METHOD AND APPARATUS FOR COMPENSATING FOR THE EFFECTS OF GRAVITY ON A PELLICLE USED FOR PROTECTING A RETICLE FROM CONTAMINATION

摘要

A pellicle membrane ( 1 ) is connected to a frame ( 3 ), substantially parallel to a reticle base plate ( 5 ), so as to define an enclosure with a space ( 9 ) between the reticle carried on the base plate ( 5 ) and the pellicle membrane ( 1 ). A mask ( 6 ) is provided on the reticle within the enclosure. A bore hole ( 11 ) is provided in a side wall of the frame ( 3 ) into the enclosure. A mechanism ( 13 ) for adjusting the air pressure in the space ( 9 ) to compensate for the effect of gravity on the pellicle membrane ( 11 ), comprises a piston member ( 15 ) within a housing ( 17 ) which is closed at one end, so that a chamber ( 19 ) is defined at the closed end of the housing ( 17 ). A bore hole ( 21 ) is provided in a wall of the housing ( 17 ) into the chamber ( 19 ) and a tube or pipe ( 23 ) between the bore hole ( 11 ) and the bore hole ( 21 ) defines a gas path between the space ( 9 ) and the chamber ( 19 ). A moveable said piston member ( 15 ) determines the necessary gas pressure in said space ( 9 ), to compensate for the effect of gravity on said pellicle membrane ( 1 ). Fine tuning can be achieved by changing the mass of the piston member ( 15 ) by, for example, attaching weights ( 25 ) thereto.