A study on the properties of interlayer low dielectric polyimide during Cl-based plasma etching of aluminum

Al metallization on polyimide is expected to be used in advanced device structures. Since Al requires Cl-based plasma etching and a F-based plasma corrosion prevention process, the authors investigate the effects of various plasmas on polyimide properties. They find that:1) Cl plasma can be used to pattern Al metals on polyimide but over-etching might cause an increase in the dielectric constant of the polyimide film. 2) SF/sub 6/ plasma treatment is effective in replacing Cl with F, so minimization of the post-etching corrosion problem is expected. In addition, the dielectric constant of polyimide decreases after exposure to SF/sub 6/ plasma. 3) Cl and F atoms form chemical bonds with polyimide, as were analyzed by FTIR and XPS. 4) The etch rate of polyimide is much higher with SF/sub 6/ plasma as compared to Cl/sub 2/ plasma. Thus minimum exposure to SF/sub 6/ plasma for post-etching corrosion prevention is needed.