Abstract:
There is provided a method for forming a capacitor of a semiconductor device capable of improving an oxygen diffusion prevention characteristic and preventing leak current from increasing. The invention is characterized that a lower electrode is formed from a double layer comprising a Pt film and Ir film in forming a dielectric layer having a high dielectric characteristic on a lower electrode.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to semiconductor manufacturing, and more particularly, in forming a capacitor having a dielectric layer deposited at high temperature in oxygen containing ambient.  
           [0002]    To increase capacitance of a capacitor included in high density DRM devices, a (Ba, Sr)TiC 3  film having a high dielectric characteristic is used to the dielectric layer of a capacitor.  
           [0003]    [0003]FIG. 1 is a section view showing the process according to the prior art. As illustrated FIG. 1, by selectively etching an insulated layer  11  formed on a semiconductor surface  10 , a contact hole exposuring the semiconductor substrate  10  is formed, after that a polyslicon plug  12  is formed in the contact hole. Then, a titanium(Ti) film  13  and titanium nitride(TiN) l 4  are formed to prevent silicon from diffusing from the polysilicon plug  12  to the lower electrode of a capacitor, and platinum(Pt) film  15  constructing a lower electrode of a capacitor is formed on the TiN film  14 . Ther, patterning the Pt film  15 , TiN film  14 , and Ti film  13  forms a diffusion barrier pattern and a lower electrode pattern, after that a (Ba, Sr)Ti 3  dielectric layer  16  and a Pt upper electrode  17  are formed on the lower electrode.  
           [0004]    Since a (Ea, Sr)TiO 3  film is deposited at hich temperature in oxygen containing ambient, a lower electrode must have a good oxygen diffusion prevention characteristic. However, since the Pt film being used to a lower electrode doesn&#39;t have an oxygen diffusion prevention characteristic, there is a problem that a nitride system film being used to a diffusion barrier of polysilicon, such as TiN, TaN, WN, is oxidized. To solve the problems, an iridium(Ir) film is formed instead of a Pt film, and oxidizing the Ir film at temperature of more than 450° C. forms an iridium oxide(IrO 2 )film having a good oxygen diffusion prevention characteristic as a lower electrode. However, oxidized electrodes, such as IrO 2  film, are tended to increase leak current due to a small difference of work function with a (Be, Sr)TiO 3  film.  
         SUMMARY OF THE INVENTION  
         [0005]    An object of the present invention is to provide a method for forming a capacitor of a semiconductor device capable of improving an oxygen diffusion prevention characzeristic and preventing leak current from increasing.  
           [0006]    In accord with the object cf the present invention, there is provided a method for forming a capacitor of a semiconductor device comprising the steps of: forming a polysilicon plug on a semiconductor substrate; forming a diffusion barrier comprising a titanium(Ti) film and titanium nitride(TiN) on the polysilicon plug; sequentially depositinc an iridium 1 r) film and a platinum(Pt) film on the diffusion barrier; patterning the diffusion barrier, the Ir film, and the Pt film, and forming a lower electrode; forming a dielectric layer on the Pt film at high temperature in oxygen containing ambient; and forming an upper electrode on the dielectric layer.  
           [0007]    The present invention is characterized that the lower electrode of a capacitor having a dielectric layer formed at high temperature in oxygen containing ambient is formed from a double layer comprising an Ir film and Pt film, whereby it can prevent oxygen from diffusing and prevent leak current from increasing in depositing a dielectric layer at hig.h temperature in oxygen containing ambient. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0008]    The object, features and advantages of the present invention are understood within the context of the description of the preferred embodiment as set forth below. The description of the preferred embodiment is understood within the context Pf accompanying drawino. Which form a material part of this disclosure, wherein:  
         [0009]    [0009]FIG. 1 is a section view showing the process according to a prior art;  
         [0010]    [0010]FIG. 2A- 2 D are section views showing the process according to the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0011]    The description of the preferred embodiment as set forth below.  
         [0012]    [0012]FIG. 2A to FIG. 2D are section views showing the capacitor forming processes of an embodiment of the present invention.  
         [0013]    As illustrated to FIG. 2A, by selectively etching an insulated layer  21  on a semiconductor substrate  20 , a contact hole exposuring the semiconductor substrate  20  is formed, and a polysilicon film is formed on the whole structure in range of 500Å-3000Å thick by chemical vapor deposition. Then, the polysilicon film is polished by chemical mechanical polishing to form a polysilicon plug  22  in the contact hole.  
         [0014]    Then, a Ti film  23  and TiN film  24  constructing a diffusion barrier are formed on the whole structure by a sputtering method. It is preferable that the Ti film  23  and TiN film  24  have a thickness of 200Å-300Å and 500Å-1000Å respectively. Then, a rapid thermal process is performed at temperature of 600° C.-700° C. in oxygen containing ambient for 10-30 seconds, so that a TiSi x  film  26  is formed on the boundary of the Ti film  23  and the polysilicon pluo  22  and a TiNO film  25  is formed on the TiN film  24 . The TiNlO film  25  prevents silicon from diffusing from the polysilicon pluc  22  to the lower electrode of a capacitor.  
         [0015]    Then, as illustrated Fic.  2 B, ar Ir film  27  and a first Pt film  28  are sequentially formed on the TiNC film  25 . The Ir film  27  is formed by sputterino in range of 100Å-500Å thick for preventing the TiN film  24  from being oxidized, and the first Pt film  28  is formed by sputtering at temperature of 500° C. -600° C. in range of 500Å-1000Å thick.  
         [0016]    Then, as illustrated FIG. 2C, the first Pt film  28 , Ir film  27 , TiNO film  25 , TiN film  24 , and Ti film  23  are patterned to form a diffusion barrier pattern consisting of the TiNO film  25 , TiN film  24 , and Ti film  23  and a lower electrode pattern consisting of the first Pt film  28  and Ir film  27 .  
         [0017]    Then, as illustrated FIG. 2D, a (Ba, Sr)TiO. film  2 O having a high dielectric characteristic is deposited on the whole structure which the diffusion barrier and the lower electrode pattern have been completed a. hich temperature in oxygen containing ambient. Namely, the film  29  is deposited by a metal organic chemical vapor deposition(MOCVD) method at temperature of 400° C.-650° C., the thickness of the film is preferable in range of 100Å-1000Å. When the (Ba, Sr)TiC 3  film  29  is deposited at high temperature in oxygen containing ambient, the oxygen dif. used through the first Pt film  28  reacts with the Ir film  27 , whereby, an IrO 2  Gilm  30  is formed on the interlaver of the Ir film  27  and the Pt film  28 . Thus, it can prevent the TiN film  24  from being oxidized.  
         [0018]    Then, a second Pt film  31  is formed on the (Ba, Sr)Tio 3  film  29 , after that the second Pt film  31  and the (BEa, Sr)Ti 3 . film  29  is patterned to form a capacitor.  
         [0019]    As described above, in forminc a dielectric layer having a high dielectric characteristic or. a lower electrode, the lower electrode is formed from a double layer consistinc of a Pt film and Ir film. Accordingly, as the oxycen diffuses throuoh the Pt film reacts with the Ir film, the nitride system film under the Ir film can be prevented from being nitrated, also, as the Pt film is located at interlayer of the dielectric layer and iridium oxide, leak current does not increase, so reliability of a oevice is improved.  
         [0020]    Although a preferred embodiment of the present invention has been illustrated and described, various alternatives, modifications and equivalents may be used. Thereore, the foregoing description should not be taken as limiting the scope of the present invention which is defined by the appended claims.