Magnetoresistance device including layered ferromagnetic structure, and method of manufacturing the same

Abstract

A layered ferromagnetic structure is composed of a first ferromagnetic layer positioned over a substrate; a second ferromagnetic layer positioned over the first ferromagnetic layer; and a first non-magnetic layer placed between the first and second ferromagnetic layers. The top surface of the first ferromagnetic layer is in contact with the first non-magnetic layer. The first ferromagnetic layer includes a first orientation control buffer that exhibits an effect of enhancing crystalline orientation of a film formed thereon.

What is claimed is: 
     
         1 . An MTJ element, comprising:
 a fixed magnetic layer;   a free magnetic layer;   a tunnel barrier layer placed between said fixed and free magnetic layers,   wherein one of said fixed and free magnetic layers is positioned over said tunnel barrier layer, and   wherein said one of said fixed and free magnetic layers includes:
 a first ferromagnetic layer formed on said tunnel barrier layer; 
 a first non-magnetic layer formed on said first magnetic layer; and 
 a second ferromagnetic layer formed on said first non-magnetic layer, 
   wherein a top surface of said first ferromagnetic layer is in contact with said first non-magnetic layer,   wherein said first ferromagnetic layer includes:
 a first ferromagnetic film formed on said tunnel barrier layer; 
 a second ferromagnetic film positioned over said first ferromagnetic film, and 
 a first buffer film placed between said first and second ferromagnetic films and designed to provide ferromagnetic coupling between said first and second ferromagnetic films, and 
   wherein said second ferromagnetic layer includes:   a third ferromagnetic film formed on said first non-magnetic layer; and   a fourth ferromagnetic film positioned over said third ferromagnetic film, and   a second buffer film placed between said third and fourth ferromagnetic films and designed to provide ferromagnetic coupling between said third and fourth ferromagnetic films.   
     
     
         2 . The MTJ element according to  claim 1 , wherein said first buffer film is formed of material selected from a group consisting of tantalum (Ta), ruthenium (Ru), niobium (Nb), vanadium (V), osmium (Os), rhodium (Rh), iridium (Ir), titanium (Ti), zirconium (Zr), hafnium (Hf), copper (Cu), silver (Ag), gold (Au), chromium (Cr), molybdenum (Mo), tungsten (W), aluminum (Al), magnesium (Mg), silicon (Si), yttrium (Y), cerium (Ce), palladium (Pd), rhenium (Re), alloys thereof, and compounds thereof. 
     
     
         3 . The MTJ element according to  claim 1 , wherein said first buffer film is formed of material selected from a group consisting of tantalum (Ta), niobium (Nb), zirconium (Zr), hafnium (Hf), molybdenum (Mo), tungsten (W), alloys thereof, and compounds thereof. 
     
     
         4 . The MTJ element according to  claim 1 , wherein said first buffer film is formed of material selected from a group consisting of ruthenium (Ru), chromium (Cr), rhenium (Re), rhodium (Rh), iridium (Ir), yttrium (Y), silver (Ag), copper (Cu), alloys thereof, and compounds thereof. 
     
     
         5 . The MTJ element according to  claim 1 , wherein said second buffer film is formed of tantalum or ruthenium. 
     
     
         6 . The MTJ element according to  claim 1 , wherein said second buffer film is amorphous. 
     
     
         7 . The MTJ element according to  claim 6 , wherein said second buffer film is non-magnetic. 
     
     
         8 . The MTJ element according to  claim 7 , wherein said second buffer film is formed of SiN, AlN, or AlOx. 
     
     
         9 . The MTJ element according to  claim 6 , wherein said second buffer film is ferromagnetic. 
     
     
         10 . The MTJ element according to  claim 9 , wherein said second buffer film is formed of NiFeTaOx, NiFeTaNx, CoFeB or NiFeB. 
     
     
         11 . The MTJ element according to  claim 6 , wherein said second ferromagnetic layer further includes a third buffer film placed between said second buffer film and said fourth ferromagnetic film. 
     
     
         12 . The MTJ element according to  claim 11 , wherein said third buffer film is formed of tantalum or ruthenium. 
     
     
         13 . The MTJ element according to  claim 1 , wherein said third ferromagnetic film is amorphous. 
     
     
         14 . The MTJ element according to  claim 13 , wherein said third buffer film is formed of tantalum or ruthenium. 
     
     
         15 . The MTJ element according to  claim 14 , wherein said third ferromagnetic film is formed of NiFeTaOx, NiFeTaNx, CoFeB or NiFeB. 
     
     
         16 . The MTJ element according to  claim 1 , wherein said third ferromagnetic film is plasma-treated. 
     
     
         17 . The MTJ element according to  claim 16 , wherein said second buffer film is formed of tantalum or ruthenium. 
     
     
         18 . The MTJ element according to  claim 1 , wherein said first buffer film has a thickness of 1.0 nm or less. 
     
     
         19 . The MTJ element according to  claim 2 , wherein said first buffer film has a thickness of 0.7 nm or less. 
     
     
         20 . The MTJ element according to  claim 1 , wherein said first buffer film is formed to allow said first and second ferromagnetic films to be partially contacted with each other. 
     
     
         21 . The MTJ element according to  claim 4 , wherein a thickness of said first buffer film is adjusted so that said first buffer film exhibits ferromagnetic coupling between said first and second ferromagnetic films. 
     
     
         22 . The MTJ element according to  claim 1 , wherein the closest-packed face of said second ferromagnetic film is configured with a higher orientation perpendicular to the film plane compared to said first ferromagnetic film. 
     
     
         23 . The MTJ element according to  claim 22 , wherein said second ferromagnetic film has a FCC structure, and exhibits higher FCC (111) orientation, compared to said first ferromagnetic film. 
     
     
         24 . The MTJ element according to  claim 22 , wherein said second ferromagnetic film has a BCC structure, and exhibits higher BCC (110) orientation, compared to said first ferromagnetic film. 
     
     
         25 . The MTJ element according to  claim 22 , wherein said second ferromagnetic film has an HCP structure, and exhibits higher HCP (001) orientation, compared to said first ferromagnetic film. 
     
     
         26 . The MTJ element according to  claim 23 , wherein said second ferromagnetic film is formed of material selected from a group consisting of nickel, iron, cobalt, and alloys thereof, and
 wherein said first non-magnetic layer is formed of ruthenium or alloy thereof.   
     
     
         27 . The MTJ element according to  claim 24 , wherein said second ferromagnetic film is formed of material selected from a group consisting of nickel, iron, cobalt, and alloys thereof, and
 wherein said first non-magnetic layer is formed of ruthenium or alloy thereof.   
     
     
         28 . The MTJ element according to  claim 1 , wherein said first buffer film is configured to be ferromagnetic, including:
 ferromagnetic material; and   at least one material selected from a group consisting of tantalum, niobium, zirconium, hafnium, molybdenum, and tungsten.   
     
     
         29 . The MTJ element according to  claim 28 , wherein said ferromagnetic material is NiFe,
 wherein said at least one material is tantalum or zirconium, and   wherein a tantalum or zirconium content of said first buffer film ranges from 5 to 25 atomic %.