Fluid pressure compensation for immersion litography lens
AssigneeNikon Corporation
InventorsDouglas C. Watson, W. Thomas Novak
Life of this patent
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Abstract
An immersion lithography system compensates for displacement of the final optical element of the optical assembly caused by the immersion fluid. The system includes an optical assembly to project an image defined by a reticle onto a wafer. The optical assembly includes a final optical element spaced from the wafer by a gap. An immersion element supplies an immersion fluid into the gap and recovers any immersion fluid that escapes the gap. A fluid compensation system applies a force to the final optical element of the optical assembly to compensate for pressure variations of the immersion fluid.
Claims26
A method used in a liquid immersion lithography apparatus, the method comprising:
- measuring a pressure in a gap between a wafer and an optical member of the liquid immersion lithography apparatus in which the wafer is exposed through a liquid filled in the gap during immersion lithography;
- and
- adjusting a distance between the wafer and an immersion device of the liquid immersion lithography apparatus, wherein the immersion device supplies the liquid.
A liquid immersion lithography apparatus comprising:
- a wafer table that supports a wafer;
- an optical assembly that projects an image of a pattern onto the wafer held by the wafer table, the optical assembly including a final optical element spaced from the wafer by a gap;
- an immersion nozzle that supplies an immersion liquid to the gap between the final optical element and the wafer;
- a pressure sensor that measures a pressure in the gap between the final optical element and the wafer;
- and
- a control system that adjusts a distance between the immersion nozzle and the wafer based on the pressure measured by the pressure sensor.
Dependencies are inferred from the claim text.