Optical unit, exposure apparatus, and device manufacturing method

Abstract

In a barrel of an optical unit a ring shaped support member is integrally arranged, and three projected portions are arranged on the upper surface of the support member. The projected portions support a lower surface of a parallel flat plate supported in direct contact. In this supported state, the parallel flat plate opposes a surface of the support member with a clearance of several μm in between. With this arrangement, the space in one side of the parallel flat plate is substantially isolated from the space in the other side. Accordingly, for example, even if gas environment in the space on one side of the parallel flat plate is different from the other side, gases can be effectively kept from mixing. In addition, since the parallel flat plate is supported at three coplanar points, deformation of the parallel flat plate can be suppressed due to the force supporting the parallel flat plate, thereby suppressing the index of refraction from varying.

What is claimed is:  
     
         1 . An optical unit that has an optical path of light inside a barrel, said optical unit comprising: 
 a plate shaped transmissive optical element which transmits said light; and    a first support member attached to said barrel, said first support member having 
 a first opposing surface opposing an outer periphery portion of said optical path on a surface of said transmissive optical element, and  
 at least three of a first projected portion arranged on said opposing surface which makes a predetermined first clearance in between said surface of said transmissive optical element and said first opposing surface that almost isolates space formed on a surface side of said transmissive optical element from space formed on the other surface side of said transmissive optical element, by supporting said transmissive optical element in at least three points.  
   
     
     
         2 . The optical unit of  claim 1  wherein 
 said barrel is at least partly cylindrical including a part where said first support member is attached, and  
 said transmissive optical element has a circular outer periphery.  
 
     
     
         3 . The optical unit of  claim 2  wherein 
 said first support member has a circular opening formed which makes said optical path, and  
 said transmissive optical element is arranged in a state where a ring-shaped protruding portion protrudes outside said circular opening.  
 
     
     
         4 . The optical unit of  claim 2  wherein said transmissive optical element is an optical element that functions as a lens.  
     
     
         5 . The optical unit of  claim 1  wherein a contact surface of said transmissive optical element with said first projected portion is one of a planar and a curvature surface.  
     
     
         6 . The optical unit of  claim 1 , further including an exhaust unit that performs forced exhaustion of gas via a space between said transmissive optical element and said first opposing surface of said first support member.  
     
     
         7 . The optical unit of  claim 6  wherein said exhaust unit has a ring shaped exhaust groove which is formed on said first opposing surface of said first support member and structures a part of a gas exhaust path.  
     
     
         8 . The optical unit of  claim 1 , further comprising: 
 a second support member which clamps said transmissive optical element with said first support member, said second support member having 
 a second opposing surface which opposes an outer periphery portion of said optical path on a surface on the other side of said transmissive optical element, and  
 at least three of a second projected portion arranged on said second opposing surface which makes a predetermined second clearance in between said surface on the other side of said transmissive optical element and said second opposing surface, by each making contact with said transmissive optical element at positions opposing said first projected portions.  
   
     
     
         9 . The optical unit of  claim 8  wherein said first projected portions and said second projected portions are arranged at a position opposing each other with said transmissive optical element in between at three points.  
     
     
         10 . The optical unit of  claim 8  wherein a contact surface of said transmissive optical element with said second projected portion is one of a planar and a curvature surface.  
     
     
         11 . The optical unit of  claim 8  wherein 
 said barrel is at least partly cylindrical including a part where said first support member is attached,  
 said transmissive optical element has a circular outer periphery,  
 circular openings making said optical path are formed on said first support member and said second support member, respectively, and  
 said transmissive optical element is arranged in a state so as to form a ring shaped protruded portion protruding outside each of said circular openings.  
 
     
     
         12 . The optical unit of  claim 11  wherein said transmissive optical element is an optical element that functions as a lens.  
     
     
         13 . The optical unit of  claim 8 , further including an exhaust unit that performs forced exhaustion of gas via a space between said transmissive optical element and said second opposing surface of said second support member.  
     
     
         14 . The optical unit of  claim 13  wherein said exhaust unit has a ring shaped exhaust groove which is formed on said second opposing surface of said second support member and structures a part of a gas exhaust path.  
     
     
         15 . An exposure apparatus that exposes a substrate with an energy beam to form a predetermined pattern on said substrate, said exposure apparatus comprising: 
 an optical unit which projects said energy beam via said pattern onto said substrate, said optical unit including 
 a barrel which inside is an optical path of said energy beam, and  
 a first isolating mechanism having 
 a plate shaped first transmissive optical element transmitting said energy beam arranged on said optical path of said energy beam, and  
 a first support member attached to said barrel supporting said first transmissive optical element in at least three first supporting portions so that at least a part of said first support member opposes an outer periphery portion of said optical path on one surface of said first transmissive optical element with a predetermined first clearance in between, whereby  
 said first mechanism isolates space in said one surface side of said first transmissive optical element from space in the other surface side of said first transmissive optical element.  
 
   
     
     
         16 . The exposure apparatus of  claim 15  wherein each of said first supporting portions is a projected portion provided on a surface of said first support member opposing said surface side of said first transmissive optical element.  
     
     
         17 . The exposure apparatus of  claim 15  wherein said first isolating mechanism further has: 
 a second support member which clamps said first transmissive optical element with said first support member by making contact with the other surface side of said first transmissive optical element via a second supporting portion located at a position opposing each of said first supporting portions, and  
 at least a part of said second support member opposes an outer periphery portion of said optical path on the other surface side of said first transmissive optical element with a predetermined second clearance in between.  
 
     
     
         18 . The exposure apparatus of  claim 17  wherein each of said second supporting portions is a projected portion provided on a surface of said second support member opposing the other surface side of said first transmissive optical element.  
     
     
         19 . The exposure apparatus of  claim 15  wherein 
 said barrel houses a projection optical system which projects said predetermined pattern onto said substrate, and  
 said first transmissive optical element is arranged on an object surface side of said projection optical system.  
 
     
     
         20 . The exposure apparatus of  claim 19  wherein said optical unit further has 
 a second isolating mechanism having 
 a plate shaped second transmissive optical element transmitting said energy beam, arranged on an image plane side of said projection optical system, and  
 a second support member attached to said barrel, supporting said second transmissive optical element in at least three second supporting portions so that at least a part of said second support member opposes an outer periphery portion of said optical path on one surface side of said second transmissive optical element with a predetermined second clearance in between, whereby  
 said second mechanism isolates space in said one surface side of said second transmissive optical element from space in the other surface side of said second transmissive optical element.  
 
 
     
     
         21 . The exposure apparatus of  claim 20  wherein each of said second supporting portions is a projected portion provided on a surface of said second support member opposing said surface side of said second transmissive optical element.  
     
     
         22 . The exposure apparatus of  claim 20  wherein said second isolating mechanism further has 
 a third support member which clamps said second transmissive optical element with said second support member by making contact with the other surface side of said second transmissive optical element via third supporting portions located at positions opposing each of said second supporting portions, and  
 at least a part of said third support members oppose an outer periphery portion of said optical path on the other surface side of said second transmissive optical element with a predetermined third clearance in between.  
 
     
     
         23 . The exposure apparatus of  claim 22  wherein each of said third supporting portions is a projected portion provided on a surface of said third support member opposing the other side of said surface side of said second transmissive optical element.  
     
     
         24 . The exposure apparatus of  claim 20 , said exposure apparatus further comprising: 
 a mask chamber connected in a sealed state to said barrel, said mask chamber housing within a mask on which said pattern is formed; and    a substrate chamber connected in a sealed state to said barrel, said substrate chamber housing within a substrate stage on which said substrate is held, wherein 
 low absorptive gas having low absorptive properties to said energy beam is supplied into each of said barrel, said mask chamber, and said substrate chamber, and  
 said first isolation mechanism isolates said absorptive gas in between the inside of said barrel and the inside of said mask chamber, while said second isolation mechanism isolates said absorptive gas in between the inside of said barrel and the inside of said substrate chamber.  
   
     
     
         25 . The exposure apparatus of  claim 15 , said exposure apparatus further comprising: 
 a mask chamber connected in a sealed state to said barrel, said mask chamber housing within a mask on which said pattern is formed, wherein 
 low absorptive gas having low absorptive properties to said energy beam is supplied into each of said barrel and said mask chamber, and said first isolation mechanism isolates said absorptive gas in between the inside of said barrel and the inside of said mask chamber.  
   
     
     
         26 . The exposure apparatus of  claim 25  wherein 
 a flange portion that makes a holding member hold said barrel is arranged on a periphery portion of said barrel, and  
 a partition wall of said mask chamber is connected to said flange portion.  
 
     
     
         27 . The exposure apparatus of  claim 25  wherein 
 a flange portion that makes a holding member hold said barrel is arranged on a periphery portion of said barrel, and  
 said low absorptive gas is supplied into said barrel via a gas supply path formed in said flange portion.  
 
     
     
         28 . The exposure apparatus of  claim 25  wherein said low absorptive gas supplied into said mask chamber and said barrel is a different type of gas.  
     
     
         29 . The exposure apparatus of  claim 15 , said exposure apparatus further comprising: 
 a substrate chamber connected in a sealed state to said barrel, said substrate chamber housing within a substrate stage on which said substrate is held, wherein 
 low absorptive gas having low absorptive properties to said energy beam is supplied into each of said barrel and said substrate chamber, and said first isolation mechanism isolates said absorptive gas in between the inside of said barrel and the inside of said substrate chamber.  
   
     
     
         30 . The exposure apparatus of  claim 29  wherein 
 a flange portion that makes a holding member hold said barrel is arranged on a periphery portion of said barrel, and  
 a partition wall of said substrate chamber is connected to said flange portion.  
 
     
     
         31 . The exposure apparatus of  claim 29  wherein said low absorptive gas supplied into said substrate chamber and said barrel is a different type of gas.  
     
     
         32 . The exposure apparatus of  claim 15  wherein said energy beam belongs to light in vacuum ultraviolet region having a wavelength of 190 nm and under.  
     
     
         33 . A device manufacturing method including a lithographic process, wherein in said lithographic process exposure is performed using said exposure apparatus according to  claim 15 .  
     
     
         34 . The optical unit of  claim 8  wherein said first clearance and said second clearance are a clearance that suppresses gas from flowing in between spaces on one side of said transmissive optical element and the other side of said transmissive optical element.  
     
     
         35 . The exposure apparatus of  claim 17  wherein said first clearance and said second clearance are a clearance that suppresses gas from flowing in between spaces on one side of said first transmissive optical element and the other side of said first transmissive optical element.  
     
     
         36 . The exposure apparatus of  claim 22  wherein said second clearance and said third clearance are a clearance that suppresses gas from flowing in between spaces on one side of said second transmissive optical element and the other side of said second transmissive optical element.