Lithography apparatus and method for operating the same

A method, comprising:

• transferring a wafer coated with a photoresist layer onto a wafer stage;
• and
• performing a lithographic exposure process to the photoresist layer by using an extreme ultraviolet (EUV) tool, the EUV tool comprising:
• an EUV illumination source;
• a pellicle and a photomask on a downstream optical path of the EUV illumination source, wherein the pellicle covers a patterned region of the photomask, the pellicle comprises a pellicle frame disposed on a non-patterned region of the photomask, the pellicle frame has a vent hole having a first port on an inner surface of the pellicle frame and a second port on an outer surface of the pellicle frame, wherein the first port of the vent hole is at an elevation different from an elevation of the second port of the vent hole;
• and
• a plurality of optics on a reflective path from the photomask.

An apparatus, comprising:

• an extreme ultraviolet (EUV) light source;
• a first plurality of optics positioned on a downstream optical path of the EUV light source;
• a pellicle and a photomask positioned on a downstream optical path of the first plurality of optics, wherein the pellicle overlaps with a patterned region of the photomask, the pellicle comprises a pellicle membrane and a pellicle frame disposed between the pellicle membrane and a non-patterned region of the photomask, the pellicle frame has a vent hole that allows for a flow of air passing through the pellicle frame, wherein at least a portion of an inner surface of the vent hole extends in a direction non-parallel with a bottom surface of the photomask;
• a second plurality of optics positioned on a reflective path from the photomask;
• and
• a wafer stage positioned on a downstream optical path of the second plurality of optics.