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.

1 . A layered ferromagnetic structure comprising: 
 a first ferromagnetic layer positioned over a substrate;    a second ferromagnetic layer positioned over said first ferromagnetic layer; and    a first non-magnetic layer placed between said first and second ferromagnetic layers,    wherein a top surface of said first ferromagnetic layer is in contact with said first non-magnetic layer, and    wherein said first ferromagnetic layer includes a first orientation control buffer that exhibits an effect of enhancing crystalline orientation of a film formed thereon.    
     
     
         2 . The layered ferromagnetic structure according to  claim 1 , wherein said first ferromagnetic layer further includes: 
 a first ferromagnetic film; and    a second ferromagnetic film positioned over said first ferromagnetic film, and    wherein said first orientation control buffer is placed between said first and second ferromagnetic films and designed to provide ferromagnetic coupling between said first and second ferromagnetic films.    
     
     
         3 . The layered ferromagnetic structure according to  claim 2 , wherein said first orientation control buffer has a thickness of 1.0 nm or less.  
     
     
         4 . The layered ferromagnetic structure according to  claim 2 , wherein said first orientation control buffer 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.  
     
     
         5 . The layered ferromagnetic structure according to  claim 4 , wherein said first orientation control buffer has a thickness of 0.7 nm or less.  
     
     
         6 . The layered ferromagnetic structure according to  claim 2 , wherein said first orientation control buffer 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.  
     
     
         7 . The layered ferromagnetic structure according to  claim 2 , wherein said first orientation control buffer is formed to allow said first and second ferromagnetic films to be partially contacted with each other.  
     
     
         8 . The layered ferromagnetic structure according to  claim 2 , wherein said first orientation control buffer 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.  
     
     
         9 . The layered ferromagnetic structure according to  claim 8 , wherein a thickness of said first orientation control buffer is adjusted so that said first orientation control buffer exhibits ferromagnetic coupling between said first and second ferromagnetic films.  
     
     
         10 . The layered ferromagnetic structure according to  claim 2 , wherein the closest-packed face of said second ferromagnetic film highly orients perpendicular to the film plane compared to said first ferromagnetic film.  
     
     
         11 . The layered ferromagnetic structure according to  claim 10 , wherein said second ferromagnetic film has a FCC structure, and exhibits higher FCC (111) orientation, compared to said first ferromagnetic film.  
     
     
         12 . The layered ferromagnetic structure according to  claim 10 , wherein said second ferromagnetic film has a BCC structure, and exhibits higher BCC (110) orientation, compared to said first ferromagnetic film.  
     
     
         13 . The layered ferromagnetic structure according to  claim 10 , wherein said second ferromagnetic film has an HCP structure, and exhibits higher HCP (001) orientation, compared to said first ferromagnetic film.  
     
     
         14 . The layered ferromagnetic structure according to  claim 11 , 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.    
     
     
         15 . The layered ferromagnetic structure according to  claim 12 , 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.    
     
     
         16 . The layered ferromagnetic structure according to  claim 1 , wherein said first orientation control buffer is ferromagnetic, and formed directly on an amorphous layer, and 
 wherein said first ferromagnetic layer includes a ferromagnetic film formed on said first orientation control buffer.    
     
     
         17 . The layered ferromagnetic structure according to  claim 1 , wherein said first ferromagnetic layer includes a ferromagnetic film, 
 wherein said first orientation control buffer is ferromagnetic and formed on said ferromagnetic film, and    wherein said first non-magnetic layer is formed on said first orientation control buffer.    
     
     
         18 . The layered ferromagnetic structure according to  claim 2 , wherein said first orientation control buffer 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.    
     
     
         19 . The layered ferromagnetic structure according to  claim 16 , wherein said first orientation control buffer 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.    
     
     
         20 . The layered ferromagnetic structure according to  claim 17 , wherein said first orientation control buffer 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.    
     
     
         21 . The layered ferromagnetic structure according to  claim 18 , 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 orientation control buffer ranges from 5 to 25 atomic %.    
     
     
         22 . The layered ferromagnetic structure according to  claim 1 , wherein said second ferromagnetic layer includes: 
 a third ferromagnetic film;    a fourth ferromagnetic film positioned over said third ferromagnetic film; and    a second orientation control buffer placed between said third and fourth ferromagnetic films.    
     
     
         23 . The layered ferromagnetic structure according to  claim 22 , wherein said second orientation control buffer is amorphous.  
     
     
         24 . The layered ferromagnetic structure according to  claim 23 , wherein said second orientation control buffer is formed of ferromagnetic material.  
     
     
         25 . The layered ferromagnetic structure according to  claim 23 , wherein said second ferromagnetic layer further includes a third orientation control buffer placed between said second orientation control buffer and said fourth ferromagnetic film, and 
 wherein said third orientation control buffer is configured to enhance crystalline orientation of said fourth ferromagnetic film.    
     
     
         26 . The layered ferromagnetic structure according to  claim 1 , wherein said second ferromagnetic layer includes: 
 an amorphous ferromagnetic film formed on said first non-magnetic layer;    a fourth orientation control buffer formed on said amorphous ferromagnetic film; and    an additional ferromagnetic film,    wherein said fourth orientation control buffer is configured to enhance crystalline orientation of said additional ferromagnetic film.    
     
     
         27 . The layered ferromagnetic structure according to  claim 1 , wherein said second ferromagnetic layer includes: 
 a third ferromagnetic film;    a fourth ferromagnetic film;    a fifth orientation control buffer placed between said third and fourth ferromagnetic films,    wherein said third ferromagnetic film is plasma-treated, and    wherein said fifth orientation control buffer is configured to enhance crystalline orientation of said fourth ferromagnetic film.    
     
     
         28 . The layered ferromagnetic structure according to  claim 22 , further comprising: 
 a second non-magnetic layer formed on said second ferromagnetic layer; and    a third ferromagnetic layer formed on said second non-magnetic layer.    
     
     
         29 . The layered ferromagnetic structure according to  claim 28 , wherein said third ferromagnetic layer includes a sixth orientation control buffer that is amorphous.  
     
     
         30 . The layered ferromagnetic structure according to  claim 29 , wherein said third ferromagnetic layer further includes: 
 a fifth ferromagnetic film; and    a sixth ferromagnetic film positioned over said fifth ferromagnetic film, and    wherein said sixth orientation control buffer is placed between said fifth and sixth ferromagnetic films.    
     
     
         31 . The layered ferromagnetic structure according to  claim 28 , wherein said third ferromagnetic layer includes: 
 a fifth ferromagnetic film;    a sixth ferromagnetic film; and    a fifth orientation control buffer placed between said fifth and sixth ferromagnetic films,    wherein said fifth ferromagnetic film is plasma-treated, and    wherein said fifth orientation control buffer is configured to enhance crystalline orientation of said sixth ferromagnetic film.    
     
     
         32 . The layered ferromagnetic structure according to  claim 1 , further comprising: 
 a second non-magnetic layer formed on said second magnetic layer; and    a third ferromagnetic layer formed on said second non-magnetic layer,    wherein said second ferromagnetic layer is formed of ferromagnetic material doped with non-magnetic material.    
     
     
         33 . The layered ferromagnetic structure according to  claim 32 , wherein said third ferromagnetic layer is formed of ferromagnetic material doped with non-magnetic material.  
     
     
         34 . The layered ferromagnetic structure according o  claim 1 , wherein said first non-magnetic layer is configured to provide antiferromagnetic coupling between said first and second ferromagnetic layers.  
     
     
         35 . The layered ferromagnetic structure according to  claim 28 , wherein said first non-magnetic layer is configured to provide antiferromagnetic coupling between said first and second ferromagnetic layers, and 
 wherein said second non-magnetic layer is configured to provide antiferromagnetic coupling between said second and third ferromagnetic layers.    
     
     
         36 . A layered ferromagnetic structure comprising: 
 a first ferromagnetic layer;    a second ferromagnetic layer; and    a first non-magnetic layer placed between said first and second ferromagnetic layers,    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;  
 a second ferromagnetic film ferromagnetically coupled with said first ferromagnetic film,  
   wherein said second ferromagnetic film is positioned between said first ferromagnetic film and said first non-magnetic layer, and    wherein crystalline structure of said second ferromagnetic film is different from that of said first ferromagnetic film.    
     
     
         37 . The layered ferromagnetic structure according to  claim 36 , wherein said crystalline orientation of said second ferromagnetic film is higher than that of said first ferromagnetic film.  
     
     
         38 . The layered ferromagnetic structure according to  claim 37 , wherein a bottom surface of said first ferromagnetic film is in contact with an amorphous film.  
     
     
         39 . The layered ferromagnetic structure according to  claim 38 , wherein said second ferromagnetic layer includes: 
 a third ferromagnetic film, and    a fourth ferromagnetic film ferromagnetically coupled with said third ferromagnetic film.    
     
     
         40 . The layered ferromagnetic structure according to  claim 39 , wherein said fourth ferromagnetic film exhibits poorer crystalline orientation than that of said third ferromagnetic film.  
     
     
         41 . The layered ferromagnetic structure according to  claim 40 , wherein said fourth ferromagnetic film is plasma-treated.  
     
     
         42 . The layered ferromagnetic structure according to  claim 40 , further comprising: 
 a second non-magnetic layer formed on said second ferromagnetic; and    a third ferromagnetic layer formed on said second non-magnetic layer.    
     
     
         43 . The layered ferromagnetic structure according to  claim 42 , wherein said third ferromagnetic layer includes: 
 a fifth ferromagnetic film; and    a sixth ferromagnetic film ferromagnetically coupled with said fifth ferromagnetic film.    
     
     
         44 . The layered ferromagnetic structure according to  claim 43 , wherein said sixth ferromagnetic film exhibits poorer crystalline orientation than that of said fifth ferromagnetic film.  
     
     
         45 . The layered ferromagnetic structure according to  claim 43 , wherein said sixth ferromagnetic film is plasma-treated.  
     
     
         46 . The layered ferromagnetic structure according to  claim 36 , wherein said second ferromagnetic film exhibits poorer crystalline orientation than that of said first ferromagnetic film.  
     
     
         47 . The layered ferromagnetic structure according to  claim 36 , wherein said first non-magnetic layer is configured to provide antiferromagnetic coupling between said first and second ferromagnetic layers.  
     
     
         48 . The layered ferromagnetic structure according to  claim 42 , wherein said first non-magnetic layer is configured to provide antiferromagnetic coupling between said first and second ferromagnetic layers, and 
 wherein said second non-magnetic layer is configured to provide antiferromagnetic coupling between said second and third ferromagnetic layers.    
     
     
         49 . An MTJ element comprising: 
 a fixed magnetic layer positioned over a substrate;    a free magnetic layer positioned over said substrate;    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 tunnel barrier 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, and    wherein said first ferromagnetic layer includes a first orientation control buffer that exhibits an effect of enhancing crystalline orientation of a film formed thereon.    
     
     
         50 . The MTJ element according to  claim 49  wherein said first ferromagnetic layer further includes: 
 a first ferromagnetic film; and    a second ferromagnetic film positioned over said first ferromagnetic film, and    wherein said first orientation control buffer is placed between said first and second ferromagnetic films and designed to provide ferromagnetic coupling between said first and second ferromagnetic films.    
     
     
         51 . The MTJ element according to  claim 49 , wherein said first orientation control buffer is ferromagnetic, and formed directly on said tunnel barrier layer, and 
 wherein said first ferromagnetic layer includes a ferromagnetic film formed on said first orientation control buffer.    
     
     
         52 . The MTJ element according to  claim 49 , wherein said first ferromagnetic layer further includes a ferromagnetic film formed on said tunnel barrier layer, and 
 wherein said first orientation control buffer is ferromagnetic and formed on said ferromagnetic film, and    wherein said first non-magnetic layer is formed on said first orientation control buffer.    
     
     
         53 . The MTJ element according to  claim 49 , wherein said second ferromagnetic layer includes a second orientation control buffer which is amorphous.  
     
     
         54 . The MTJ element according to  claim 53 , wherein said second ferromagnetic layer further includes: 
 a third ferromagnetic film; and    a fourth ferromagnetic film positioned over said third ferromagnetic film, and    wherein said second orientation control buffer is placed between said third and fourth ferromagnetic films.    
     
     
         55 . The MTJ element according to  claim 54 , wherein said second orientation control buffer is formed of ferromagnetic material.  
     
     
         56 . The MTJ element according to  claim 53 , wherein said second ferromagnetic layer includes a third orientation control buffer placed between said second orientation control buffer and said fourth ferromagnetic film, and 
 wherein said third orientation control buffer is configured to enhance crystalline orientation of said fourth ferromagnetic film.    
     
     
         57 . The MTJ element according to  claim 49 , wherein said second ferromagnetic layer includes: 
 an amorphous ferromagnetic film formed on said first non-magnetic layer;    a fourth orientation control buffer formed on said amorphous ferromagnetic film; and    an additional ferromagnetic film formed on said fourth orientation control buffer,    wherein said fourth orientation control buffer is configured to enhance crystalline orientation of said additional ferromagnetic film.    
     
     
         58 . An MTJ element comprising: 
 a fixed magnetic layer;    a tunnel barrier layer formed on a top surface of said fixed magnetic layer; and    a free magnetic layer formed on a top surface of said tunnel barrier layer;    wherein said fixed magnetic layer includes:    first and second ferromagnetic layers;    a first non-magnetic layer placed between said first and second ferromagnetic layers,    wherein a top surface of said first ferromagnetic layer is in contact with said first non-magnetic layer, and    wherein said first ferromagnetic layer includes an orientation control buffer that exhibits an effect of enhancing crystalline orientation of a film formed thereon.    
     
     
         59 . An MTJ element comprising: 
 a free magnetic layer;    a tunnel barrier layer formed on a top surface of said free magnetic layer; and    a fixed magnetic layer formed on a top surface of said tunnel barrier layer;    wherein said fixed magnetic layer includes:    first and second ferromagnetic layers;    a first non-magnetic layer placed between said first and second ferromagnetic layers,    wherein a top surface of said first ferromagnetic layer is in contact with said first non-magnetic layer, and    wherein said first ferromagnetic layer includes an orientation control buffer that exhibits an effect of enhancing crystalline orientation of a film formed thereon.    
     
     
         60 . A method for manufacturing a layered ferromagnetic structure comprising: 
 forming a first ferromagnetic layer;    forming a first non-magnetic layer on said first ferromagnetic layer;    forming a second ferromagnetic layer on said first non-magnetic layer;    forming a second non-magnetic layer on said second ferromagnetic layer; and    forming a third ferromagnetic layer on said second non-magnetic layer,    wherein said forming said first ferromagnetic layer includes:    forming a first orientation control buffer within any portion of said first ferromagnetic layer, said first orientation control buffer having an effect of enhancing crystalline orientation of a film formed thereon,    wherein said forming said second ferromagnetic layer includes:    forming a third ferromagnetic film;    subjecting said third ferromagnetic film to plasma-treatment; and    forming a fourth ferromagnetic film over said third ferromagnetic film, said fourth ferromagnetic film being ferromagnetically coupled with said third ferromagnetic film.    
     
     
         61 . A method for manufacturing a layered ferromagnetic structure comprising: 
 forming a first ferromagnetic layer;    forming a first non-magnetic layer on said first ferromagnetic layer;    forming a second ferromagnetic layer on said first non-magnetic layer;    forming a second non-magnetic layer on said second ferromagnetic layer; and    forming a third ferromagnetic layer on said second non-magnetic layer,    wherein said forming said first ferromagnetic layer includes:    forming a first orientation control buffer within any portion of said first ferromagnetic layer, said first orientation control buffer having an effect of enhancing crystalline orientation of a film formed thereon,    wherein said second ferromagnetic layer is formed through a sputtering method using sputtering gas to which oxygen or nitrogen is added.    
     
     
         62 . A method according to  claim 61 , wherein said third ferromagnetic layer is formed through a sputtering method using sputtering gas to which oxygen or nitrogen is added.  
     
     
         63 . A method for manufacturing a layered ferromagnetic structure comprising: 
 forming a first ferromagnetic layer;    forming a first non-magnetic layer on said first ferromagnetic layer;    forming a second ferromagnetic layer on said first non-magnetic layer;    forming a second non-magnetic layer on said second ferromagnetic layer; and    forming a third ferromagnetic layer on said second non-magnetic layer,    wherein said forming said first ferromagnetic layer includes:    forming a first orientation control buffer within any portion of said first ferromagnetic layer, said first orientation control buffer having an effect of enhancing crystalline orientation of a film formed thereon,    wherein said second ferromagnetic layer is formed of ferromagnetic material doped with non-magnetic material.    
     
     
         64 . The method according to  claim 63 , wherein said third ferromagnetic layer is formed of ferromagnetic material doped with non-magnetic material.