Magnetic tunnel junction device and memory device including the same

Abstract

The output voltage of an MRAM is increased by means of an Fe( 001 )/MgO( 001 )/Fe( 001 ) MTJ device, which is formed by microfabrication of a sample prepared by the following steps. A single-crystalline MgO ( 001 ) substrate 11 is prepared. An epitaxial Fe( 001 ) lower electrode (a first electrode) 17 with the thickness of 50 nm is grown on a MgO( 001 ) seed layer 15 at room temperature, followed by annealing under ultrahigh vacuum (2×10 −8 Pa) and at 350° C. A MgO( 001 ) barrier layer 21 with the thickness of 2 nm is epitaxially formed on the Fe( 001 ) lower electrode (the first electrode) at room temperature, using a MgO electron-beam evaporation. A Fe( 001 ) upper electrode (a second electrode) with the thickness of 10 nm is then formed on the MgO( 001 ) barrier layer 21 at room temperature. This is successively followed by the deposition of a Co layer 21 with the thickness of 10 nm on the Fe( 001 ) upper electrode (the second electrode) 23 . The Co layer 21 is provided so as to increase the coercive force of the upper electrode 23 in order to realize an antiparallel magnetization alignment.

1 . A method of manufacturing a magnetoresistive device comprising:
 preparing a substrate;   depositing a first amorphous ferromagnetic material layer on said substrate;   forming an amorphous MgO or MgO x  (0<x<1) layer on said first amorphous ferromagnetic material layer and then crystallizing said amorphous MgO or MgO x , (0<x<1) layer by annealing so as to form a tunnel barrier layer comprising a poly-crystalline MgO or MgO x  (0<x<1) layer in which ( 001 ) crystal plane is preferentially oriented; and   depositing a second amorphous ferromagnetic material layer on said tunnel barrier layer.   
     
     
         2 . A method of manufacturing a magnetoresistive device comprising:
 preparing a substrate;   depositing a first amorphous ferromagnetic material layer on said substrate;   forming an amorphous MgO or MgO x , (0<x<1) layer on said first amorphous ferromagnetic material layer and then crystallizing said amorphous MgO or MgO x  (0<x<1) layer by annealing so as to form a tunnel barrier layer comprising a poly-crystalline MgO or MgO x  (0<x<1) layer in which ( 001 ) crystal plane is preferentially oriented; and   depositing a second ferromagnetic material layer on said tunnel barrier layer.   
     
     
         3 . The method of manufacturing a magnetoresistive device according to  claim 1 , wherein
 said ferromagnetic material layers comprises CoFeB alloy.   
     
     
         4 . The method of manufacturing a magnetoresistive device according to  claim 2 , wherein
 said amorphous ferromagnetic material layer comprises CoFeB alloy.   
     
     
         5 . The method of manufacturing the magnetoresistive device according to  claim 1 , wherein the method further comprises an annealing step as to partially or entirely crystallize said amorphous ferromagnetic material layer or layers. 
     
     
         6 . The method of manufacturing the magnetoresistive device according to  claim 2 , wherein the method further comprises an annealing step as to partially or entirely crystallize said amorphous ferromagnetic material layer or layers. 
     
     
         7 . The method of manufacturing a magnetoresistive device according to  claim 5 , wherein
 said amorphous ferromagnetic material layer comprises CoFeB alloy.   
     
     
         8 . The method of manufacturing a magnetoresistive device according to  claim 6 , wherein
 said amorphous ferromagnetic material layer comprises CoFeB alloy.   
     
     
         9 . A method of manufacturing a magnetoresistive device comprising:
 preparing a substrate;   depositing a first amorphous ferromagnetic material layer on said substrate;   forming an amorphous magnesium oxide layer on said first amorphous ferromagnetic material layer and then crystallizing said amorphous magnesium oxide layer by annealing so as to form a tunnel barrier layer comprising a poly-crystalline magnesium oxide in which ( 001 ) crystal plane is preferentially oriented; and   depositing a second amorphous ferromagnetic material layer on said tunnel barrier layer.   
     
     
         10 . The method of manufacturing the magnetoresistive device according to  claim 5 , wherein the method further comprises an annealing step as to partially or entirely crystallize said amorphous ferromagnetic material layer or layers. 
     
     
         11 . A magnetoresistive device having a magnetic tunnel junction structure comprising:
 a first amorphous ferromagnetic material layer formed on a substrate;   a tunnel barrier layer on said first amorphous ferromagnetic material layer; and   a second ferromagnetic material layer formed on said tunnel barrier layer, wherein   said tunnel barrier layer comprises a poly-crystalline MgO x  (0<x<1) in which ( 001 ) crystal plane is preferentially oriented.   
     
     
         12 . The magnetoresistive device according to  claim 11 , wherein said first and second amorphous ferromagnetic material layers comprise CoFeB alloy. 
     
     
         13 . A magnetoresistive device having a magnetic tunnel junction structure comprising:
 a tunnel barrier layer deposited on an amorphous ferromagnetic material layer, wherein   said tunnel barrier layer comprises a poly-crystalline MgO x  (0<x<1) in which ( 001 ) crystal plane is preferentially oriented.   
     
     
         14 . The magnetoresistive device according to  claim 13 , wherein said first and second amorphous ferromagnetic material layers comprise CoFeB alloy. 
     
     
         15 . A magnetoresistive device having a magnetic tunnel junction structure comprising:
 a first amorphous ferromagnetic material layer formed on a substrate;   a tunnel barrier layer on said first amorphous ferromagnetic material layer; and   a second ferromagnetic material layer formed on said tunnel barrier layer, wherein   said tunnel barrier layer comprises a poly-crystalline MgO in which ( 001 ) crystal plane is preferentially oriented, and said MgO has oxygen vacancy defects.   
     
     
         16 . The magnetoresistive device according to  claim 15 , wherein said first and second amorphous ferromagnetic material layers comprise CoFeB alloy. 
     
     
         17 . A magnetoresistive device having a magnetic tunnel junction structure comprising:
 a tunnel barrier layer deposited on an amorphous ferromagnetic material layer, wherein   said tunnel barrier layer comprises a poly-crystalline MgO in which ( 001 ) crystal plane is preferentially oriented, and said MgO has oxygen vacancy defects.   
     
     
         18 . The magnetoresistive device according to  claim 17 , wherein said first and second amorphous ferromagnetic material layers comprise CoFeB alloy. 
     
     
         19 . A magnetic multilayer film comprising:
 a first amorphous ferromagnetic material layer formed on a substrate;   a tunnel barrier layer deposited on said first amorphous ferromagnetic material layer; and   a second ferromagnetic material layer deposited on said tunnel barrier layer, wherein   said tunnel barrier layer comprises a poly-crystalline magnesium oxide in which ( 001 ) crystal plane is preferentially oriented.   
     
     
         20 . The magnetoresistive device according to  claim 19 , wherein said first amorphous ferromagnetic material layer comprises CoFeB alloy.