Applying "the upgraded Berg model" to predict hysteresis free reactive sputtering

• Different strategies for obtaining hysteresis free processes
• Modeling of the reactive sputtering processes at different processing conditions
• The influence from reactivity and sputtering yields on the hysteresis effect.
• The influence from pumping speed, target size, and pressure on hysteresis effect

Reactive sputtering is a popular process to deposit oxides, nitrides, and several other compounds. Unfortunately, this process mostly exhibits a hysteresis effect. The hysteresis causes a delicate choice of either a high deposition rate but not a fully oxidized/nitrided film or a fully formed compound film but at a significantly lower deposition rate. For high reactivity target material/reactive gas systems, the hysteresis forces the process to flip quite abrupt between these two conditions. Process control may therefore be quite critical.In this work we will use the original “Berg model” as well as the newly published “upgraded Berg model” to illustrate how hysteresis is generated. We have selected one simple graph (reactive gas flow vs. partial pressure) that gives clear indications of how the process may be affected in such a way as to decrease or even eliminate the hysteresis. Specific values of target size and composition, gas mixture as well as total pressure and pumping speed are processing parameters that may be selected in a way to eliminate hysteresis. We will show that this behavior is predicted by the simulations and also refer to experimental evidence for such behavior.