Patent Publication Number: US-2007096764-A1

Title: Immersion exposure apparatus and method of manufacturing semiconductor device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2005-313256, filed Oct. 27, 2005, the entire contents of which are incorporated herein by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to an immersion exposure apparatus and a method of manufacturing a semiconductor device.  
      2. Description of the Related Art  
      The reduced size and increased integration level of semiconductor devices have made what is called immersion exposure important; the immersion exposure is a technique for carrying out exposure with a liquid such as water interposed between a substrate to be exposed and a projection lens in an exposure apparatus. However, with the immersion exposure, the liquid remaining on the surface of the substrate may disadvantageously flow out of the substrate, which contaminates the apparatus.  
      To solve this problem, Jpn. Pat. Appln. KOKAI Publication No. 2004-193252 proposes a structure that prevents the liquid from flowing out. However, this proposal poses various problems because the structure is fixed to the apparatus. For example, when the substrate is set on a substrate holding unit (wafer chuck or the like), the structure disadvantageously constitutes an obstacle to the setting of the substrate.  
      Thus, with the immersion exposure, the liquid for the immersion exposure may disadvantageously contaminate the apparatus. However, not all the conventional immersion exposure apparatuses comprise appropriate structures for preventing contamination.  
     BRIEF SUMMARY OF THE INVENTION  
      According to a first aspect of the present invention, there is provided an immersion exposure apparatus comprising: a substrate holding unit which holds a substrate to be exposed; a projection lens provided above the substrate holding unit to supply exposure light to the substrate held on the substrate holding unit; a liquid supply unit which supplies a liquid to an area between the substrate held on the substrate holding unit and the projection lens; and a structural unit which surrounds the substrate holding unit and which is configured to supply an interposer to an area between the structural unit and the substrate held on the substrate holding unit.  
      According to a second aspect of the present invention, there is provided a method of manufacturing a semiconductor device using the immersion exposure apparatus according to claim  1 , the method comprising: holding the substrate on the substrate holding unit; supplying the interposer from the structural unit to an area between the substrate held on the substrate holding unit and the structural unit; supplying a liquid from the liquid supply unit to an area between the substrate held on the substrate holding unit and the projection lens; and supplying exposure light to the substrate through the projection lens with the liquid interposed between the substrate held on the substrate holding unit and the projection lens. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       FIG. 1  is a diagram schematically showing the general configuration of an immersion exposure apparatus according to an embodiment of the present invention;  
       FIG. 2  is a plan view schematically showing the arrangement of a semiconductor wafer and the like according to the embodiment of the present invention;  
       FIG. 3  is a diagram schematically showing how the immersion exposure apparatus according to the embodiment of the present invention is used;  
       FIG. 4  is a diagram schematically showing a modification of the immersion exposure apparatus according to the embodiment of the present invention;  
       FIG. 5  is a diagram schematically showing another modification of the immersion exposure apparatus according to the embodiment of the present invention;  
       FIG. 6  is a diagram schematically showing still another modification of the immersion exposure apparatus according to the embodiment of the present invention; and  
       FIG. 7  is a flowchart showing a method of manufacturing a semiconductor device using the immersion exposure apparatus according to the embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      An embodiment of the present invention will be described below with reference to the drawings.  
       FIG. 1  is a diagram schematically showing the general configuration of an immersion exposure apparatus according to an embodiment of the present invention.  
      As is the case with conventional immersion exposure apparatuses, a semiconductor wafer (semiconductor substrate)  11  to be exposed is held on a wafer chuck (wafer holding unit)  12 . A projection lens  13  is placed above the wafer chuck  12 . A mask chuck (mask holding unit)  15  is placed above the projection lens  13  to hold a photo mask  14 . The photo mask  14  is irradiated with illumination light from a light source (not shown). A mask pattern on the photo mask  14  is projected on the semiconductor wafer  11  by supplying exposure light having passed through the photo mask  14  to the semiconductor wafer  11  via the projection lens  13 .  
      A liquid supply/recovery unit  16  supplies a liquid  17  for immersion exposure to the area between the semiconductor wafer  11  held on the wafer chuck  12  and the projection lens  13 . The liquid supply/recovery unit  16  does not supply the liquid  17  to the entire principal surface of the semiconductor wafer  11  but to a partial area of the principal surface. The supplied liquid  17  can be recovered by the liquid supply/recovery unit  16 . The liquid  17  is, for example, water. Resolution can be increased by carrying out exposure with the liquid  17  interposed between the semiconductor wafer  11  and the projection lens  13 .  
      The wafer chuck  12  and the mask chuck  15  can each move (scan) relative to the projection lens  13 . Moving the wafer chuck  12  and mask chuck  15  to a desired position for exposure enables the mask pattern formed on the photo mask  14  at a desired position to be projected on the semiconductor wafer  11  at a desired position. The position of the liquid  17  on the semiconductor wafer  11  also varies with the movement of the wafer chuck  12 .  
      A structural unit  21  having a wall like outer shape is placed around the wafer chuck  12 . The structural unit  21  surrounds the wafer chuck  12 . The top surface of the structural unit  21  is higher than that of the semiconductor wafer  11  held on the wafer chuck  12 .  
      The structural unit  21  can supply an interposer  22  to the area between the structural unit  21  and the semiconductor wafer  11 .  FIG. 2  is a plan view schematically showing the positional relationship between the semiconductor wafer  11 , the structural unit  21  and the interposer  22 . The interposer  22  thus interposed between the structural unit  21  and the semiconductor wafer  11  makes it possible to prevent the downward leakage of the liquid  17  flowing out of the semiconductor wafer  11 . For example, as shown in  FIG. 3 , even if the wafer chuck  12  moves to a position where it may cause the liquid  17  to fall from the end of the semiconductor wafer  11 , the interposer  22  interposed between the structural unit  21  and the semiconductor wafer  11  enables the leakage of the liquid  17  to be prevented. This makes it possible to prevent the apparatus from being disadvantageously contaminated with the liquid  17  flowing out of the semiconductor wafer  11 .  
      The interposer  22  is usually not interposed between the structural unit  21  and the semiconductor wafer  11  but is, for example, housed in the structural unit  21 . For immersion exposure, the interposer  22  projects out of the structural unit  21  toward the outer periphery of the semiconductor wafer  11 . The interposer  22  is then placed between the structural unit  21  and the semiconductor  11 . Thus, the interposer  22  is not always fixed and is usually not interposed between the structural unit  21  and the semiconductor wafer  11 . This makes it possible to avoid the problem that when the semiconductor wafer  11  is set on the wafer chuck  12 , the interposer  22  constitutes an obstacle to the setting of the semiconductor wafer  11 .  
      Since the semiconductor wafer  11  moves together with the wafer chuck  12 , the spacing between the structural unit  21  and the semiconductor wafer  11  is not fixed but varies depending on the position as shown in  FIG. 3 . Accordingly, the interposer  22  is controlled so that the projection amount (projection width) of the interposer  22  varies in response to the movement of the wafer chuck  12 .  
      The interposer  22  may be, for example, a deformable flexible material. Specifically, the interposer  22  may be plastic, which maintains a shape resulting from deformation as it is, or elastomer, the shape of which changes from one resulting from deformation back to the original one when an external force is removed. The elastomer may be a thin film in which a gas or liquid is sealed. If a deformable flexible material is used as the interposer  22 , the interposer  22  is deformed depending on the shape of outer periphery of the semiconductor wafer  11 . This allows the interposer  22  to adhere easily to the outer periphery of the semiconductor wafer  11 .  
      Alternatively, the interposer  22  may be a rigid material formed of metal or nonmetal instead of the deformable flexible material. For example, as shown in  FIG. 4 , a plate-like material can be used as the interposer  22 .  
      A washing mechanism may be provided inside the structural unit  21  to wash the interposer  22 . Contaminants such as the liquid for immersion exposure often adhere to the surface of the interposer  22 . The washing mechanism provided inside the structural unit  21  enables the interposer  22  to be effectively washed after the interposer  22  has been housed in the structural unit  21 .  
      In the above embodiment, the interposer  22  is usually housed in the structural unit  21 . However, as shown in  FIG. 5 , a housing container  23  may be provided in addition to the structural unit  21  so that the interposer  22  can be housed in the housing container  23 . In this case, the interposer  22  discharged from the housing container  23  is supplied to the area between the structural unit  21  and the semiconductor wafer  11  via a tube  24  and the structural unit  21 .  
      As shown in  FIG. 6 , a supply container  25  and a recovery container  26  are provided; the supply container  25  supplies the interposer  22  and the recovery container  26  recovers the interposer  22 . In this case, the interposer  22  discharged from the supply container  25  is supplied to the area between the structural unit  21  and the semiconductor wafer  11  via a tube  27  and the structural unit  21 . The interposer  22  interposed between the structural unit  21  and the semiconductor wafer  11  is recovered into the recovery container  26  via the structural unit  21  and a tube  28 . Thus, the separately provided supply container  25  and recovery container  26  make it possible to prevent the used interposer  22  from disadvantageously contaminating the unused interposer  22 .  
      In the above embodiment, the interposer  22  is contacted with the outer periphery of the semiconductor wafer  11 . However, a small gap may be present between the interposer  22  and the semiconductor wafer  11 . In spite of the small gap, surface tension enables the liquid  17  to be held.  
      Now, with reference to the flowchart shown in  FIG. 7 , description will be given of a method for manufacturing a semiconductor device using the above immersion exposure apparatus.  
      First, the semiconductor wafer  11  to be exposed is held on the wafer chuck  12  (S 1 ). Films to be processed (conductive film or insulating film) and a photo resist film are formed on the semiconductor wafer  11 .  
      The structural unit  21  supplies the interposer  22  to the area between the semiconductor wafer  11  held on the wafer chuck  12  and the structural unit  21 . This places the interposer  22  between the semiconductor wafer  11  and the structural unit  21  (S 2 ).  
      Then, the liquid supply/recovery unit  16  supplies the liquid  17  for immersion exposure to the area between the semiconductor wafer  11  held on the wafer chuck  12  and the projection lens  13  (S 3 ). As a result, the liquid  17  is interposed between the semiconductor wafer  11  and the projection lens  13 .  
      Then, exposure is carried out with the liquid  17  interposed between the semiconductor wafer  11  and the projection lens  13  (S 4 ). That is, the mask pattern on the photo mask  14  is projected on the semiconductor wafer  11  via the projection lens  13  and liquid  17 . A latent image corresponding to the mask pattern is formed in the photo resist.  
      Then, a photo resist pattern is formed by development. The films to be processed are etched using the photo resist pattern as a mask to form a processed pattern corresponding to the mask pattern (S 5 ).  
      As described above, the present embodiment interposes the interposer  22  between the semiconductor wafer  11  and the structural unit  21 . This makes it possible to prevent the downward leakage of the liquid  17  for immersion exposure. Therefore, the apparatus can be prevented from being contaminated with the liquid  17 .  
      The interposer  22  is supplied by the structural unit  21  and is not always present between the semiconductor wafer  11  and the structural unit  21 . This makes it possible to avoid the problem that when the semiconductor wafer  11  is set on the wafer chuck  12 , the interposer  22  constitutes an obstacle to the setting of the semiconductor wafer. Therefore, the semiconductor wafer  11  can be easily and steadily set on the wafer chuck  12 . Further, since the interposer  22  is not always present between the semiconductor wafer  11  and the structural unit  21 , it can be easily washed.  
      As a result, the productivity and yield of semiconductor devices can be improved by using the immersion exposure apparatus according to the present embodiment to manufacture semiconductor devices.  
      Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.