Method for etching copper layer

A method of etching comprising:

• providing an object to be processed including a copper layer and an upper layer disposed on the copper layer within a processing container including a lower electrode on which the object to be processed is accommodated;
• forming a metal mask on the upper layer by applying a metal layer containing titanium on the upper layer and patterning the metal layer along with the upper layer with a predetermined pattern;
• supplying a processing gas including CH4 gas, oxygen gas, and a Ar gas within the processing container;
• generating plasma of the processing gas within the processing container which accommodates the object to be processed that includes the copper layer, the upper layer, and the metal mask such that (i) hydrogen ions and active carbon and/or hydrocarbon species are generated due to dissociation of the CH4 gas, (ii) Ar ions are generated due to dissociation of the Ar gas, and (iii) active oxygen species are generated due to dissociation of the oxygen gas;
• and
• supplying a radio frequency bias power to the lower electrode in order to draw the active carbon and/or hydrocarbon species, the active oxygen species, the hydrogen ions, and the Ar ions onto the object to be processed such that the metal mask is oxidized to be cured by the active oxygen species, a protective film containing carbon is formed on a surface of the metal mask by the active carbon and/or hydrocarbon species, and the copper layer is etched using the metal mask including the protective film as an etching mask while maintaining the plasma within the processing container,
• wherein forming the metal mask includes the steps of:
• (i) etching a silicon containing layer located below a resist mask to transfer a pattern of the resist mask to the silicon containing layer to form a silicon containing layer mask,
• (ii) etching an organic film layer located below the silicon containing layer mask to transfer a pattern of the silicon containing layer mask to the organic film layer to form an organic film layer mask, and
• (iii) etching the metal layer located below the organic film layer mask to transfer a pattern of the organic film layer mask to the metal layer to form the metal mask.