but accumulate on the target surface, which is easy to produce cold field arc discharge - arcing, making cathode sputtering impossible.
2. Anode disappearance: when the target is poisoned, an insulating film is also deposited on the wall of the grounded vacuum chamber, and the electrons reaching the anode cannot enter the anode, resulting in anode disappearance.
3. The performance of reactive sputtering is affected by the target "poisoning", which means that the compound film is not only formed on the substrate, but also on the sputtering target, which leads to a significant reduction in sputtering yield. Thus, the deposition rate is reduced.Causes of poisoning of magnetron sputtering target
1. Air or water leakage in vacuum chamber
2. There are volatile components in the vacuum chamber
3. If argon, air or other gases are not filled, it may cause poisoning
4. These target materials react with each other to form a black film, which affects the surface composition of the target.Poisoning treatment of magnetron sputtering target
1. The target can be recovered by using intermediate frequency source or radio frequency source for one or two hours.
2. It can also be solved by removing the target and polishing it with sandpaper.
3. Closed loop control is used to control the flow rate of reaction gas.
4. Twin targets were used.
5. Control the change of coating mode: before coating, collect the hysteresis effect curve of target poisoning, so as to control the air flow at the front of target poisoning, and ensure that the process is always in the mode before the deposition rate drops sharply.
To prevent target poisoning, first of all, ensure that the vacuum chamber does not leak, clean up the interior and remove volatile components.