Patent Publication Number: US-2009227111-A1

Title: Barrier film material and pattern formation method using the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of U.S. application Ser. No. 11/058,369, filed Feb. 16, 2005, which claims priority under 35 U.S.C. §119 on Patent Application No. 2004-49323 filed in Japan on Feb. 25, 2004, and Patent Application No. 2004-361058 filed in Japan on Dec. 14, 2004, the entire contents of which are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a material for a barrier film formed on a resist film for use in fabrication process or the like for semiconductor devices and a pattern formation method using the same. 
     In accordance with the increased degree of integration of semiconductor integrated circuits and downsizing of semiconductor devices, there are increasing demands for further rapid development of lithography technique. Currently, pattern formation is carried out through photolithography using exposing light of a mercury lamp, KrF excimer laser, ArF excimer laser or the like, and use of F 2  laser lasing at a shorter wavelength is being examined. However, since there remain a large number of problems in exposure systems and resist materials, photolithography using exposing light of a shorter wavelength has not been put to practical use. 
     In these circumstances, immersion lithography has been recently proposed for realizing further refinement of patterns by using conventional exposing light (for example, see M. Switkes and M. Rothschild, “Immersion lithography at 157 nm”, J. Vac. Sci. Technol., Vol. B19, p. 2353 (2001)). 
     In the immersion lithography, a region in an exposure system sandwiched between a projection lens and a resist film formed on a wafer is filled with a liquid having a refractive index n and therefore, the NA (numerical aperture) of the exposure system has a value n·NA. As a result, the resolution of the resist film can be improved. 
     Now, a conventional pattern formation method employing the immersion lithography will be described with reference to  FIGS. 20A through 20D . 
     First, a positive chemically amplified resist material having the following composition is prepared: 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                 Base polymer: poly((norbornene-5-methylene-t-butyl- 
                 2 
                 g 
               
               
                 carboxylate) (50 mol %) - (maleic anhydride) (50 mol %)) 
               
               
                 Acid generator: triphenylsulfonium triflate 
                 0.06 
                 g 
               
               
                 Quencher: triethanolamine 
                 0.002 
                 g 
               
               
                 Solvent: propylene glycol monomethyl ether acetate 
                 20 
                 g 
               
               
                   
               
            
           
         
       
     
     Next, as shown in  FIG. 20A , the aforementioned chemically amplified resist material is applied on a substrate  1  so as to form a resist film  2  with a thickness of 0.35 μm. 
     Then, as shown in  FIG. 20B , with an immersion liquid (water)  3  provided on the resist film  2 , pattern exposure is carried out by irradiating the resist film  2  with exposing light  4  of ArF excimer laser with NA of 0.68 through a mask  5 . 
     After the pattern exposure, as shown in  FIG. 20C , the resist film  2  is baked with a hot plate at a temperature of 105° C. for 60 seconds, and the resultant resist film is developed with a 2.38 wt % tetramethylammonium hydroxide aqueous solution (alkaline developer). In this manner, a resist pattern  2   a  made of an unexposed portion of the resist film  2  and having a line width of 0.09 μm is formed as shown in  FIG. 20D . 
     SUMMARY OF THE INVENTION 
     As shown in  FIG. 20D , however, the resist pattern  2   a  formed by the conventional pattern formation method is in a defective shape. 
     The present inventors have variously examined the reason why the resist pattern formed by the conventional immersion lithography is in a defective shape, resulting in finding the following: The resist film cannot exhibit its expected performance because a low-molecular-weight compound such as the acid generator or the quencher is eluted from the resist film  2  into the liquid  3  provided on the resist film  2  or because the liquid  3  permeates into the resist film  2 . For example, in the case shown in  FIG. 20D , the resist pattern  2   a  is in a defective shape with a T-top shaped portion probably because the concentration of an acid generated from the acid generator is lowered on the interface between an exposed portion and the unexposed portion of the resist film  2 . On the contrary, when the concentration of the quencher used for deactivating the acid is lowered, the resultant resist pattern  2   a  is in a defective shape with round shoulders. 
     In either case, when the resist pattern  2   a  in such a defective shape is used for etching a target film, the resultant pattern of the target film is also in a defective shape, which disadvantageously lowers the productivity and the yield in the fabrication process for semiconductor devices. 
     In consideration of the aforementioned conventional problem, an object of the invention is forming a fine resist pattern in a good shape by preventing the influence of an immersion liquid used in the immersion lithography on a resist film. 
     The present inventors have found, on the basis of the aforementioned result of the examination, that a component of a resist film can be prevented from eluting into a liquid or a liquid can be prevented from permeating into a resist film by forming a barrier film on the resist film so as not to allow the resist film to be in direct contact with the liquid provided thereon. Furthermore, the barrier film formed on the resist film has such a composition that its solubility is changed in accordance with the value of hydrogen ion exponent (pH), so that the barrier film can be insoluble in the liquid but soluble in a developer. 
     The present invention was devised on the basis of the aforementioned findings, and according to the invention, a barrier film for preventing a component of a resist film from eluting into a liquid or for preventing a liquid from permeating into a resist film is formed on the resist film, so that the resist film can keep its expected performance. Specifically, the present invention is practiced as follows: 
     The barrier film material of this invention is a material for a barrier film formed between a resist film made of a chemically amplified resist and a liquid in performing exposure with the liquid provided above the resist film, and the barrier film prevents a component of the resist film from eluting into the liquid or prevents the liquid from permeating into the resist film. 
     According to this invention, in immersion lithography in which a resist film made of a chemically amplified resist is exposed with a liquid provided on the resist film, the barrier film made of the barrier film material and formed between the resist film and the liquid prevents a component, such as an acid generator or a quencher, of the resist film from eluting into the liquid or prevents the liquid from permeating into the resist film. Therefore, the resist film keeps the expected performance of the chemically amplified resist through the exposure. As a result, a resist pattern can be formed in a good shape. 
     In the barrier film material of the invention, the barrier film preferably has solubility different depending upon a value of hydrogen ion exponent (pH). Furthermore, the barrier film is preferably soluble in a solution with a value of hydrogen ion exponent (pH) larger than 7. In other words, when the barrier film has a composition, for example, that is insoluble in the liquid but soluble in an alkaline developer, the barrier film does not dissolve in the liquid during the exposure but can be easily removed after the exposure. 
     The barrier film material of the invention can include an alkali-soluble polymer and a fluorine-based surface active agent. Since a fluorine-based surface active agent has a higher hydrophobic property than a surface active agent not including fluorine, when the barrier film is made of an alkali-soluble polymer including a fluorine-based surface active agent, even if a liquid is provided on the barrier film, the barrier film does not dissolve in the liquid. Accordingly, the barrier film of the invention can prevent contact between the resist film and the liquid, and hence, it can prevent a component of the resist film from eluting into the liquid or prevent the liquid from permeating into the resist film. A sufficient effect can be attained when the content of the fluorine-based surface active agent in the alkali-soluble polymer is approximately 1/100 wt % through 1/10 wt %, which does not limit the invention, and the content may be smaller or larger. 
     In a known technique, an antireflection film for preventing reflection of exposing light is formed on a resist film. A surface active agent is sometimes included in the antireflection film, but the concentration of the surface active agent in the antireflection film is smaller than the content of the fluorine-based surface active agent in the alkali-soluble polymer of this invention by one or more figures. This is because the surface active agent is included in the antireflection film for the purpose of improving the application property of the antireflection film. In addition, the antireflection film is water-soluble, and hence, when a large amount of surface active agent is included in the antireflection film, the hydrophobic property of the antireflection film is so high that it may not be dissolved in water. In contrast, the barrier film of this invention is insoluble in a neutral or acidic solution. 
     The alkali-soluble polymer included in the barrier film material of this invention can be at least one of polyvinyl hexafluoroisopropyl alcohol, polyvinyl alcohol, polyacrylic acid, polystyrenesulfonic acid, hydroxyethyl cellulose, polyisoplenesulfonic acid, polyvinyl pyrrolidone and pullulan. 
     Furthermore, the fluorine-based surface active agent may have a group with a double bond. Also, the group with a double bond may be a perfluoroalkenyl group. 
     The perfluoroalkenyl group may be a 1,1-di(perfluoromethyl)-2-perfluoroethylethenyl group or a 1,1-di(perfluoroisopropyl)-2-perfluoromethylethenyl group. 
     Moreover, the fluorine-based surface active agent having the 1,1-di(perfluoromethyl)-2-perfluoroethylethenyl group may be 1,1-di(perfluoromethyl)-2-perfluoroethylethenyloxybenzyltrimethylammonium or 1,1-di(perfluoromethyl)-2-perfluoroethylethenylpolyoxyethylene ether. 
     Alternatively, the fluorine-based surface active agent having the 1,1-di(perfluoroisopropyl)-2-perfluoromethylethenyl group may be 1,1-di(perfluoroisopropyl)-2-perfluoromethylethenyloxybenzyltrimethylammonium or 1,1-di(perfluoroisopropyl)-2-perfluoromethylethenylpolyoxyethylene ether. 
     Furthermore, the present inventors have found that when a polymer having a sulfonamide structure is used as the barrier film material, a resultant barrier film including the polymer having the sulfonamide structure can prevent the contact between the liquid and the resist film. 
     The polymer having a sulfonamide structure is soluble in a solution with a value of hydrogen ion exponent (pH) larger than 7 while it is insoluble in a neutral or acidic solution. Accordingly, it is not dissolved in a neutral or acidic solution generally having a value of pH of 7 or less and is soluble in an alkaline aqueous solution used as a developer, and hence, it can be easily removed after the exposure. 
     The barrier film of this invention preferably includes a polymer having a sulfonamide structure. 
     In this case, the polymer may be polyvinylsulfonamide or a polyvinylsulfonamide derivative. The polyvinylsulfonamide derivative may be polyvinylsulfone alkylamide, polyvinylsulfone alkylamide fluoride or polyvinylsulfone substituted alkylamide. 
     Also, a substituent group of the polyvinylsulfone substituted alkylamide may be a hydroxyl group, an alkoxy group, an oxo group, an amino group or an alkylamino group. 
     The first pattern formation method using the barrier film material of this invention includes the steps of forming a resist film made of a chemically amplified resist on a substrate; forming a barrier film on the resist film; performing pattern exposure by selectively irradiating the resist film with exposing light with a liquid provided on the barrier film; removing the barrier film; and forming a resist pattern made of the resist film by developing the resist film after removing the barrier film, and the barrier film prevents a component of the resist film from eluting into the liquid or prevents the liquid from permeating into the resist film. 
     In the first pattern formation method, the barrier film formed on the resist film prevents a component of the resist film from eluting into the liquid or prevents the liquid from permeating into the resist film, and therefore, the resist film keeps the expected performance of the chemically amplified resist during the pattern exposure. As a result, the resist pattern made of the resist film can be formed in a good shape. In this case, the barrier film can be removed before the development with an aqueous solution having a pH value for dissolving the barrier film, and examples of such a solution are a developer and a diluted developer. The diluted developer is diluted to an extent of a concentration lower than a general alkaline developer (i.e., 2.38 wt % tetramethylammonium hydroxide), and the concentration is, for example, approximately 0.001 wt % through 2 wt %, whereas the concentration does not limit the invention. 
     The second pattern formation method using the barrier film material of this invention includes the steps of forming a resist film made of a chemically amplified resist on a substrate; forming a barrier film on the resist film; performing pattern exposure by selectively irradiating the resist film with exposing light with a liquid provided on the barrier film; and removing the barrier film and forming a resist pattern made of the resist film by developing the resist film after the pattern exposure, and the barrier film prevents a component of the resist film from eluting into the liquid or prevents the liquid from permeating into the resist film. 
     In the second pattern formation method, the barrier film formed on the resist film prevents a component of the resist film from eluting into the liquid or prevents the liquid from permeating into the resist film in the same manner as in the first pattern formation method, and therefore, the resist film keeps the expected performance of the chemically amplified resist during the pattern exposure. As a result, the resist pattern made of the resist film can be formed in a good shape. 
     A difference between the first pattern formation method and the second pattern formation method is that the barrier film formed on the resist film is removed before the development in the first pattern formation method while it is removed during the development with a developer in the second pattern formation method. In the case of the first pattern formation method, since the barrier film is removed before the development, the development processing is generally proceeded. Alternatively, in the case of the second pattern formation method, since the barrier film is removed during the development, the dissolution characteristic of the resist can be controlled, resulting in improving the dissolution characteristic of the resist. The control of the dissolution characteristic will be described later. 
     The first or second pattern formation method preferably further includes, before the step of performing pattern exposure, a step of annealing the barrier film. When the barrier film is thus annealed, the denseness of the barrier film is improved and hence its insoluble property in the liquid is improved. It is noted that the barrier film should be annealed at a temperature of an appropriate range because the barrier film is difficult to remove by dissolving it if its denseness is excessively improved. The appropriate range of the annealing temperature depends upon the composition of the barrier film and is, for example, approximately 100° C. through 150° C., which does not limit the invention. 
     In the first or second pattern formation method, the barrier film preferably has solubility different depending upon a value of hydrogen ion exponent (pH). When the barrier film has such a composition that it is insoluble in the liquid but is soluble in an alkaline developer, the barrier film can be easily and definitely removed after the pattern exposure. 
     In the first or second pattern formation method, the barrier film preferably includes an alkali-soluble polymer and a fluorine-based surface active agent. Specifically, the compounds described with respect to the barrier film material of this invention may be used as the alkali-soluble polymer and the fluorine-based surface active agent. 
     In the first or second pattern formation method, the barrier film preferably includes a polymer having a sulfonamide structure. Specifically, the compounds described with respect to the barrier film material of this invention may be used as the polymer having a sulfonamide structure. 
     In the first or second pattern formation method, the liquid may be water or perfluoropolyether. Also, the liquid may include an additive such as a surface active agent. 
     Alternatively, in the first or second pattern formation method, the liquid may be an acidic solution. Examples of the acidic solution are a phosphoric acid aqueous solution and a cesium sulfate aqueous solution, which does not limit the invention. 
     In the first or second pattern formation method, the exposing light may be KrF excimer laser, ArF excimer laser, F 2  laser, ArKr laser or Ar 2  laser. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A ,  1 B,  1 C and  1 D are cross-sectional views for showing procedures in a pattern formation method using a barrier film material according to Embodiment 1 of the invention; 
         FIGS. 2A and 2B  are cross-sectional views for showing other procedures in the pattern formation method using the barrier film material of Embodiment 1; 
         FIGS. 3A ,  3 B,  3 C and  3 D are cross-sectional views for showing procedures in a pattern formation method using a barrier film material according to Embodiment 2 of the invention; 
         FIGS. 4A ,  4 B and  4 C are cross-sectional views for showing other procedures in the pattern formation method using the barrier film material of Embodiment 2; 
         FIGS. 5A ,  5 B,  5 C and  5 D are cross-sectional views for showing procedures in a pattern formation method using a barrier film material according to Embodiment 3 of the invention; 
         FIG. 6  is a cross-sectional view for showing another procedure in the pattern formation method using the barrier film material of Embodiment 3; 
         FIG. 7  is a graph for explaining control of solubility of a resist in the pattern formation method using the barrier film material of Embodiment 3; 
         FIGS. 8A ,  8 B,  8 C and  8 D are cross-sectional views for showing procedures in a pattern formation method using a barrier film material according to Embodiment 4 of the invention; 
         FIGS. 9A and 9B  are cross-sectional views for showing other procedures in the pattern formation method using the barrier film material of Embodiment 4; 
         FIGS. 10A ,  10 B,  10 C and  10 D are cross-sectional views for showing procedures in a pattern formation method using a barrier film material according to Embodiment 5 of the invention; 
         FIGS. 11A and 11B  are cross-sectional views for showing other procedures in the pattern formation method using the barrier film material of Embodiment 5; 
         FIGS. 12A ,  12 B,  12 C and  12 D are cross-sectional views for showing procedures in a pattern formation method using a barrier film material according to Embodiment 6 of the invention; 
         FIGS. 13A and 13B  are cross-sectional views for showing other procedures in the pattern formation method using the barrier film material of Embodiment 6; 
         FIGS. 14A ,  14 B,  14 C and  14 D are cross-sectional views for showing procedures in a pattern formation method using a barrier film material according to Embodiment 7 of the invention; 
         FIGS. 15A ,  15 B and  15 C are cross-sectional views for showing other procedures in the pattern formation method using the barrier film material of Embodiment 7; 
         FIGS. 16A ,  16 B,  16 C and  16 D are cross-sectional views for showing procedures in a pattern formation method using a barrier film material according to Embodiment 8 of the invention; 
         FIG. 17  is a cross-sectional view for showing another procedure in the pattern formation method using the barrier film material of Embodiment 8; 
         FIGS. 18A ,  18 B,  18 C and  18 D are cross-sectional views for showing procedures in a pattern formation method using a barrier film material according to Embodiment 9 of the invention; 
         FIGS. 19A and 19B  are cross-sectional views for showing other procedures in the pattern formation method using the barrier film material of Embodiment 9; and 
         FIGS. 20A ,  20 B,  20 C and  20 D are cross-sectional views for showing procedures in a conventional pattern formation method employing immersion lithography. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiment 1 
     A pattern formation method using a barrier film material according to Embodiment 1 of the invention will now be described with reference to  FIGS. 1A through 1D ,  2 A and  2 B. 
     First, a positive chemically amplified resist material having the following composition is prepared: 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                 Base polymer: poly((norbornene-5-methylene-t-butyl- 
                 2 
                 g 
               
               
                 carboxylate) (50 mol %) - (maleic anhydride) (50 mol %)) 
               
               
                 Acid generator: triphenylsulfonium triflate 
                 0.06 
                 g 
               
               
                 Quencher: triethanolamine 
                 0.002 
                 g 
               
               
                 Solvent: propylene glycol monomethyl ether acetate 
                 20 
                 g 
               
               
                   
               
            
           
         
       
     
     Next, as shown in  FIG. 1A , the aforementioned chemically amplified resist material is applied on a substrate  101  so as to form a resist film  102  with a thickness of 0.35 μm. 
     Then, as shown in  FIG. 1B , a barrier film  103  that is made of a barrier film material having the following composition, has a thickness of 0.06 μm and is different in its solubility depending upon the value of pH is formed on the resist film  102  by, for example, spin coating: 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                 Alkali-soluble polymer: polyvinyl alcohol 
                 1 
                 g 
               
               
                 Fluorine-based surface active agent: 1,1-di(perfluoro- 
                 0.0003 
                 g 
               
               
                 methyl)-2-perfluoroethylethenyloxybenzyltrimethyl- 
               
               
                 ammonium 
               
               
                 Solvent: isobutyl alcohol 
                 20 
                 g 
               
               
                   
               
            
           
         
       
     
     Next, as shown in  FIG. 1C , with an immersion liquid  104  of water provided between the barrier film  103  and a projection lens  106  by, for example, a puddle method, pattern exposure is carried out by irradiating the resist film  102  through the barrier film  103  with exposing light  105  of ArF excimer laser with NA of 0.68 having passed through a mask (not shown). 
     After the pattern exposure, as shown in  FIG. 1D , the resist film  102  is baked with a hot plate at a temperature of 105° C. for 60 seconds (post exposure bake). 
     Next, as shown in  FIG. 2A , the barrier film  103  is removed with, for example, a 0.01 wt % tetramethylammonium hydroxide aqueous solution (diluted alkaline developer). Thereafter, the resultant resist film  102  is developed with a 2.38 wt % tetramethylammonium hydroxide aqueous solution (alkaline developer). In this manner, a resist pattern  102   a  made of an unexposed portion of the resist film  102  and having a line width of 0.09 μm is formed in a good shape as shown in  FIG. 2B . 
     In this manner, according to Embodiment 1, before carrying out the pattern exposure shown in  FIG. 1C , the barrier film  103  including the alkali-soluble polymer and the fluorine-based surface active agent is formed on the resist film  102 . Therefore, the resist film  102  is never in direct contact with the immersion liquid  104 . Accordingly, a component of the resist film  102  such as the acid generator or the quencher can be prevented from eluting into the immersion liquid  104  or the immersion liquid  104  can be prevented from permeating into the resist film  102  on the contrary, and hence, the resist film  102  keeps the expected performance of the chemically amplified resist through the exposure and the post exposure bake performed thereafter. As a result, the resist pattern  102   a  made of the resist film  102  is not degraded in its shape. 
     Embodiment 2 
     A pattern formation method using a barrier film material according to Embodiment 2 of the invention will now be described with reference to  FIGS. 3A through 3D  and  4 A through  4 C. 
     First, a positive chemically amplified resist material having the following composition is prepared: 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                 Base polymer: poly((norbornene-5-methylene-t-butyl- 
                 2 
                 g 
               
               
                 carboxylate) (50 mol %) - (maleic anhydride) (50 mol %)) 
               
               
                 Acid generator: triphenylsulfonium triflate 
                 0.06 
                 g 
               
               
                 Quencher: triethanolamine 
                 0.002 
                 g 
               
               
                 Solvent: propylene glycol monomethyl ether acetate 
                 20 
                 g 
               
               
                   
               
            
           
         
       
     
     Next, as shown in  FIG. 3A , the aforementioned chemically amplified resist material is applied on a substrate  201  so as to form a resist film  202  with a thickness of 0.35 μm. 
     Then, as shown in  FIG. 3B , a barrier film  203  that is made of a barrier film material having the following composition, has a thickness of 0.07 μm and is different in its solubility depending upon the value of pH is formed on the resist film  202  by, for example, the spin coating: 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                 Alkali-soluble polymer: polyvinyl pyrrolidone 
                 1 
                 g 
               
               
                 Fluorine-based surface active agent: 1,1-di(perfluoro- 
                 0.0005 
                 g 
               
               
                 isopropyl)-2-perfluoromethylethenyloxybenzyltrimethyl- 
               
               
                 ammonium 
               
               
                 Solvent: n-butyl alcohol 
                 20 
                 g 
               
               
                   
               
            
           
         
       
     
     Next, as shown in  FIG. 3C , the barrier film  203  is annealed with a hot plate at a temperature of 120° C. for 90 seconds, so as to improve the denseness of the barrier film  203 . 
     After the annealing, as shown in  FIG. 3D , with an immersion liquid  204  of water provided between the barrier film  203  and a projection lens  206  by, for example, the puddle method, pattern exposure is carried out by irradiating the resist film  202  through the barrier film  203  with exposing light  205  of ArF excimer laser with NA of 0.68 having passed through a mask (not shown). 
     After the pattern exposure, as shown in  FIG. 4A , the resist film  202  is baked with a hot plate at a temperature of 105° C. for 60 seconds (post exposure bake). 
     Next, as shown in  FIG. 4B , the barrier film  203  is removed with, for example, a 0.005 wt % tetramethylammonium hydroxide aqueous solution (diluted alkaline developer). Thereafter, the resultant resist film  202  is developed with a 2.38 wt % tetramethylammonium hydroxide aqueous solution (alkaline developer). In this manner, a resist pattern  202   a  made of an unexposed portion of the resist film  202  and having a line width of 0.09 μm is formed in a good shape as shown in  FIG. 4C . 
     In this manner, according to Embodiment 2, before carrying out the pattern exposure shown in  FIG. 3D , the barrier film  203  including the alkali-soluble polymer and the fluorine-based surface active agent is formed on the resist film  202 . Therefore, the resist film  202  is never in direct contact with the immersion liquid  204 . Accordingly, a component of the resist film  202  such as the acid generator or the quencher can be prevented from eluting into the immersion liquid  204  or the immersion liquid  204  can be prevented from permeating into the resist film  202  on the contrary, and hence, the resist film  202  keeps the expected performance of the chemically amplified resist through the exposure and the post exposure bake performed thereafter. As a result, the resist pattern  202   a  made of the resist film  202  is not degraded in its shape. 
     In addition, in Embodiment 2, since the barrier film  203  is annealed for improving the denseness as shown in  FIG. 3C  before the pattern exposure, the insolubility of the barrier film  203  in the immersion liquid  204  (water) is increased. Therefore, the function of the barrier film  203  as a barrier for preventing the acid generator or the like from eluting from the resist film  202  into the immersion liquid  204  can be improved. 
     Embodiment 3 
     A pattern formation method using a barrier film material according to Embodiment 3 of the invention will now be described with reference to  FIGS. 5A  through  5 D and  6 . 
     First, a positive chemically amplified resist material having the following composition is prepared: 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                 Base polymer: poly((norbornene-5-methylene-t-butyl- 
                 2 
                 g 
               
               
                 carboxylate) (50 mol %) - (maleic anhydride) (50 mol %)) 
               
               
                 Acid generator: triphenylsulfonium triflate 
                 0.06 
                 g 
               
               
                 Quencher: triethanolamine 
                 0.002 
                 g 
               
               
                 Solvent: propylene glycol monomethyl ether acetate 
                 20 
                 g 
               
               
                   
               
            
           
         
       
     
     Next, as shown in  FIG. 5A , the aforementioned chemically amplified resist material is applied on a substrate  301  so as to form a resist film  302  with a thickness of 0.35 μm. 
     Then, as shown in  FIG. 5B , a barrier film  303  that is made of a barrier film material having the following composition, has a thickness of 0.05 μm and is different in its solubility depending upon the value of pH is formed on the resist film  302  by, for example, the spin coating: 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                 Alkali-soluble polymer: polyacrylic acid 
                 1 
                 g 
               
               
                 Fluorine-based surface active agent: 1,1-di(perfluoro- 
                 0.0006 
                 g 
               
               
                 methyl)-2-perfluoroethylethenylpolyoxyethylene ether 
               
               
                 Solvent: n-butyl alcohol 
                 20 
                 g 
               
               
                   
               
            
           
         
       
     
     Next, as shown in  FIG. 5C , with an immersion liquid  304  of water provided between the barrier film  303  and a projection lens  306  by, for example, the puddle method, pattern exposure is carried out by irradiating the resist film  302  through the barrier film  303  with exposing light  305  of ArF excimer laser with NA of 0.68 having passed through a mask (not shown). 
     After the pattern exposure, as shown in  FIG. 5D , the resist film  302  is baked with a hot plate at a temperature of 105° C. for 60 seconds (post exposure bake). 
     Next, the barrier film  303  is removed and the resultant resist film  302  is developed with a 2.38 wt % tetramethylammonium hydroxide aqueous solution (alkaline developer). In this manner, a resist pattern  302   a  made of an unexposed portion of the resist film  302  and having a line width of 0.09 μm is formed in a good shape as shown in  FIG. 6 . 
     In this manner, according to Embodiment 3, before carrying out the pattern exposure shown in  FIG. 5C , the barrier film  303  including the alkali-soluble polymer and the fluorine-based surface active agent is formed on the resist film  302 . Therefore, the resist film  302  is never in direct contact with the immersion liquid  304 . Accordingly, a component of the resist film  302  such as the acid generator or the quencher can be prevented from eluting into the immersion liquid  304  or the immersion liquid  304  can be prevented from permeating into the resist film  302  on the contrary, and hence, the resist film  302  keeps the expected performance of the chemically amplified resist through the exposure and the post exposure bake performed thereafter. As a result, the resist pattern  302   a  made of the resist film  302  is not degraded in its shape. 
     In the pattern formation method of Embodiment 3, the barrier film  303  is removed during the development, namely, with the alkaline developer, differently from those of Embodiments 1 and 2. Thus, the dissolution characteristic of the resist film  302  can be controlled. The control of the dissolution characteristic will now be described with reference to  FIG. 7 . 
     In general, when the dissolution characteristic of a resist in a developer is high, the dissolution rate is abruptly increased when exposure exceeds a given threshold value as shown with a graph A of a broken line in  FIG. 7 . As the change of the dissolution rate against the exposure is more abrupt, a difference in the solubility between an exposed portion and an unexposed portion of the resist film  302  is larger, and hence, higher resolution can be attained, namely, the resist pattern  302   a  can be formed in a better shape. Accordingly, in the case where the barrier film  303  is removed simultaneously with the development, the dissolution rate is wholly lowered during the removal of the barrier film  303  as shown with a graph B of a solid line in  FIG. 7 , and hence, the change in a portion surrounded with a circle C in the graph B can be reduced to be approximated to a flat portion of the graph A. As a result, in the case where the actual resist has the dissolution characteristic as shown with the graph B, the dissolution rate attained with smaller exposure can be adjusted to attain a comparatively constant state with small exposure and a low dissolution rate within a given range. Accordingly, the difference in the solubility between an exposed portion and an unexposed portion of the resist film  302  can be substantially increased, resulting in easily forming a resist pattern in a good shape. 
     Embodiment 4 
     A pattern formation method using a barrier film material according to Embodiment 4 of the invention will now be described with reference to  FIGS. 8A through 8D ,  9 A and  9 B. 
     First, a positive chemically amplified resist material having the following composition is prepared: 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                 Base polymer: poly((norbornene-5-methylene-t-butyl- 
                 2 
                 g 
               
               
                 carboxylate) (50 mol %) - (maleic anhydride) (50 mol %)) 
               
               
                 Acid generator: triphenylsulfonium triflate 
                 0.06 
                 g 
               
               
                 Quencher: triethanolamine 
                 0.002 
                 g 
               
               
                 Solvent: propylene glycol monomethyl ether acetate 
                 20 
                 g 
               
               
                   
               
            
           
         
       
     
     Next, as shown in  FIG. 8A , the aforementioned chemically amplified resist material is applied on a substrate  401  so as to form a resist film  402  with a thickness of 0.35 μm. 
     Then, as shown in  FIG. 8B , a barrier film  403  that is made of a barrier film material having the following composition, has a thickness of 0.04 μm and is different in its solubility depending upon the value of pH is formed on the resist film  402  by, for example, the spin coating: 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                 Alkali-soluble polymer: polyvinyl hexafluoroisopropyl 
                 1 
                 g 
               
               
                 alcohol 
               
               
                 Fluorine-based surface active agent: 1,1-di(perfluoro- 
                 0.0005 
                 g 
               
               
                 isopropyl)-2-perfluoromethylethenylpolyoxyethylene ether 
               
               
                 Solvent: isobutyl alcohol 
                 20 
                 g 
               
               
                   
               
            
           
         
       
     
     Next, as shown in  FIG. 8C , the barrier film  403  is annealed with a hot plate at a temperature of 115° C. for 90 seconds, so as to improve the denseness of the barrier film  403 . 
     After the annealing, as shown in  FIG. 8D , with an immersion liquid  404  of water provided between the barrier film  403  and a projection lens  406  by, for example, the puddle method, pattern exposure is carried out by irradiating the resist film  402  through the barrier film  403  with exposing light  405  of ArF excimer laser with NA of 0.68 having passed through a mask (not shown). 
     After the pattern exposure, as shown in  FIG. 9A , the resist film  402  is baked with a hot plate at a temperature of 105° C. for 60 seconds (post exposure bake). 
     Next, the barrier film  403  is removed and the resultant resist film  402  is developed with a 2.38 wt % tetramethylammonium hydroxide aqueous solution (alkaline developer). In this manner, a resist pattern  402   a  made of an unexposed portion of the resist film  402  and having a line width of 0.09 μm is formed in a good shape as shown in  FIG. 9B . 
     In this manner, according to Embodiment 4, before carrying out the pattern exposure shown in  FIG. 8D , the barrier film  403  including the alkali-soluble polymer and the fluorine-based surface active agent is formed on the resist film  402 . Therefore, the resist film  402  is never in direct contact with the immersion liquid  404 . Accordingly, a component of the resist film  402  such as the acid generator or the quencher can be prevented from eluting into the immersion liquid  404  or the immersion liquid  404  can be prevented from permeating into the resist film  402  on the contrary, and hence, the resist film  402  keeps the expected performance of the chemically amplified resist through the exposure and the post exposure bake performed thereafter. As a result, the resist pattern  402   a  made of the resist film  402  is not degraded in its shape. 
     In addition, in Embodiment 4, since the barrier film  403  is annealed for improving the denseness as shown in  FIG. 8C  before the pattern exposure, the insolubility of the barrier film  403  in the immersion liquid  404  (water) is increased. Therefore, the function of the barrier film  403  as a barrier for preventing the acid generator or the like from eluting from the resist film  402  into the immersion liquid  404  can be improved. 
     Also, since the barrier film  403  is removed during the development, namely, with the alkaline developer, in the same manner as in Embodiment 3, the dissolution characteristic of the resist film  402  can be controlled. 
     Embodiment 5 
     A pattern formation method using a barrier film material according to Embodiment 5 of the invention will now be described with reference to  FIGS. 10A through 10D ,  11 A and  11 B. 
     First, a positive chemically amplified resist material having the following composition is prepared: 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                 Base polymer: poly((styrenehexafluoroisopropyl alcohol) 
                 2 
                 g 
               
               
                 (40 mol %) - (α-trifluoromethyl-t-butylacrylate) 
               
               
                 (60 mol %)) 
               
               
                 Acid generator: triphenylsulfonium triflate 
                 0.06 
                 g 
               
               
                 Quencher: triethanolamine 
                 0.003 
                 g 
               
               
                 Solvent: propylene glycol monomethyl ether acetate 
                 20 
                 g 
               
               
                   
               
            
           
         
       
     
     Next, as shown in  FIG. 1A , the aforementioned chemically amplified resist material is applied on a substrate  501  so as to form a resist film  502  with a thickness of 0.15 μm. 
     Then, as shown in  FIG. 10B , a barrier film  503  that is made of a barrier film material having the following composition, has a thickness of 0.03 μm and is different in its solubility depending upon the value of pH is formed on the resist film  502  by, for example, the spin coating: 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                 Alkali-soluble polymer: polyvinyl alcohol 
                 1 
                 g 
               
               
                 Fluorine-based surface active agent: 1,1-di(perfluoro- 
                 0.0003 
                 g 
               
               
                 methyl)-2-perfluoroethylethenyloxybenzyltrimethyl- 
               
               
                 ammonium 
               
               
                 Solvent: isoamyl alcohol 
                 20 
                 g 
               
               
                   
               
            
           
         
       
     
     Next, as shown in  FIG. 10C , with an immersion liquid  504  of perfluoropolyether provided between the barrier film  503  and a projection lens  506  by, for example, the puddle method, pattern exposure is carried out by irradiating the resist film  502  through the barrier film  503  with exposing light  505  of F 2  laser with NA of 0.85 having passed through a mask (not shown). 
     After the pattern exposure, as shown in  FIG. 10D , the resist film  502  is baked with a hot plate at a temperature of 110° C. for 60 seconds (post exposure bake). 
     Next, as shown in  FIG. 11A , the barrier film  503  is removed with, for example, a 0.01 wt % tetramethylammonium hydroxide aqueous solution (diluted alkaline developer) and thereafter, the resultant resist film  502  is developed with a 2.38 wt % tetramethylammonium hydroxide aqueous solution (alkaline developer). In this manner, a resist pattern  502   a  made of an unexposed portion of the resist film  502  and having a line width of 0.07 μm is formed in a good shape as shown in  FIG. 11B . 
     In this manner, according to Embodiment 5, before carrying out the pattern exposure shown in  FIG. 10C , the barrier film  503  including the alkali-soluble polymer and the fluorine-based surface active agent is formed on the resist film  502 . Therefore, the resist film  502  is never in direct contact with the immersion liquid  504 . Accordingly, a component of the resist film  502  such as the acid generator or the quencher can be prevented from eluting into the immersion liquid  504  or the immersion liquid  504  can be prevented from permeating into the resist film  502  on the contrary, and hence, the resist film  502  keeps the expected performance of the chemically amplified resist through the exposure and the post exposure bake performed thereafter. As a result, the resist pattern  502   a  made of the resist film  502  is not degraded in its shape. 
     Also in Embodiment 5, the annealing for improving the denseness may be performed on the barrier film  503  before the pattern exposure. 
     Also, in the same manner as in Embodiments 3 and 4, the barrier film  503  may be removed not before the development but during the development. 
     In each of Embodiments 1 through 5, the alkali-soluble polymer included in the barrier film is polyvinyl hexafluoroisopropyl alcohol, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylic acid or polystyrenesulfonic acid, and apart from these polymers, hydroxyethyl cellulose, polyisoprenesulfonic acid or pullulan may be used. 
     Furthermore, the fluorine-based surface active agent included in the barrier film is not limited to those used in Embodiments 1 through 5 but may be a surface active agent having a group with a double bond, such as a surface active agent having a perfluoroalkenyl group. 
     Embodiment 6 
     A pattern formation method using a barrier film material according to Embodiment 6 of the invention will now be described with reference to  FIGS. 12A through 12D ,  13 A and  13 B. 
     First, a positive chemically amplified resist material having the following composition is prepared: 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                 Base polymer: poly((norbornene-5-methylene-t-butyl- 
                 2 
                 g 
               
               
                 carboxylate) (50 mol %) - (maleic anhydride) (50 mol %)) 
               
               
                 Acid generator: triphenylsulfonium triflate 
                 0.06 
                 g 
               
               
                 Quencher: triethanolamine 
                 0.002 
                 g 
               
               
                 Solvent: propylene glycol monomethyl ether acetate 
                 20 
                 g 
               
               
                   
               
            
           
         
       
     
     Next, as shown in  FIG. 12A , the aforementioned chemically amplified resist material is applied on a substrate  601  so as to form a resist film  602  with a thickness of 0.35 μm. 
     Then, as shown in  FIG. 12B , a barrier film  603  that is made of a barrier film material having the following composition, has a thickness of 0.07 μm and is different in its solubility depending upon the value of pH is formed on the resist film  602  by, for example, the spin coating: 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 Polymer: polyvinyl sulfonamide 
                  1 g 
               
               
                   
                 Solvent: isopropyl alcohol 
                 20 g 
               
               
                   
                   
               
            
           
         
       
     
     Next, as shown in  FIG. 12C , with an immersion liquid  604  of water provided between the barrier film  603  and a projection lens  606  by, for example, the puddle method, pattern exposure is carried out by irradiating the resist film  602  through the barrier film  603  with exposing light  605  of ArF excimer laser with NA of 0.68 having passed through a mask (not shown). 
     After the pattern exposure, as shown in  FIG. 12D , the resist film  602  is baked with a hot plate at a temperature of 105° C. for 60 seconds (post exposure bake). 
     Next, as shown in  FIG. 13A , the barrier film  603  is removed with, for example, a 0.01 wt % tetramethylammonium hydroxide aqueous solution (diluted alkaline developer). Thereafter, the resultant resist film  602  is developed with a 2.38 wt % tetramethylammonium hydroxide aqueous solution (alkaline developer). In this manner, a resist pattern  602   a  made of an unexposed portion of the resist film  602  and having a line width of 0.09 μm is formed in a good shape as shown in  FIG. 13B . 
     In this manner, according to Embodiment 6, before carrying out the pattern exposure shown in  FIG. 12C , the barrier film  603  including the polymer having a sulfonamide structure (i.e., polyvinyl sulfonamide) is formed on the resist film  602 . Therefore, the resist film  602  is never in direct contact with the immersion liquid  604 . Accordingly, a component of the resist film  602  such as the acid generator or the quencher can be prevented from eluting into the immersion liquid  604  or the immersion liquid  604  can be prevented from permeating into the resist film  602  on the contrary, and hence, the resist film  602  keeps the expected performance of the chemically amplified resist through the exposure and the post exposure bake performed thereafter. As a result, the resist pattern  602   a  made of the resist film  602  is not degraded in its shape. 
     Embodiment 7 
     A pattern formation method using a barrier film material according to Embodiment 7 of the invention will now be described with reference to  FIGS. 14A through 14D  and  15 A through  15 C. 
     First, a positive chemically amplified resist material having the following composition is prepared: 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                 Base polymer: poly((norbornene-5-methylene-t-butyl- 
                 2 
                 g 
               
               
                 carboxylate) (50 mol %) - (maleic anhydride) (50 mol %)) 
               
               
                 Acid generator: triphenylsulfonium triflate 
                 0.06 
                 g 
               
               
                 Quencher: triethanolamine 
                 0.002 
                 g 
               
               
                 Solvent: propylene glycol monomethyl ether acetate 
                 20 
                 g 
               
               
                   
               
            
           
         
       
     
     Next, as shown in  FIG. 14A , the aforementioned chemically amplified resist material is applied on a substrate  701  so as to form a resist film  702  with a thickness of 0.35 μm. 
     Then, as shown in  FIG. 14B , a barrier film  703  that is made of a barrier film material having the following composition, has a thickness of 0.06 μm and is different in its solubility depending upon the value of pH is formed on the resist film  702  by, for example, the spin coating: 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 Polymer: polyvinyl sulfone-N-ethylamide 
                  1 g 
               
               
                   
                 Solvent: n-butyl alcohol 
                 20 g 
               
               
                   
                   
               
            
           
         
       
     
     Next, as shown in  FIG. 14C , the barrier film  703  is annealed with a hot plate at a temperature of 120° C. for 90 seconds, so as to improve the denseness of the barrier film  703 . 
     After the annealing, as shown in  FIG. 14D , with an immersion liquid  704  of water provided between the barrier film  703  and a projection lens  706  by, for example, the puddle method, pattern exposure is carried out by irradiating the resist film  702  through the barrier film  703  with exposing light  705  of ArF excimer laser with NA of 0.68 having passed through a mask (not shown). 
     After the pattern exposure, as shown in  FIG. 15A , the resist film  702  is baked with a hot plate at a temperature of 105° C. for 60 seconds (post exposure bake). 
     Next, as shown in  FIG. 15B , the barrier film  703  is removed with, for example, a 0.005 wt % tetramethylammonium hydroxide aqueous solution (diluted alkaline developer). Thereafter, the resultant resist film  702  is developed with a 2.38 wt % tetramethylammonium hydroxide aqueous solution (alkaline developer). In this manner, a resist pattern  702   a  made of an unexposed portion of the resist film  702  and having a line width of 0.09 μm is formed in a good shape as shown in  FIG. 15C . 
     In this manner, according to Embodiment 7, before carrying out the pattern exposure shown in  FIG. 14D , the barrier film  703  including the polymer having a sulfonamide structure (i.e., polyvinyl sulfone-N-ethylamide) is formed on the resist film  702 . Therefore, the resist film  702  is never in direct contact with the immersion liquid  704 . Accordingly, a component of the resist film  702  such as the acid generator or the quencher can be prevented from eluting into the immersion liquid  704  or the immersion liquid  704  can be prevented from permeating into the resist film  702  on the contrary, and hence, the resist film  702  keeps the expected performance of the chemically amplified resist through the exposure and the post exposure bake performed thereafter. As a result, the resist pattern  702   a  made of the resist film  702  is not degraded in its shape. 
     In addition, in Embodiment 7, since the barrier film  703  is annealed for improving the denseness as shown in  FIG. 14C  before the pattern exposure, the insolubility of the barrier film  703  in the immersion liquid  704  (water) is increased. Therefore, the function of the barrier film  703  as a barrier for preventing the acid generator or the like from eluting from the resist film  702  into the immersion liquid  704  can be improved. 
     Embodiment 8 
     A pattern formation method using a barrier film material according to Embodiment 8 of the invention will now be described with reference to  FIGS. 16A through 16D  and  17 . 
     First, a positive chemically amplified resist material having the following composition is prepared: 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                 Base polymer: poly((norbornene-5-methylene-t-butyl- 
                 2 
                 g 
               
               
                 carboxylate) (50 mol %) - (maleic anhydride) (50 mol %)) 
               
               
                 Acid generator: triphenylsulfonium triflate 
                 0.06 
                 g 
               
               
                 Quencher: triethanolamine 
                 0.002 
                 g 
               
               
                 Solvent: propylene glycol monomethyl ether acetate 
                 20 
                 g 
               
               
                   
               
            
           
         
       
     
     Next, as shown in  FIG. 16A , the aforementioned chemically amplified resist material is applied on a substrate  801  so as to form a resist film  802  with a thickness of 0.35 μm. 
     Then, as shown in  FIG. 16B , a barrier film  803  that is made of a barrier film material having the following composition, has a thickness of 0.07 μm and is different in its solubility depending upon the value of pH is formed on the resist film  802  by, for example, the spin coating: 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 Polymer: polyvinyl sulfone-N-chloromethylamide 
                  1 g 
               
               
                   
                 Solvent: isopropyl alcohol 
                 20 g 
               
               
                   
                   
               
            
           
         
       
     
     Next, as shown in  FIG. 16C , with an immersion liquid  804  of water provided between the barrier film  803  and a projection lens  806  by, for example, the puddle method, pattern exposure is carried out by irradiating the resist film  802  through the barrier film  803  with exposing light  805  of ArF excimer laser with NA of 0.68 having passed through a mask (not shown). 
     After the pattern exposure, as shown in  FIG. 16D , the resist film  802  is baked with a hot plate at a temperature of 105° C. for 60 seconds (post exposure bake). 
     Next, the barrier film  803  is removed and the resultant resist film  802  is developed with a 2.38 wt % tetramethylammonium hydroxide aqueous solution (alkaline developer). In this manner, a resist pattern  802   a  made of an unexposed portion of the resist film  802  and having a line width of 0.09 μm is formed in a good shape as shown in  FIG. 17 . 
     In this manner, according to Embodiment 8, before carrying out the pattern exposure shown in  FIG. 16C , the barrier film  803  including the polymer having a sulfonamide structure (i.e., polyvinyl sulfone-N-chloromethylamide) is formed on the resist film  802 . Therefore, the resist film  802  is never in direct contact with the immersion liquid  804 . Accordingly, a component of the resist film  802  such as the acid generator or the quencher can be prevented from eluting into the immersion liquid  804  or the immersion liquid  804  can be prevented from permeating into the resist film  802  on the contrary, and hence, the resist film  802  keeps the expected performance of the chemically amplified resist through the exposure and the post exposure bake performed thereafter. As a result, the resist pattern  802   a  made of the resist film  802  is not degraded in its shape. 
     Furthermore, in the same manner as in Embodiment 3, since the barrier film  803  is removed during the development, namely, with the alkaline developer, the dissolution characteristic of the resist film  802  can be controlled. 
     Embodiment 9 
     A pattern formation method using a barrier film material according to Embodiment 9 of the invention will now be described with reference to  FIGS. 18A through 18D ,  19 A and  19 B. 
     First, a positive chemically amplified resist material having the following composition is prepared: 
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                 Base polymer: poly((norbornene-5-methylene-t-butyl- 
                 2 
                 g 
               
               
                 carboxylate) (50 mol %) - (maleic anhydride) (50 mol %)) 
               
               
                 Acid generator: triphenylsulfonium triflate 
                 0.06 
                 g 
               
               
                 Quencher: triethanolamine 
                 0.002 
                 g 
               
               
                 Solvent: propylene glycol monomethyl ether acetate 
                 20 
                 g 
               
               
                   
               
            
           
         
       
     
     Next, as shown in  FIG. 18A , the aforementioned chemically amplified resist material is applied on a substrate  901  so as to form a resist film  902  with a thickness of 0.35 μm. 
     Then, as shown in  FIG. 18B , a barrier film  903  that is made of a barrier film material having the following composition, has a thickness of 0.08 μm and is different in its solubility depending upon the value of pH is formed on the resist film  902  by, for example, the spin coating: 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 Polymer: polyvinyl sulfone-N-hydroxyethylamide 
                  1 g 
               
               
                   
                 Solvent: n-amyl alcohol 
                 20 g 
               
               
                   
                   
               
            
           
         
       
     
     Next, as shown in  FIG. 18C , the barrier film  903  is annealed with a hot plate at a temperature of 115° C. for 90 seconds, so as to improve the denseness of the barrier film  903 . 
     After the annealing, as shown in  FIG. 18D , with an immersion liquid  904  of water provided between the barrier film  903  and a projection lens  906  by, for example, the puddle method, pattern exposure is carried out by irradiating the resist film  902  through the barrier film  903  with exposing light  905  of ArF excimer laser with NA of 0.68 having passed through a mask (not shown). 
     After the pattern exposure, as shown in  FIG. 19A , the resist film  902  is baked with a hot plate at a temperature of 105° C. for 60 seconds (post exposure bake). 
     Next, the barrier film  903  is removed and the resultant resist film  902  is developed with a 2.38 wt % tetramethylammonium hydroxide aqueous solution (alkaline developer). In this manner, a resist pattern  902   a  made of an unexposed portion of the resist film  902  and having a line width of 0.09 μm is formed in a good shape as shown in  FIG. 19B . 
     In this manner, according to Embodiment 9, before carrying out the pattern exposure shown in  FIG. 18D , the barrier film  903  including the polymer having a sulfonamide structure (i.e., polyvinyl sulfone-N-hydroxyethylamide) is formed on the resist film  902 . Therefore, the resist film  902  is never in direct contact with the immersion liquid  904 . Accordingly, a component of the resist film  902  such as the acid generator or the quencher can be prevented from eluting into the immersion liquid  904  or the immersion liquid  904  can be prevented from permeating into the resist film  902  on the contrary, and hence, the resist film  902  keeps the expected performance of the chemically amplified resist through the exposure and the post exposure bake performed thereafter. As a result, the resist pattern  902   a  made of the resist film  902  is not degraded in its shape. 
     In addition, in Embodiment 9, since the barrier film  903  is annealed for improving the denseness as shown in  FIG. 18C  before the pattern exposure, the insolubility of the barrier film  903  in the immersion liquid  904  (water) is increased. Therefore, the function of the barrier film  903  as a barrier for preventing the acid generator or the like from eluting from the resist film  902  into the immersion liquid  904  can be improved. 
     Furthermore, since the barrier film  903  is removed during the development, namely, with the alkaline developer, in the same manner as in Embodiment 3, the dissolution characteristic of the resist film  902  can be controlled. 
     Although the exposing light is ArF excimer laser in Embodiments 1 through 4 and 6 through 9 and is F 2  laser in Embodiment 5, the exposing light is not limited to them but may be KrF excimer laser, ArKr laser or Ar 2  laser instead. 
     Furthermore, in each of Embodiments 1 through 9, the refractive index of the immersion liquid may be increased by adding, for example, cesium sulfate (Cs 2 SO 4 ) or phosphoric acid (H 3 PO 4 ) to the immersion liquid. In this case, the concentration of the cesium sulfate or the phosphoric acid is approximately 1 wt % through 10 wt %, which does not limit the invention. 
     Also, the thickness of the barrier film is not limited to the thickness employed in each embodiment, which is specifically 0.03 μm through 0.08 μm. The lower limit of the thickness is a thickness sufficiently larger for preventing a component of the resist film from eluting into the immersion liquid or preventing the immersion liquid from permeating into the resist film, and the upper limit of the thickness is a thickness sufficiently smaller for not preventing transmittance of the exposing light but to be easily removed. For example, the thickness is preferably 0.01 μm through 0.15 μm and more preferably approximately 0.02 μm through 0.10 μm, which does not limit the invention. 
     Furthermore, the puddle method is employed for providing the immersion liquid onto the barrier film in each embodiment, which does not limit the invention, and for example, a dip method in which the whole substrate is dipped in the immersion liquid may be employed instead. 
     Moreover, although a positive chemically amplified resist is used for forming the resist film in each embodiment, the present invention is applicable also to a negative chemically amplified resist. 
     As described so far, according to the barrier film material and the pattern formation method using the same of this invention, the influence of an immersion liquid on a resist film can be prevented, so that a resist pattern can be formed in a good shape. Accordingly, the present invention is useful as a method for forming a fine pattern to be employed in fabrication process or the like for semiconductor devices.