Target poisoning phenomenon

Target poisoning phenomenon Reactive sputtering of the key problems in reactive sputtering (using gas with a target atom reaction generated compound membrane layer, such as oxidation film, nitride film), ion bombardment of target will be accompanied by "target poisoning" phenomenon, namely the reaction gas ion (such as O squared ⁻, N squared ⁻) with target atoms in the surface reaction of target compounds, lead to the surface properties of target change. The phenomenon of target poisoning can be classified into "mild poisoning" and "severe poisoning" based on its severity: In cases of mild poisoning, only a thin layer of compounds forms on the surface of the target material. Due to the lower sputtering yield of the compounds compared to pure metal targets, the coating rate will decline. When severe poisoning occurs, the surface of the target material is completely covered by the compound, and the sputtering process changes from "metal sputtering" to "compound sputtering". This not only significantly reduces the coating rate but may also cause the composition of the film layer to deviate from the design value. Target poisoning phenomenon is closely related to the reaction gas partial pressure. When the partial pressure of the reaction gas is relatively low, the reaction mainly occurs on the substrate surface, and the compound layer on the target material surface is relatively thin, having a smaller impact on sputtering. As the partial pressure of the reactive gas increases, the thickness of the compound layer on the target material surface increases, and the sputtering yield decreases. When the partial pressure of the reaction gas exceeds the critical value, the target material is completely poisoned, and the coating rate tends to stabilize but remains at a relatively low level. In addition, the temperature of the target material also affects the degree of target poisoning: a higher target material temperature will promote the decomposition of compounds and alleviate the phenomenon of target poisoning; However, a lower target material temperature will inhibit the decomposition of compounds and aggravate target poisoning. In industrial production, target poisoning is usually suppressed by controlling the partial pressure of the reaction gas, adjusting the current of the target material or using pulse sputtering technology to ensure the stability of the film layer quality.

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