Effect of seasoning-layer stress on fluorine diffusion

In semiconductor thin-film deposition equipment in which a fluorine- or chlorine-based gas is used as a cleaning gas, reducing residual fluorine or chlorine inside the equipment is important for increasing production efficiency and reducing production costs. In the plasma-enhanced chemical vapor deposition process, where cleaning, seasoning, and deposition are sequentially repeated, an AlF3 layer is formed during the cleaning step with fluorine; the physical properties of the seasoning layer in contact with the AlF3 layer play an important role in fluorine diffusion. When the seasoning layer exhibits high compressive stress, the adsorbed fluorine does not diffuse and accelerates damage as it continuously concentrates on the surface of the aluminum component. We demonstrate the relationship between stress in the seasoning layer and fluorine diffusion and show that relieving compressive stress promotes fluorine diffusion, which, in turn, reduces the amount of fluorine inside aluminum components.