Method for fabricating dielectric capacitor

Abstract

Disclosed is a method for fabricating a dielectric capacitor that comprises a lover electrode made of at least one of Ir, Pd, Ru and Rh or containing at least one of those elements, a dielectric film of a ferroelectric or high dielectric substance as formed on the lower electrode, and an upper electrode as formed on the dielectric film. The method comprises a first heat treatment step for completing the formation of the dielectric film in an oxygen-containing vapor atmosphere followed by a second heat treatment step to be effected in a nitrogen or inert gas atmosphere at a temperature not lower than that for the first heat treatment. The method solves the problem with the dielectric layer of a ferroelectric substance of SBT or the like, of which the characteristics are worsened after forming gas annealing especially when the dielectric layer is formed on a lower electrode of a noble metal except platinum and gold.

What is claimed is:  
     
         1 . A method for fabricating a dielectric capacitor that comprises; 
 a lower electrode made of at least one of iridium, palladium, ruthenium and rhodium or containing at least one of those elements,    a dielectric film of a ferroelectric or high dielectric substance as formed on said lower electrode, and    an upper electrode as formed on said dielectric film;    the method comprising a first heat treatment step for completing the formation of said dielectric film in an oxygen-containing vapor atmosphere followed by a second heat treatment step to be effected in a nitrogen or inert gas atmosphere.    
     
     
         2 . The method for fabricating a dielectric capacitor as claimed in    claim 1   , wherein said second heat treatment is effected at a temperature not lower than that for said first heat treatment.  
     
     
         3 . A method for fabricating a dielectric capacitor that comprises; 
 a lower electrode made of at least one of iridium, palladium, ruthenium and rhodium or containing at least one of those elements,    a dielectric film of a ferroelectric or high dielectric substance as formed on said lower electrode, and    an upper electrode as formed on said dielectric film,    the method comprising a heat treatment step for completing the formation of said dielectric film in an oxygen-containing vapor atmosphere followed by a reduction step for reducing the oxide having been formed in said lower electrode through oxidation in said heat treatment step.    
     
     
         4 . A method for fabricating a dielectric capacitor that comprises; 
 a lower electrode made of at least one of iridium, palladium, ruthenium and rhodium or containing at least one of those elements,    a dielectric film of a ferroelectric or high dielectric substance as formed on said lower electrode, and    an upper electrode as formed on said dielectric film,    the method comprising a first heat treatment step for completing the formation of said dielectric film in an oxygen-containing vapor atmosphere followed by a reduction step for reducing the oxide having been formed in said lower electrode through oxidation in said first heat treatment step, and    a second heat treatment step to be effected after the reduction step in a nitrogen or inert gas atmosphere.    
     
     
         5 . The method for producing a dielectric capacitor as claimed in    claim 4   , which additionally comprises another heat treatment step for oxygen supply to be effected after said reduction step and before said second heat treatment step in an oxygen-containing atmosphere at a temperature lower than that at which the substance having been reduced in said reduction step may be oxidized.  
     
     
         6 . The method for producing a dielectric capacitor as claimed in    claim 1   , wherein a diffusion-preventing layer that comprises; 
 iridium,    at least one of hafnium, tantalum, zirconium, niobium, vanadium, molybdenum, tungsten, yttrium and rare earth metal elements, and    oxygen,    is formed below said lower electrode.    
     
     
         7 . The method for producing a dielectric capacitor as claimed in    claim 2   , wherein a diffusion-preventing layer that comprises; 
 iridium,    at least one of hafnium, tantalum, zirconium, niobium, vanadium, molybdenum, tungsten, yttrium and rare earth metal elements, and    oxygen,    is formed below said lower electrode.    
     
     
         8 . The method for producing a dielectric capacitor as claimed in    claim 3   , wherein a diffusion-preventing layer that comprises; 
 iridium,    at least one of hafnium, tantalum, zirconium, niobium, vanadum, molybdenum, tungsten, yttrium and rare earth metal elements, and    oxygen,    is formed below said lower electrode.    
     
     
         9 . The method for producing a dielectric capacitor as claimed in    claim 4   , wherein a diffusion-preventing layer that comprises; 
 iridium,    at least one of hafnium, tantalum, zirconium, niobium, vanadium, molybdenum, tungsten, yttrium and rare earth metal elements, and    oxygen,    is formed below said lower electrode.    
     
     
         10 . The method for producing a dielectric capacitor as claimed in    claim 5   , wherein a diffusion-preventing layer that comprises; 
 iridium,    at least one of hafnium, tantalum, zirconium, niobium, vanadium, molybdenum, tungsten, yttrium and rare earth metal elements, and    oxygen,    is formed below said lower electrode.    
     
     
         11 . The method for producing a dielectric capacitor as claimed in    claim 1   , wherein said dielectric film is of a bismuth phyllo-perovskite structured, ferroelectric substance.  
     
     
         12 . The method for producing a dielectric capacitor as claimed in    claim 2   , wherein said dielectric film is of a bismuth phyllo-perovskite structured, ferroelectric substance.  
     
     
         13 . The method for producing a dielectric capacitor as claimed in    claim 3   , wherein said dielectric film is of a bismuth phyllo-perovskite structured, ferroelectric substance.  
     
     
         14 . The method for producing a dielectric capacitor as claimed in    claim 4   , wherein said dielectric film is of a bismuth phyllo-perovskite structured, ferroelectric substance.  
     
     
         15 . The method for producing a dielectric capacitor as claimed in    claim 5   , wherein said dielectric film is of a bismuth phyllo-perovskite structured, ferroelectric substance.  
     
     
         16 . The method for producing a dielectric capacitor as claimed in    claim 11   , wherein said ferroelectric substance comprises essential crystalline layers of a substance to be represented by the following chemical formula and said crystalline layers contain oxides of at least one of bismuth, tantalum and niobium:  
       Bi x (Sr,Ca,Ba) y (Ta,Nb) 2 O z   
       wherein 1.70≦x≦2.50, 0.60≦y≦1.20, z=9±d, 0≦d≦1.0.  
     
     
         17 . The method for producing a dielectric capacitor as claimed in    claim 12   , wherein said ferroelectric substance comprises essential crystalline layers of a substance to be represented by the following chemical formula and said crystalline layers contain oxides of at least one of bismuth, tantalum and niobium:  
       Bi x (Sr,Ca,Ba) y (Ta,Nb) 2 O z   
       wherein 1.70≦x≦2.50, 0.60≦y≦1.20, z=9±d, 0≦d≦1.0.  
     
     
         18 . The method for producing a dielectric capacitor as claimed in    claim 13   , wherein said ferroelectric substance comprises essential crystalline layers of a substance to be represented by the following chemical formula and said crystalline layers contain oxides of at least one of bismuth, tantalum and niobium:  
       Bi x (Sr,Ca,Ba) y (Ta,Nb) 2 O z   
       wherein 1.70≦x≦2.50, 0.60≦y≦1.20, z=9±d, 0≦d≦1.0.  
     
     
         19 . The method for producing a dielectric capacitor as claimed in    claim 14   , wherein said ferroelectric substance comprises essential crystalline layers of a substance to be represented by the following chemical formula and said crystalline layers contain oxides of at least one of bismuth, tantalum and niobium:  
       Bi x (Sr,Ca,Ba) y (Ta,Nb) 2 O z   
       wherein 1.70≦x≦2.50, 0.60≦y≦1.20, z=9±d, 0≦d≦1.0.  
     
     
         20 . The method for producing a dielectric capacitor as claimed in    claim 15   , wherein said ferroelectric substance comprises essential crystalline layers of a substance to be represented by the following chemical formula and said crystalline layers contain oxides of at least one of bismuth, tantalum and niobium:  
       Bi x (Sr,Ca,Ba) y (Ta,Nb) 2 O z   
       wherein 1.70≦x≦2.50, 0.60≦y≦1.20, z=9±d, 0≦d≦1.0.  
     
     
         21 . The method for producing a dielectric capacitor as claimed in    claim 11   , wherein said ferroelectric substance comprises essential crystalline layers of a substance to be represented by the following chemical formula and said crystalline layers contain oxides of at least one of bismuth and tantalum:  
       Bi x Sr y Ta 2 O z   
       wherein 1.70≦x≦2.50, 0.60≦y≦1.20, z=9±d, 0≦d≦1.0.  
     
     
         22 . The method for producing a dielectric capacitor as claimed in    claim 12   , wherein said ferroelectric substance comprises essential crystalline layers of a substance to be represented by the following chemical formula and said crystalline layers contain oxides of at least one of bismuth and tantalum:  
       Bi x Sr y Ta 2 O z   
       wherein 1.70≦x≦2.50, 0.60≦y≦1.20, z=9±d, 0≦d≦1.0.  
     
     
         23 . The method for producing a dielectric capacitor as claimed in    claim 13   , wherein said ferroelectric substance comprises essential crystalline layers of a substance to be represented by the following chemical formula and said crystalline layers contain oxides of at least one of bismuth and tantalum:  
       Bi x Sr y Ta 2 O z   
       wherein 1.70≦x≦2.50, 0.60≦y≦1.20, z=9±d, 0≦d≦1.0.  
     
     
         24 . The method for producing a dielectric capacitor as claimed in    claim 14   , wherein said ferroelectric substance comprises essential crystalline layers of a substance to be represented by the following chemical formula and said crystalline layers contain oxides of at least one of bismuth and tantalum:  
       Bi x Sr y Ta 2 O z   
       wherein 1.70≦x≦2.50, 0.60≦y≦1.20, z=9±d, 0≦d≦1.0.  
     
     
         25 . The method for producing a dielectric capacitor as claimed in    claim 15   , wherein said ferroelectric substance comprises essential crystalline layers of a substance to be represented by the following chemical formula and said crystalline layers contain oxides of at least one of bismuth and tantalum:  
       Bi x Sr y Ta 2 O z   
       wherein 1.70≦x≦2.50, 0.60≦y≦1.20, z=9±d, 0≦d≦1.0.