Reactive ion etching of the fluorinated polyimide film

The etch conditions affecting the etching of the fluorinated polyimide films in RF plasma using oxygen or fluorine-containing oxygen has been investigated. The effect of power, oxygen gas flow rate, and gas composition on the etch rate of fluorinated polyimide have been determined. The etch rate of the fluorinated polyimide increases linearly with the power and oxygen gas flow. The saturation at high oxygen flow rate indicates a saturation or steady state achieved at the polyimide-oxygen reaction interface. However, the etch rate increases when CF₄ is added to oxygen, up to about 10% CF₄ in O₂, and then decreases to a smaller and CF₄ concentration independent value. The etch selectivity of hard mask against fluorinated polyimide has been determined. The PECVD silicon nitride and PETEOS are found to be excellent hard mask for pattering these polyimides. The trench profile of the polyimide film also has been examined by patterning and etching the different trench sizes in fluorinated polyimide. It is concluded that this fluorinated polyimide can be etched with oxygen or fluorine containing oxygen plasma.