Abstract:
Disclosed is a semiconductor device comprising a semiconductor substrate, a capacitor provided above the semiconductor substrate and including a bottom electrode, a top electrode, and a dielectric film provided between the top electrode and the bottom electrode, an insulating region surrounding the capacitor and having a first hole which extends in a vertical direction and reaches the top electrode and a second hole which extends in the vertical direction and is spaced away from the capacitor, and a first wiring connected to the top electrode and including a first conductive portion formed in the first hole and a second conductive portion formed in the second hole, the first wiring having a barrier metal film between the insulating region and the first conductive portion and having no barrier metal film between the insulating region and the second conductive portion.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2002-298500, filed Oct. 11, 2002, the entire contents of which are incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a semiconductor device having a capacitor and a method of manufacturing the same.  
           [0004]    2. Description of the Related Art  
           [0005]    Research and development is conducted on nonvolatile memories (FeRAMs) using a ferroelectric film such as a PZT film (Pb(Zr,Ti)O 3  film) for a dielectric film of a capacitor.  
           [0006]    A prior art method of manufacturing a ferroelectric memory will now be described with reference to FIGS. 3A to  3 D.  
           [0007]    Referring first to FIG. 3A, a MIS transistor  12 , an interlayer insulation film  13 , a W plug  14 , a silicon nitride film  15  and a silicon oxide film  16  are formed on a semiconductor substrate  11 . A ferroelectric capacitor including a bottom electrode  21 , a ferroelectric film  22  and a top electrode  23  is formed on the silicon oxide film  16 . The bottom and top electrodes  21  and  23  are formed of a platinum (Pt) film, an iridium (Ir) film, an IrO 2  film or the like. The ferroelectric film  22  is formed of a PZT film or the like. An interlayer insulation film  24  is formed on the entire surface of the resultant structure and patterned to form a connecting hole  31  that reaches the top electrode  23 , a connecting hole  32  that reaches the bottom electrode  21  and a connecting hole  33  that reaches the W plug  14 .  
           [0008]    Referring now to FIG. 3B, a barrier metal film such as TIN and an Al film are deposited in sequence. By performing processing such as CMP, a barrier metal film  34   a  and an Al film  35   a  are formed in the connecting hole  31 , a barrier metal film  34   b  and an Al film  35   b  are formed in the connecting hole  32  and a barrier metal film  34   c  and an Al film  35   c  are formed in the connecting hole  33 . The barrier metal films prevent the Al films from being alloyed with the films (Pt film, Ir film, etc.) used for the bottom and top electrodes  21  and  23 .  
           [0009]    Referring now to FIG. 3C, a silicon oxide film  36  is deposited on the entire surface of the resultant structure and patterned to form trenches  37  and  38 . An Al film  39   a  is formed in the trench  37  and an Al film  39   b  is formed in the trench  38 , as shown in FIG. 3D.  
           [0010]    In the above steps, a wiring including the Al films  35   a,    39   a  and  35   c  is connected to the top electrode  23  of the capacitor, and a wiring including the Al films  35   b  and  39   b  is connected to the bottom electrode  21  of the capacitor.  
           [0011]    In the foregoing prior art manufacturing method, however, the barrier metal and Al films are formed in the connecting hole  33  as well as the connecting holes  31  and  32 . The connecting hole  33  is deeper than the connecting holes  31  and  32  and the diameter of the hole  33  is generally smaller than that of each of the holes  31  and  32 . If, therefore, the semiconductor device is microfabricated, the barrier metal and Al films become difficult to completely bury in the connecting hole  33  and thus a void or the like easily occurs in the Al film. Consequently, the wiring greatly deteriorates in characteristic and reliability.  
           [0012]    Jpn. Pat. Appln. KOKAI Publication No. 2001-102538 proposes a technique of burying metal in a contact hole and a trench at once in a ferroelectric memory. If, however, a barrier metal film is used in the structure proposed in the Publication, the barrier metal film and metal film are difficult to completely bury in a deep contact hole (connecting hole), when a semiconductor device is microfabricated. For this reason, a wiring greatly deteriorates in characteristic and reliability.  
           [0013]    According to the prior art ferroelectric memories described above, the barrier metal film and Al film are formed even in a connecting hole in a region that separates from the capacitor. Thus, the Al film becomes difficult to bury in the connecting hole and the wiring greatly deteriorates in characteristic and reliability.  
         BRIEF SUMMARY OF THE INVENTION  
         [0014]    According to a first aspect of the present invention, there is provided a semiconductor device comprising: a semiconductor substrate; a capacitor provided above the semiconductor substrate and including a bottom electrode, a top electrode, and a dielectric film provided between the top electrode and the bottom electrode; an insulating region surrounding the capacitor and having a first hole which extends in a vertical direction and reaches the top electrode and a second hole which extends in the vertical direction and is spaced away from the capacitor; and a first wiring connected to the top electrode and including a first conductive portion formed in the first hole and a second conductive portion formed in the second hole, the first wiring having a barrier metal film between the insulating region and the first conductive portion and having no barrier metal film between the insulating region and the second conductive portion.  
           [0015]    According to a second aspect of the present invention, there is provided a method of manufacturing a semiconductor device comprising: forming a capacitor above a semiconductor substrate, the capacitor being surrounded with an insulating region and including a bottom electrode, a top electrode and a dielectric film provided between the top electrode and the bottom electrode; and forming a first wiring connected to the top electrode, forming the first wiring including: removing part of the insulating region to form a first hole which extends in a vertical direction and reaches the top electrode; forming a barrier metal film in the first hole; forming a first conductive portion in the first hole in which the barrier metal film is formed; removing part of the insulating region to form a second hole which extends in the vertical direction and is spaced away from the capacitor; and forming a second conductive portion in the second hole without forming a barrier metal film in the second hole. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0016]    [0016]FIGS. 1A to  1 D are sectional views schematically showing a method of manufacturing a semiconductor device according to a first embodiment of the present invention;  
         [0017]    [0017]FIGS. 2A to  2 D are sectional views schematically showing a method of manufacturing a semiconductor device according to a second embodiment of the present invention; and  
         [0018]    [0018]FIGS. 3A to  3 D are sectional views schematically showing a method of manufacturing a prior art semiconductor device. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]    Embodiments of the present invention will now be described with reference to the accompanying drawings.  
       FIRST EMBODIMENT  
       [0020]    [0020]FIGS. 1A to  1 D are sectional views schematically showing a method of manufacturing a semiconductor device (ferroelectric memory) according to a first embodiment of the present invention.  
         [0021]    Referring first to FIG. 1A, a MIS transistor  12  is formed on a semiconductor substrate  11  such as a silicon substrate. An interlayer insulation film  13  such as a silicon oxide film (SiO 2  film) is formed on the entire surface of the resultant structure. A connecting hole is opened in the interlayer insulation film  13  to reach the source or drain of the MIS transistor  12  and filled with a W plug  14 . A silicon nitride film (SiN film)  15  and a silicon oxide film (SiO 2  film)  16  are formed on the entire surface of the resultant structure.  
         [0022]    A ferroelectric capacitor is formed on the silicon oxide film  16  and includes a bottom electrode  21 , a ferroelectric film  22  formed on the bottom electrode  21  and a top electrode  23  formed on the ferroelectric film  22 . The bottom and top electrodes  21  and  23  are formed of a platinum (Pt) film, an iridium (Ir) film, an IrO 2  film or the like. The ferroelectric film  22  is formed of a PZT film (Pb(Zr,Ti)O 3  film) or the like.  
         [0023]    An interlayer insulation film  24  such as a silicon oxide film is formed on a region including the capacitor. As a result, the capacitor is surrounded with an insulating region including the silicon oxide film  16  and interlayer insulation film  24 . The interlayer insulation film  24  is patterned by photolithography and RIE to form a connecting hole  51  that reaches the top electrode  23  and a connecting hole  52  that reaches the bottom electrode  21 .  
         [0024]    Referring now to FIG. 1B, a barrier metal film and a metal film are deposited in sequence on the entire surface of the structure including the connecting holes  51  and  52 . The barrier metal film is formed of a TiN film, a NbN film, a TaN film, a TaAlN film or a stacked structure of these films. The metal film is formed of an Al film. An unnecessary portion is removed from the barrier metal film and metal film by CMP to leave the barrier metal film  53   a  and metal film  54   a  (conductive portion) in the connecting hole  51  and leave the barrier metal film  53   b  and metal film  54   b  (conductive portion) in the connecting hole  52 . In order to bury the metal films  54   a  and  54   b  in their respective connecting holes  51  and  52  by reflow of Al, a liner film is formed in advance on the barrier metal films  53   a  and  53   b.  The liner film differs from the barrier metal films  53   a  and  53   b  and is formed of, e.g., a Ti film or a Nb film.  
         [0025]    Referring now to FIG. 1C, a silicon oxide film  55  is deposited as an insulating film on the entire surface of the resultant structure. The silicon oxide film  55 , interlayer insulation film  24 , silicon oxide film  16  and silicon nitride film  15  are patterned by photolithography and RIE. Thus, a connecting hole  56  that reaches the W plug  14  is formed and so are trenches  57  and  58 .  
         [0026]    Referring now to FIG. 1D, an Al film is formed as a metal film on the entire surface of the resultant structure. An unnecessary portion is removed from the metal film by CMP. Thus, a conductive portion of a metal film  59  is formed in the connecting hole  56 , a conductive portion of a metal film  60   a  is formed in the trench  57  and a conductive portion of a metal film  60   b  is formed in the trench  58 . To form the metal films  59 ,  60   a  and  60   b  by reflow of Al, a liner film is formed in advance. The liner film differs from the barrier metal films  53   a  and  53   b  and is formed of, e.g., a Ti film or a Nb film.  
         [0027]    The top electrode  23  of the capacitor and the W plug  14  connected to the source or drain of the MIS transistor  12  are connected to each other through a wiring including the conductive portion  54   a  extending in the vertical direction, the conductive portion  60   a  extending in the horizontal direction, and the conductive portion  59  extending in the vertical direction. The bottom electrode  21  of the capacitor is connected to a wiring including the conductive portion  54   b  extending in the vertical direction and the conductive portion  60   b  extending in the horizontal direction.  
         [0028]    According to the first embodiment described above, the connecting holes  51  and  52  are formed to reach the bottom and top electrodes  21  and  23 , then the barrier metal film and metal film (Al film) are formed in the connecting holes  51  and  52 , and then the connecting hole  56  is formed to reach the W plug  14 . Accordingly, no barrier metal film is formed in the connecting hole  56 . The barrier metal film prevents the metal film (Al film, etc.) serving as a wiring film from being alloyed with the metal films (Pt film, Ir film, etc.) used for the bottom and top electrodes  21  and  23 . No problems therefore occur even though no barrier metal film is formed in the connecting hole  56 . According to the first embodiment, therefore, the metal film serving as a wiring film and the metal films used for the bottom and top electrodes can be prevented from being alloyed with each other, and the metal film can reliably and easily be buried into the connecting hole that separates from the capacitor. Consequently, even though the semiconductor device is microfabricated, the wiring can be improved in characteristic and reliability.  
       SECOND EMBODIMENT  
       [0029]    [0029]FIGS. 2A to  2 D are sectional views schematically showing a method of manufacturing a semiconductor device (ferroelectric memory) according to a second embodiment of the present invention. The components corresponding to those shown in FIGS. 1A to  1 D are indicated by the same reference numerals and their detailed descriptions are omitted.  
         [0030]    The fundamental step shown in FIG. 2A is the same as that shown in FIG. 1A. More specifically, a ferroelectric capacitor including a bottom electrode  21 , a ferroelectric film  22  and a top electrode  23  is formed and then an interlayer insulation film  24  is formed to cover the ferroelectric capacitor. The interlayer insulation film  24  is patterned by photolithography and RIE to form a connecting hole  71  that reaches the top electrode  23  and a connecting hole  72  that reaches the bottom electrode  21 .  
         [0031]    Referring now to FIG. 2B, a barrier metal film is deposited on the entire surface of the structure including the connecting holes  71  and  72 . The barrier metal film is formed of a TiN film, a NbN film, a TaN film, a TaAlN film or a stacked structure of these films. An unnecessary portion is removed from the barrier metal film by CMP to leave the barrier metal  73   a  along the inner surface of the connecting hole  71  and leave a barrier metal film  73   b  along the inner surface of the connecting hole  72 .  
         [0032]    Referring now to FIG. 2C, the interlayer insulation film  24 , silicon oxide film  16  and silicon nitride film  15  are patterned by photolithography and RIE to form a connecting hole that reaches a W plug  14 . A metal film (Al film) is deposited on the entire surface of the resultant structure. An unnecessary portion is removed from the metal film by CMP to leave metal films  74   a,    74   b  and  74   c  as conductive portions in the connecting holes  71  and  72  and the connecting hole that reaches the W plug  14 , respectively. In order to form the metal films  74   a,    74   b  and  74   c  in the connecting holes by reflow of Al, the same liner film as that in the first embodiment is formed in advance.  
         [0033]    Referring now to FIG. 2D, a silicon oxide film  75  is deposited on the entire surface of the resultant structure as an insulating film. The silicon oxide film  75  is patterned by photolithography and RIE to form a trench that reaches the metal films  74   a  and  74   c  and a trench that reaches the metal film  74   b.  After that, an Al film is formed on the entire surface of the resultant structure as a metal film. An unnecessary portion is removed from the metal film by CMP to form a conductive portion of a metal film  76   a  and a conductive portion of a metal film  76   b  in their respective trenches. In order to form the metal films  76   a  and  76   b  by reflow of aluminum, the same liner film as that in the first embodiment is formed in advance.  
         [0034]    The top electrode  23  of the capacitor and the W plug  14  connected to the source or drain of the MIS transistor  12  are connected to each other through a wiring including the conductive portion  74   a  extending in the vertical direction, the conductive portion  76   a  extending in the horizontal direction and the conductive portion  74   c  extending in the vertical direction. The bottom electrode  21  of the capacitor is connected to a wiring including the conductive portion  74   b  extending in the vertical direction and the conductive portion  76   b  extending in the horizontal direction.  
         [0035]    In the second embodiment described above, too, no barrier metal film is formed in the connecting hole that reaches the W plug  14 . Accordingly, as in the first embodiment, the metal film serving as a wiring film is prevented from being alloyed with the metal films used for the bottom and top electrodes, and the metal film can reliably and easily be buried into the connecting hole that separates from the capacitor. Consequently, even though the semiconductor device is microfabricated, the wiring can be improved in characteristic and reliability.  
         [0036]    In the foregoing second embodiment, the metal films  74   a,    74   b  and  74   c  are formed in the connecting holes in the same step. However, these metal films can be formed as follows: First, the barrier metal films  73   a  and  73   b  are formed in the step shown in FIG. 2B and then the metal films  74   a  and  74   b  are formed. After that, a connecting hole that reaches the W plug  14  is formed and the metal film  74   c  is formed in the connecting hole.  
         [0037]    In the foregoing second embodiment, the metal films  76   a  and  76   b  are buried in the trenches formed in the silicon oxide film  75  in the step shown in FIG. 2D. However, after the step shown in FIG. 2C, a metal film can be formed in the entire surface of the structure and then patterned by RIE or the like to form the metal films  76   a  and  76   b.    
         [0038]    In the foregoing first and second embodiments, a conductive portion connected to the bottom electrode  21  is provided on the upper side of the bottom electrode. However, the conductive portion can be provided on the lower side of the bottom electrode (a so-called COP structure).  
         [0039]    In the foregoing first and second embodiments, a conductive portion (conductive portion  59  in FIGS. 1A to  1 D and conductive portion  74   c  in FIGS. 2A to  2 D) is connected to the source or drain of the MIS transistor  12  through the W plug  14 . However, the conductive portion can be connected to the source or drain without providing the W plug  14 .  
         [0040]    In the foregoing first and second embodiments, the Al film is used as a metal film to be formed in the connecting hole or the trench. However, the Al film can be replaced with a Cu film or a W film.  
         [0041]    Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.