Method for etching euv material layers utilized to form a photomask

A method of etching an ARC layer or an absorber layer disposed on a photomask, comprising:

• transferring a film stack into an etching chamber, the film stack having an ARC layer disposed on an absorber layer partially exposed through a patterned photoresist layer;
• providing a first gas mixture including at least one fluorine containing gas in to a processing chamber;
• applying a first source RF power to form a plasma from the first gas mixture to etch the ARC layer;
• applying a first type of RF bias power to the substrate for a first period of time;
• applying a second type of RF bias power away from the substrate for a second period of time;
• and
• etching the ARC layer through the patterned photoresist layer in the presence of the plasma.

A method of etching an ARC layer and an absorber layer disposed on a photomask, comprising:

• transferring a film stack into an etching chamber, the film stack having an ARC layer disposed on an absorber layer partially exposed through a patterned photoresist layer;
• providing a first gas mixture including at least one fluorine containing gas in to a processing chamber;
• applying a first type of RF bias power to the substrate for a first period of time;
• applying a second type of RF bias power away from the substrate for a second period of time;
• etching the ARC layer through the patterned photoresist layer in the presence of the plasma;
• providing a second gas mixture including at least one fluorine containing gas in to the same processing chamber;
• applying a third type of RF bias power to the substrate for a third period of time;
• applying a fourth type of RF bias power away from the substrate for a fourth period of time, wherein first RF bias power is higher than the third RF bias power.