摘要
CF4 gas chemistry is widely used in plasma strip process as addition to other main chemistry such as oxygen (O-2) and nitrogen (N-2) because of its benefit of removing Si contained residue or some other inorganic crust layers. However, it is not widely accepted due to the concern for the chamber ash rate shift during mixing run conditions. In this article, low ratio CF4 addition downstream plasma impact is studied on the chamber ash rate with substrate temperature <300 degrees C. It is found that CF4 contained process impacted the chamber condition and cause ash rate shift of O-2/N-2 or O-2/4%H-2-N-2 Forming Gas (FG) ash process. The CF4 gas ratio, running accumulation sequence and chamber post condition impact on the chamber ash rate are analyzed. The results from this study also provide one effective way to avoid ash rate drop post CF4 contained process.