Abstract:
A method for forming a metallic plug capable of preventing the occurrence of defects due to a short between conductive layers and the decrease of reliability in a conductive layer caused by a change of plug resistance by polishing and eliminating a filling film and an adhesive layer using a slurry for polishing a metal after eliminating a part of the filling film by dry etching beforehand. A metal plug can be obtained by the following steps: forming an end connection opened in an interlayer dielectric so as to expose the surface of a conductive layer under the interlayer dielectric; forming an adhesive layer on the exposed conductive layer and on the interlayer dielectric; forming a filling film on the adhesive layer, which fills the end connection completely; eliminating 60% or more of the film thickness of the filling film formed by dry etching; and polishing and eliminating the filling film and the adhesive layer using a slurry for polishing a metal.

Description:
FIELD OF THE INVENTION 
     This invention relates to a method for forming a metallic plug, for example, in a manufacturing process in a silicon semiconductor device. 
     BACKGROUND OF THE INVENTION 
     In order to realize high performance in a silicon semiconductor device, it is necessary to make a device minute and multilayer in structure. However, it has become more difficult to improve reliability in metal wiring, as the device has become smaller. In order to improve reliability in metal wiring, it is particularly necessary to make an extremely large recessed volume of metal small enough in the case of forming a metallic plug that is used for improving reliability at an end connection portion for connecting wires of an upper layer and of a lower layer. Recently, a polishing technique has been introduced into a silicon semiconductor process as a means for reducing a recessed volume. 
     An example of a conventional method for forming a metallic plug using the polishing technology is explained referring to FIGS. 8A-8D as follows. First, an aluminum alloy film is formed on an interlayer dielectric  1 , which insulates an upper wire and a lower wire, by a sputter deposition method or the like. After forming a predetermined resist pattern on the aluminum alloy film by a photolithographic process, the extra aluminum alloy film is eliminated by dry etching and the resist is then also eliminated, thus obtaining a conductive layer  3  as shown in FIG.  8 A. In this case, an example of metal wiring using an aluminum alloy film as the conductive layer  3  is explained, but the conductive layer  3  may be a conductive layer or diffusion layer such as a polycrystalline silicon or the like. 
     Next, a dielectric that is a silicone oxide film is formed by a CVD method and the dielectric is planarized through a planarization process, thus forming an interlayer dielectric  2 . After forming a predetermined resist pattern on the interlayer dielectric  2  by a photolithographic process, an extra dielectric is eliminated by dry etching and the resist is then also eliminated, thus obtaining an end connection  4 . The end connection  4  is used for connecting the conductive layer  3  and another conductive layer formed thereon, and is open so that the surface of the conductive layer  3  is exposed. 
     As a next step, an adhesive layer  5  having a layered structure of a titanium nitride film and a titanium film is formed by a sputter deposition method or the like as shown in FIG. 8B. A tungsten film  6  as a filling film is then formed using a CVD method so as to fill in the end connection  4  completely as shown in FIG.  8 C. The film thickness of the tungsten film  6  is about 0.3 μm-1.0 μm except for the end connection  4  portions. 
     Finally, a metallic plug  7  is obtained by polishing the tungsten film  6  and the adhesive layer  5  using a polishing device until a part of the interlayer dielectric  2  where the end connection  4  is not formed is completely exposed as shown in FIG.  8 D. In a slurry used in the polish, alumina is used as an abrasive grain, and iron nitrate, a hydrogen peroxide solution, potassium iodate or the like is used for adjusting pH. 
     There is no big difference of elevation between the surface of the interlayer dielectric  2  exposed and that of the metallic plug  7 , since tungsten is eliminated by polishing. As a result, the recessed volume at the end connection  4  portions after eliminating the tungsten film  6  can be 0.1 μm or less, thus obtaining a highly reliable conductive layer. 
     However, in the conventional method mentioned above for forming a metallic plug, when the variation in a polishing rate within a substrate in the case of polishing the tungsten film  6  is not small enough with respect to the variation within a substrate in the case of forming a tungsten film, the polishing time until the interlayer dielectric  2  is exposed is different at different places within the substrate. When the polishing time is different, a portion  8  of the adhesive layer  5  that can not be eliminated is created within the substrate as shown in FIG.  8 D. As mentioned above, in the case where the adhesive layer can not be eliminated, reliability in a semiconductor device decreases, since a short occurs between conductive layers in the same layer. 
     Furthermore, even in the case where polishing is conducted only for eliminating the whole tungsten film  6  and adhesive layer  5  within the substrate, a difference of elevation (erosion)  9  depending on a pattern density of the end connection  4  occurs on the surface of the interlayer dielectric  2 , since an area having a rapid polishing rate is overpolished. As mentioned above, pattern formation in a photolithography process becomes difficult, when difference of elevation occurs on an interlayer dielectric. Moreover, height of a metallic plug is different according to the difference of elevation of an interlayer dielectric, which causes great variations in resistance at an end connection. As a result, reliability decreases. 
     SUMMARY OF THE INVENTION 
     The problem mentioned above can be solved by a method for forming a metallic plug of the present invention. It is an object of the present invention to prevent pattern defects by erosion or a short between conductive layers caused by variation in a polishing rate within a substrate and decrease of reliability in a conductive layer by eliminating a filling film by dry etching beforehand before polishing the filling film such as a tungsten film or the like. 
     In order to achieve the object mentioned above, a first method for forming a metallic plug of the present invention comprises the following steps: forming an end connection opened in an interlayer dielectric so as to expose the surface of a conductive layer under the interlayer dielectric; forming an adhesive layer on the conductive layer exposed and on the interlayer dielectric; and forming a filling film on the adhesive layer, which fills the end connection completely. The first method for forming a metallic plug of the present invention is characterized by polishing and eliminating the filling film and the adhesive layer using a slurry for polishing a metal after eliminating the filling film by dry etching beforehand. 
     According to the first method for forming a metallic plug, even in the case of having great variations in a polishing rate within a substrate in the case of polishing the filling film, the variation in the remaining film within the substrate in the case of eliminating the filling film and the adhesive layer completely can be minimized and the volume to be overpolished can be restrained to a low level due to a small volume of the filing film to be polished. As a result, the occurrence of defects due to a short between conductive layers caused by creating a portion where an adhesive layer can not be eliminated can be prevented. In addition, the decrease of reliability in a conductive layer caused by a change of plug resistance due to erosion can be prevented. 
     In the first method for forming a metallic plug, it is preferable that the adhesive layer has a layered structure of a titanium nitride film and a titanium film. In the case where the adhesive layer has a layered structure as mentioned above, a filling film can adhere to a conductive layer tightly enough. 
     In addition, it is preferable that the filling film is a tungsten film. In the case of using the tungsten film, the tungsten film can be eliminated by polishing. 
     Furthermore, it is also preferable that the film thickness of the filling film before being dry etched is in the range of 0.3-1.0 μm at a portion not having an end connection. In the case where the film thickness is in the range mentioned above, the end connection can be completely filled. 
     It is further preferable that a volume of the filling film to be eliminated beforehand is 60% or more of the film thickness of the filling film formed. According to such a method for forming a metallic plug, even in the case of having great variations in a polishing rate within a substrate in the case of polishing a filling film, the variation in the remaining film within the substrate in the case of eliminating the filling film and the adhesive layer completely can be minimized and the volume to be overpolished can be restrained to a low level, since the volume of the filling film to be polished can be reduced definitely and sufficiently. 
     Next, a second method for forming a metallic plug of the present invention comprises the following steps: forming an end connection opened in an interlayer dielectric so as to expose the surface of a conductive layer under the interlayer dielectric; forming an adhesive layer on the conductive layer exposed and on the interlayer dielectric; and forming a filling film on the adhesive layer, which fills the end connection completely. The second method for forming a metallic plug of the present invention is characterized by eliminating the filling film by dry etching beforehand until a part of the adhesive layer where the end connection is not formed is exposed and then polishing and eliminating the adhesive layer exposed using a slurry. 
     According to the second method for forming a metallic plug, even in the case of having great variations in a polishing rate within a substrate in the case of polishing a filling film, the volume to be polished and the volume to be overpolished caused by eliminating the adhesive layer completely can be restrained to a low level, since only the adhesive layer needs to be polished. As a result, the occurrence of defects due to a short between conductive layers caused by creating a portion where an adhesive layer can not be eliminated can be prevented. In addition, the decrease of reliability in a conductive layer caused by a change of plug resistance due to erosion can be prevented. 
     In the second method for forming a metallic plug, it is preferable that the adhesive layer has a layered structure of a titanium nitride film and a titanium film. In the case where the adhesive layer has a layered structure as mentioned above, a filling film can adhere to a conductive layer tightly enough. 
     In addition, it is preferable that the filling film is a tungsten film. In the case where the tungsten film is used, the tungsten film can be eliminated by polishing. 
     Furthermore, it is also preferable that the film thickness of the filling film before being dry etched is in the range of 0.3-1.0 μm at a portion not having an end connection. In the case where the film thickness is in the range mentioned above, the end connection can be completely filled. 
     It is preferable that the polishing rates of the slurry for the adhesive layer and the interlayer dielectric are almost same. In the case of using such a slurry, erosion by overpolish can be reduced. 
     It is further preferable that the polishing rate of the slurry for the filling film is lower than that for the adhesive layer and the interlayer dielectric. In the case of using such a slurry mentioned above, a decrease of reliability in a conductive layer can be prevented, since the surface of a metallic plug does not become lower than that of an interlayer dielectric. 
     Moreover, it is preferable that the slurry is a slurry for polishing an oxide film comprising at least one particle selected from a silicon oxide particle and a ceric oxide particle 
     In the case of using such a slurry mentioned above, for example, if an adhesive layer has a layered structure of a titanium nitride film and a titanium film and a silicon oxide film is used as an interlayer dielectric, erosion by overpolishing can be reduced, since there is no big difference between the polishing rate of an adhesive layer and that of a layer insulation film. Furthermore, in the case of using a tungsten film as a filling film, a decrease of reliability in a conductive layer can be prevented, since the surface of a metallic plug does not become lower than that of an interlayer dielectric due to low polishing rate of the tungsten film. 
     It is also preferable that polishing rates of the slurry for the adhesive layer, the interlayer dielectric and the filling film are almost same. In the case of using such a slurry, erosion by overpolishing can be reduced and the surface of a metallic plug and that of the interlayer dielectric can form an even surface, thus preventing decrease of reliability in a conductive layer. 
     It is further preferable that the slurry is a slurry comprising mixed particles including two or more types of particles. In the case of using such a slurry mentioned above, the polishing rates of the adhesive layer, the interlayer dielectric and the filling film can be almost same. As a result, erosion by overpolishing can be reduced and the surface of a metallic plug and that of the interlayer dielectric can form an even surface, thus preventing the decrease of reliability in a conductive layer. 
     It is preferable that the slurry is a slurry comprising mixed particles of a silicon oxide particle and an alumina particle. 
     Furthermore, it is also preferable that the slurry is a slurry comprising mixed particles of a ceric oxide particle and an alumina particle. 
     In the case of using such a slurry mentioned above, for example, if an adhesive layer has a layered structure of a titanium nitride film and a titanium film and a silicon oxide film is used as an interlayer dielectric, erosion by overpolishing can be reduced, since there is no big difference between the polishing rate of an adhesive layer and that of a layer insulation film. Furthermore, in the case of using a tungsten film as a filling film, the polishing rate of the tungsten film is almost same as that of the adhesive layer and the interlayer dielectric. As a result, the surface of a metallic plug and that of the interlayer dielectric can form an even surface, thus preventing the decrease of reliability in a conductive layer. 
     Next, a third method for forming a metallic plug of the present invention comprises the following steps: forming an end connection opened in an interlayer dielectric so as to expose the surface of a conductive layer under the interlayer dielectric; forming an adhesive layer on the conductive layer exposed and on the interlayer dielectric; and forming a filling film on the adhesive layer, which fills the end connection completely. The third method for forming a metallic plug of the present invention is characterized by eliminating the filling film and the adhesive layer by dry etching beforehand until the part of the interlayer dielectric where the end connection is not formed is exposed and then polishing and eliminating the residue of the adhesive layer using a slurry for polishing a metal. 
     According to the third method for forming a metallic plug, even in the case of having great variations in a polishing rate within a substrate in the case of polishing, the volume to be polished and also the volume to be overpolished can be restrained to a low level, since only the residue of the adhesive layer needs to be eliminated. As a result, the occurrence of defects due to a short between conductive layers caused by creating a portion where an adhesive layer can not be eliminated can be prevented. In addition, decrease of reliability in a conductive layer caused by change of a plug resistance due to erosion can be prevented. 
     In the third method for forming a metallic plug, it is preferable that the adhesive layer has a layered structure of a titanium nitride film and a titanium film. In the case where the adhesive layer has a layered structure as mentioned above, a filling film can adhere to a conductive layer tightly enough. 
     In addition, it is preferable that the filling film is a tungsten film. In the case where the tungsten film is used, the tungsten film can be eliminated by polishing. 
     Furthermore, it is also preferable that the film thickness of the filling film before being dry etched is in the range of 0.3-1.0 μm at a portion not having an end connection. In the case where the film thickness is in the range mentioned above, the end connection can be completely filled. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1A-1E show cross-sectional views of a semiconductor device being processed according to an Embodiment 1 of a method for forming a metallic plug of the present invention. 
     FIGS. 2A-2E show cross-sectional views of a semiconductor device being processed according to an Embodiment 2 of a method for forming a metallic plug of the present invention. 
     FIGS. 3A-3E show cross-sectional views of a semiconductor device being processed according to an Embodiment 3 of a method for forming a metallic plug of the present invention. 
     FIGS. 4A-4E show cross-sectional views of a semiconductor device being processed according to an Embodiment 4 of a method for forming a metallic plug of the present invention. 
     FIG. 5 is a graph illustrating an example of the relationship between the type of film polished and the polishing rate according to Embodiment 4 of the present invention. 
     FIGS. 6A-6E show cross-sectional views of a semiconductor device being processed according to an Embodiment 5 of a method for forming a metallic plug of the present invention. 
     FIG. 7 is a graph illustrating an example of the relationship between the type of film polished and the polishing rate according to Embodiment 5 of the present invention. 
     FIGS. 8A-8D show cross-sectional views of a semiconductor device being processed according to a conventional method for forming a metallic plug. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     (Embodiment 1) 
     Embodiment 1 of a method for forming a metallic plug of the present invention will be explained referring to the figures as follows. FIGS. 1A-1E includes cross-sectional views of a semiconductor device in a manufacturing process of a metallic plug according to Embodiment 1 of the present invention. In FIGS. 1A-1E, each of A, B and C indicates a process for forming a tungsten film  6 , which is identified with the same number as in FIGS. 8A-8D, and the explanation is omitted, since these processes are identical to those of the conventional example explained using FIGS. 8A-8D. 
     A process after forming a tungsten film  6  will be explained as follows. After forming a tungsten film  6 , the tungsten film  6  is eliminated by dry etching as shown in FIG. 1D. A numeral  10  is the tungsten film after being eliminated by dry etching. Dry etching having a uniform etching rate within a substrate and a high etching rate is generally employed. The volume eliminated by etching is 60% or more of the film thickness of the tungsten film formed. In this case, the film thickness to be a reference of the volume to be eliminated is the film thickness between the surface of a part of an adhesive layer  5  where an end connection  4  is not formed and the surface of the tungsten film  6 . That is to say, the film thickness of the tungsten film  6  at the end connection  4  portion is not included. In this Embodiment, the film thickness of the tungsten film is in the range of 0.3-1.0 μm (same as in Embodiments 2-5 below). 
     Finally, a metallic plug  11  is obtained by polishing the tungsten film  10  and the adhesive layer  5  using a slurry for polishing a metal until a part of the interlayer dielectric  2  where the end connection  4  is not formed is completely exposed as shown in FIG.  1 E. 
     When a metallic plug is formed according to such a method mentioned above, even in the case of having great variations in a polishing rate within a substrate in the case of polishing a tungsten film, the variation in the remaining film within the substrate in the case of eliminating the tungsten film and the adhesive layer completely can be minimized and the volume to be overpolished can be restrained to a low level due to the small volume of the tungsten film to be polished. As a result, the occurrence of defects due to a short between conductive layers caused by creating a portion where an adhesive layer can not be eliminated can be prevented. In addition, the decrease of reliability in a conductive layer caused by the change of plug resistance due to erosion can be prevented. 
     (Embodiment 2) 
     Embodiment 2 of a method for forming a metallic plug of the present invention will be explained referring to the figures as follows. FIGS. 2A-2E includes cross-sectional views of a semiconductor device in a manufacturing process of a metallic plug according to Embodiment 2 of the present invention. In FIGS. 2A,  2 B, and  2 C indicates a process for forming a tungsten film  6 , which is identified with the same number as in FIGS. 8A-8D, and the explanation is omitted, since these processes are identical to those of the conventional example explained using FIGS. 8A-8D. 
     A process after forming a tungsten film  6  will be explained as follows. After forming a tungsten film  6 , the tungsten film  6  is eliminated by dry etching until a part of the adhesive layer  5  where the end connection  4  is not formed is exposed as shown in FIG. 2D, thus obtaining a tungsten film  12 . Dry etching having a uniform etching rate within a substrate and a high etching rate is generally employed. 
     Finally, a metallic plug  13  is obtained by polishing the adhesive layer  5  using a slurry for polishing a metal until a part of the interlayer dielectric  2  where the end connection  4  is not formed is completely exposed as shown in FIG.  2 E. 
     When a metallic plug is formed according to such a method mentioned above, even in the case of having great variations in a polishing rate within a substrate in the case of polishing a tungsten film, the volume to be polished and the volume to be overpolished caused by eliminating an adhesive layer completely can be restrained to a low level, since only the adhesive layer needs to be polished. As a result, the occurrence of defects due to a short between conductive layers caused by creating a portion where an adhesive layer can not be eliminated can be prevented. In addition, the decrease of reliability in a conductive layer caused by a change of plug resistance due to erosion can be prevented. 
     (Embodiment 3) 
     Embodiment 3 of a method for forming a metallic plug of the present invention will be explained referring to the figures as follows. FIGS. 3A-3E includes cross-sectional views of a semiconductor device in a manufacturing process of a metallic plug according to Embodiment 3 of the present invention. In FIGS. 3A,  3 B, and  3 C indicates a process for forming a tungsten film  6 , which is identified with the same number as in FIGS. 8A-8D, and the explanation is omitted, since these processes are identical to those of the conventional example explained using FIGS. 8A-8D. 
     A process after forming a tungsten film  6  will be explained as follows. After forming a tungsten film  6 , the tungsten film  6  and an adhesive layer  5  are eliminated by dry etching as shown in FIG. 3D. A numeral  14  is the tungsten film after being eliminated by dry etching. Dry etching having a uniform etching rate within a substrate and a high etching rate is generally employed. A volume to be eliminated by etching is defined as etching until a part of the interlayer dielectric  2  where the end connection  4  is not formed is exposed. A numeral  15  indicates a residue of the adhesive layer etched until the interlayer dielectric  2  is exposed. That is to say, the adhesive layer  5  remains as the residue  15  in a portion where the interlayer dielectric  2  is not completely exposed. 
     Finally, a metallic plug  16  is obtained by polishing the residue  15  of the adhesive layer  5  using a slurry for polishing a metal until the residue  15  of the adhesive layer  5  is completely eliminated as shown in FIG.  3 E. 
     When a metallic plug is formed according to such a method mentioned above, even in the case of having great variations in a polishing rate within a substrate in the case of polishing, the volume to be polished and the volume to be overpolished can be restrained to a low level, since only the residue of an adhesive layer needs to be eliminated. As a result, the occurrence of defects due to a short between conductive layers caused by creating a portion where an adhesive layer can not be eliminated can be prevented. In addition, the decrease of reliability in a conductive layer caused by a change of plug resistance due to erosion can be prevented. 
     (Embodiment 4) 
     Embodiment 4 of a method for forming a metallic plug of the present invention will be explained referring to the figures as follows. FIGS. 4A-4E includes cross-sectional views of a semiconductor device in a manufacturing process of a metallic plug according to Embodiment 4 of the present invention. In FIGS. 4A,  4 B, and  4 C indicates a process for forming a tungsten film  6 , which is identified with the same number as in FIGS. 8A-8D , and the explanation is omitted, since these processes are identical to those of the conventional example explained using FIGS. 8A-8D. 
     A process after forming a tungsten film  6  will be explained as follows. After forming a tungsten film  6 , the tungsten film  6  is eliminated by dry etching until a part of an adhesive layer  5  where the end connection  4  is not formed is exposed as shown in FIG. 4D, thus obtaining a tungsten film  12 . Dry etching having a uniform etching rate within a substrate and a high etching rate is generally employed. 
     Finally, a metallic plug  17  is obtained by polishing the adhesive layer  5  using a slurry for polishing an oxide film comprising a silicon oxide particle or a ceric oxide particle until a part of the interlayer dielectric  2  where the end connection  4  is not formed is completely exposed as shown in FIG.  4 E. 
     When a metallic plug is formed according to such a method mentioned above, erosion by overpolishing can be reduced, since there is no big difference between the polishing rate of the adhesive layer  5  having a layered structure of a titanium nitride film and a titanium film and that of the interlayer dielectric  2  that is a silicon oxide film as in an example shown in FIG.  5 . As a result, the occurrence of defects due to a short between conductive layers caused by creating a portion where an adhesive layer can not be eliminated can be prevented. In addition, the decrease of reliability in a conductive layer caused by a change of plug resistance due to erosion can be prevented. Furthermore, the surface of a metallic plug does not become lower than the surface of an interlayer dielectric, since the polishing rate of the tungsten film is small, thus improving reliability in a conductive layer. 
     (Embodiment 5) 
     Embodiment 5 of a method for forming a metallic plug of the present invention will be explained referring to the figures as follows. FIGS. 6A-6E includes cross-sectional views of a semiconductor device in a manufacturing process of a metallic plug according to Embodiment 5 of the present invention. In FIGS. 6A,  6 B, and  6 C indicates a process for forming a tungsten film  6 , which is identified with the same number as in FIG. 8, and the explanation is omitted, since these processes are identical to those of the conventional example explained using FIGS. 8A-8D. 
     A process after forming a tungsten film  6  will be explained as follows. After forming a tungsten film  6 , the tungsten film  6  is eliminated by dry etching until a part of the adhesive layer  5  where the end connection  4  is not formed is exposed as shown in FIG. 6D, thus obtaining a tungsten film  12 . Dry etching having a uniform etching rate within a substrate and a high etching rate is generally employed. 
     Finally, a metallic plug  18  is obtained by polishing the adhesive layer  5  using a slurry comprising mixed particles until a part of the interlayer dielectric  2  where the end connection  4  is not formed is completely exposed as shown in FIG.  6 E. The mixed particles included in the slurry are preferably mixed particles including two or more particles such as mixed particles of a silicon oxide particle and an alumina particle, of a ceric oxide particle and an alumina particle or the like. 
     When a metallic plug is formed according to such a method mentioned above, erosion by overpolishing can be reduced, since there is no big difference between the polishing rate of the adhesive layer  5  having a layered structure of a titanium nitride film and a titanium film and that of the interlayer dielectric  2  that is a silicon oxide film as in an example shown in FIG.  7 . As a result, the occurrence of defects due to a short between conductive layers caused by creating a portion where an adhesive layer can not be eliminated can be prevented. In addition, the decrease of reliability in a conductive layer caused by a change of plug resistance due to erosion can be prevented. Furthermore, the surface of a metallic plug  18  and that of the interlayer dielectric  2  forms an even surface as shown in FIG. 6E, since the polishing rate of the tungsten film  12  is also almost same as that of the adhesive layer  5  and that of the interlayer dielectric  2 , thus preventing the decrease of reliability in a conductive layer. 
     In Embodiments 1-5 mentioned above, the explanation was made using a tungsten film as a filling film, but the same effect can be also obtained in the case of using another filling metal. 
     Moreover, the explanation was made using metal wiring composed of aluminum alloy as a conductive layer  3 , but the same effect can be also obtained in the case of using a conductive layer or diffusion layer such as polycrystalline silicon or the like. 
     As mentioned above, according to a method for forming a metallic plug of the present invention, after eliminating a filling film by dry etching beforehand, the filling film and an adhesive layer are eliminated by polishing using a slurry for polishing a metal, thus preventing the occurrence of defects due to a short between conductive layers and the decrease of reliability in a conductive layer by a change of plug resistance. 
     Furthermore, after eliminating a filling film by dry etching beforehand until a part of an adhesive layer where an end connection is not formed is exposed, the adhesive layer exposed is eliminated by polishing using a slurry, thus preventing the occurrence of defects due to a short between conductive layers and the decrease of reliability in a conductive layer by a change of plug resistance. 
     Moreover, after eliminating a filling film and an adhesive layer by dry etching beforehand until a part of an interlayer dielectric where the end connection is not formed is exposed, the residue of the adhesive layer is eliminated by polishing using a slurry for polishing a metal, thus preventing the occurrence of defects due to a short between conductive layers and the decrease of reliability in a conductive layer by a change of plug resistance. 
     The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The embodiments disclosed in this application are to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.