Ferroelectric film, method of manufacturing the same, ferroelectric memory and piezoelectric device

Abstract

A ferroelectric film wherein 5 to 40 mol % in total of at least one of Nb, V, and W is included in the B site of a Pb(Zr,Ti)O 3 ferroelectric which includes at least four-fold coordinated Si 4+ or Ge 4+ in the A site ion of a ferroelectric perovskite material in an amount of 1% or more. This enables to significantly improve reliability of the ferroelectric film.

1 . A method of manufacturing a ferroelectric film including Pb(Zr,Ti)O 3 , the method comprising: 
 using a sol-gel solution for forming Pb(Zr,Ti)O 3  which includes at least four-fold coordinated Si 4+  or Ge 4+  in the Pb site ion in an amount of 1% or more.    
     
     
         2 . A method of manufacturing a ferroelectric film including Pb(Zr,Ti)O 3 , the method comprising: 
 using a sol-gel solution for forming Pb(Zr,Ti)O 3  which includes at least four-fold coordinated Si 4+  or Ge 4+  in the Pb site ion in an amount of 1% or more, wherein a mixed solution prepared by mixing a sol-gel solution for forming PbZrO 3  which includes at least four-fold coordinated Si 4+  or Ge 4+  in the Pb site ion in an amount of 1% or more with a sol-gel solution for forming PbTiO 3  which includes at least four-fold coordinated Si 4+  or Ge 4+  in the Pb site ion in an amount of 1% or more is used as the sol-gel solution for forming Pb(Zr,Ti)O 3 .    
     
     
         3 . A method of manufacturing a ferroelectric film including Pb(Zr,Ti)O 3 , the method comprising: 
 using a sol-gel solution for forming Pb(Zr,Ti)O 3  in which the amount of Pb ranges from 90 to 120% of the stoichiometric composition of Pb(Zr,Ti)O 3 .    
     
     
         4 . A method of manufacturing a ferroelectric film including Bi 4 Ti 3 O 12 , the method comprising: 
 using a sol-gel solution for forming Bi 4 Ti 3 O 12  which includes at least four-fold coordinated Si 4+  or Ge 4+  in the Bi site ion in an amount of 1% or more.    
     
     
         5 . A method of manufacturing a ferroelectric film including Bi 4 Ti 3 O 12 , the method comprising: 
 using a mixed solution prepared by mixing a solution prepared by mixing a sol-gel solution for forming Bi 2 O 3  with a sol-gel solution for forming TiO 2  at a molar ratio of 2:3 with a sol-gel solution for forming a dielectric shown by X 2 SiO 5 , X 4 Si 3 O 12 , X 2 GeO 5 , or X 4 Ge 3 O 12  (wherein X represents Bi 3+ , Fe 3+ , Sc 3+ , Y 3+ , La 3+ , Ce 3+ , Pr 3+ , Nd 3+ , Pm 3+ , Sm 3+ , Eu 3+ , Gd 3+ , Tb 3+ , Dy 3+ , Ho 3+ , Er 3+ , Tm 3+ , Yb 3+ , or Lu 3+ ) so that Si 4+  or Ge 4+  is included in an amount of 1 mol % or more.    
     
     
         6 . A method of manufacturing a ferroelectric film including Bi 4 Ti 3 O 12 , the method comprising: 
 using a sol-gel solution for forming Bi 4 Ti 3 O 12  in which an excess amount of Bi ranges from 90 to 120% of the stoichiometric composition of Bi 4 Ti 3 O 12 .