Lithographic apparatus, cover for use in a lithographic apparatus and method for designing a cover for use in a lithographic apparatus

Abstract

A lithographic apparatus having a fluid handling structure configured to contain immersion fluid in a space adjacent to an upper surface of a substrate table and/or a substrate located in a recess of the substrate table, a cover including a planar main body that, in use, extends around a substrate from the upper surface to a peripheral section of an upper major face of the substrate in order to cover a gap between an edge of the recess and an edge of the substrate, and an immersion fluid film disruptor configured to disrupt the formation of a film of immersion fluid between an edge of the cover and immersion fluid contained by the fluid handling structure during movement of the substrate table relative to the fluid handling structure.

1 . A lithographic apparatus comprising:
 a substrate table having an upper surface and a recess in the upper surface that is configured to receive and support a substrate;   a fluid handling structure configured to contain immersion fluid in a space adjacent to the upper surface of the substrate table and/or a substrate located in the recess;   a cover comprising a planar main body that, in use, extends around a substrate from the upper surface to a peripheral section of an upper major face of the substrate in order to cover a gap between an edge of the recess and an edge of the substrate; and   an immersion fluid film disruptor, configured to disrupt the formation of a film of immersion fluid between an edge of the cover and immersion fluid contained by the fluid handling structure during movement of the substrate table relative to the fluid handling structure.   
     
     
         2 . The lithographic apparatus according to  claim 1 , wherein the immersion fluid film disruptor comprises an edge of the cover tapered such that the thickness of the cover gradually decreases across the edge. 
     
     
         3 . The lithographic apparatus according to  claim 2 , wherein the angle of the surface of the section of the cover that is tapered, relative to the upper major face of the substrate, is selected based on one or more selected from the following: intended speed of the substrate table in use relative to the fluid handling structure when a meniscus of the fluid is over the cover, dynamic contact angle of the fluid on the cover at the intended speed, and/or the dynamic contact angle of the fluid on the substrate at the intended speed. 
     
     
         4 . The lithographic apparatus according to  claim 2 , wherein the angle of the surface of the section of the cover that is tapered, relative to the upper major face of the substrate, is in the range of from about 15° to 45°. 
     
     
         5 . The lithographic apparatus according to  claim 2 , wherein the angle of the surface of the section of the cover that is tapered, relative to the upper major face of the substrate, is such that the dynamic contact angle of the fluid on the section of the cover when a meniscus of the fluid crosses the section of the cover in use less the angle of the surface of the section of the cover is greater than the dynamic contact angle of the fluid on the substrate in use. 
     
     
         6 . The lithographic apparatus according to  claim 1 , wherein the immersion fluid film disruptor comprises a surface profile formed on the edge, an upper surface of the cover, or both, the surface profile having a plurality of local variations in the surface. 
     
     
         7 . The lithographic apparatus according to  claim 6 , wherein the local variations include ridges, channels, pimples, dimples and/or other protrusions or recesses. 
     
     
         8 . The lithographic apparatus according to  claim 2 , wherein the immersion fluid film disruptor comprises a plurality of discrete gas jets formed on a surface of the fluid handling structure opposite the upper surface of the substrate and/or substrate table. 
     
     
         9 . The lithographic apparatus according to  claim 8 , wherein the gas jets are each configured to provide a jet of gas onto the film of immersion liquid as it forms. 
     
     
         10 . The lithographic apparatus according to  claim 8 , wherein the plurality of gas jets are provided by a corresponding plurality of apertures formed in the surface of the fluid handling structure. 
     
     
         11 . The lithographic apparatus according to  claim 8 , wherein the surface of the fluid handling structure comprises a line of openings, surrounding the space in which immersion fluid is contained, configured to extract immersion fluid in order to contain the immersion fluid in the space; and the plurality of gas jets are provided outwardly of the line of openings. 
     
     
         12 . A cover for use in an immersion lithographic apparatus that includes a substrate table having a substantially planar upper surface in which is formed a recess that is configured to receive and support a substrate, the cover comprising a substantially planar main body that, in use, extends around the substrate from the upper surface to a peripheral section of an upper major face of the substrate in order to cover a gap between an edge of the recess and an edge of the substrate,
 wherein the cover comprises an immersion fluid film disruptor configured to disrupt the formation of a film of immersion fluid between the edge of the cover and immersion fluid contained by a fluid handling structure of the immersion lithographic apparatus during movement of the substrate table relative to the fluid handling structure.   
     
     
         13 . A method of designing a cover for use in an immersion lithographic apparatus that includes a substrate table having a substantially planar upper surface in which is formed a recess that is configured to receive and support a substrate, the cover comprising a substantially planar main body that, in use extends around the substrate from the upper surface to a peripheral section of an upper major face of the substrate in order to cover a gap between an edge of the recess and an edge of the substrate, wherein an edge of the cover is tapered such that the thickness of the cover gradually decreases across the edge; and the method comprises selecting the angle of the surface of the section of the cover that is tapered, relative to the upper major face of the substrate, in order that the section of the cover in use disrupts the formation of a film of immersion fluid between the edge of the cover and the immersion fluid contained by a fluid handling structure of the lithographic apparatus during movement of the substrate table relative to the fluid handling structure. 
     
     
         14 . The method of designing a cover according to  claim 13 , wherein the angle of the surface of the section of the cover that is tapered, relative to the upper major face of the substrate, is selected based on one or more selected from the following: intended speed of the substrate table in use relative to the fluid handling structure when a meniscus of the fluid is over the cover, dynamic contact angle of the fluid on the cover at the intended speed, and dynamic contact angle of the fluid on the substrate at the intended speed. 
     
     
         15 . The method of designing a cover according to  claim 13 , further comprising forming the cover according to the design. 
     
     
         16 . A cover for use in an immersion lithographic apparatus, manufactured according to a design provided by a method of designing the cover for use in an immersion lithographic apparatus that includes a substrate table having a substantially planar upper surface in which is formed a recess that is configured to receive and support a substrate, the cover comprising a substantially planar main body that, in use extends around the substrate from the upper surface to a peripheral section of an upper major face of the substrate in order to cover a gap between an edge of the recess and an edge of the substrate, wherein an edge of the cover is tapered such that the thickness of the cover gradually decreases across the edge; and the method comprising selecting the angle of the surface of the section of the cover that is tapered, relative to the upper major face of the substrate, in order that the section of the cover in use disrupts the formation of a film of immersion fluid between the edge of the cover and the immersion fluid contained by a fluid handling structure of the lithographic apparatus during movement of the substrate table relative to the fluid handling structure.