Lithographic apparatus, fluid combining unit and device manufacturing method

摘要

A system for tuning the refractive index of immersion liquid in an immersion lithographic apparatus is disclosed. Two or more immersion liquids of different refractive index are mixed together in order to achieve a desired refractive index. Further, the fluids may be conditioned and treated to maintain optical characteristics.

主权项

1. A lithographic apparatus comprising:
a projection system configured to project a patterned radiation beam onto a target portion of a substrate; a movable table, located below the projection system, comprising a sensor having a detector in or on the movable table; a first liquid supply system configured to provide a first liquid with a first refractive index; a second liquid supply system configured to provide a second liquid with a second refractive index which is lower than the first refractive index; a combining unit configured to combine the first and second liquids to achieve a combined liquid with a refractive index closer to a desired refractive index than the first refractive index or the second refractive index; a refractive index measuring unit, separate from the sensor, to measure refractive index of (i) the first liquid, or (ii) the second liquid, or (iii) the combined liquid, or (iv) any combination selected from (i)-(iii); and a fluid recycling system configured to separate the first and second liquids from the combined liquid after use and to return first liquid to the first liquid supply system, wherein the combining unit is configured to combine the first and second liquids based on a measurement by the sensor of the movable table and a measurement by the refractive index measuring unit.