Method for enhancing etch selectivity of metal silicide film to polysilicon film, and method for etching stacked film of metal silicide film and polysilicon film

摘要

An etching method in which the etch selectivity of a metal silicide film with respect to a polysilicon film can be increased when a polycide film is etched by plasma enhanced etching, is provided. This method is accomplished by repeating (a) plasma etching the metal silicide film with a plasma source power applied to an etch chamber, using etch gas ions accelerated by applying a bias power to a substrate, and (b) chemically adsorbing the etch gas ions on the metal silicide film and oxidizing the polysilicon film exposed using the etch gas ions, by continuously applying the plasma source power to the etch chamber and preventing application of the bias power applied to the substrate or applying a level of bias power at which the etch gas ions are not accelerated. Accordingly, an etch prevention film is formed on only a polysilicon film which is exposed by modulating a bias power, upon plasma etching of a polycide film, thereby increasing the etch selectivity of a metal silicide film with respect to the polysilicon film. Thus, during etching of the polycide film, a substrate can be prevented from being damaged due to abnormal etching of the polysilicon film, thus increasing the reliability of semiconductor devices.