Magnetoresistive element

Abstract

According to one embodiment, a magnetoresistive element comprises a storage layer as a ferromagnetic layer which has magnetic anisotropy perpendicular to film planes, and in which a magnetization direction is variable, a reference layer as a ferromagnetic layer which has magnetic anisotropy perpendicular to film planes, and in which a magnetization direction is invariable, a tunnel barrier layer as a nonmagnetic layer formed between the storage layer and the reference layer, and a first underlayer formed on a side of the storage layer, which is opposite to a side facing the tunnel barrier layer, and containing amorphous W.

What is claimed is: 
     
         1 . A magnetoresistive element comprising:
 a storage layer as a ferromagnetic layer which has magnetic anisotropy perpendicular to film planes, and in which a magnetization direction is variable;   a reference layer as a ferromagnetic layer which has magnetic anisotropy perpendicular to film planes, and in which a magnetization direction is invariable;   a tunnel barrier layer as a nonmagnetic layer formed between the storage layer and the reference layer; and   a first underlayer formed on a side of the storage layer, which is opposite to a side facing the tunnel barrier layer, and containing amorphous W.   
     
     
         2 . The element of  claim 1 , further comprising a second underlayer formed on a side of the first underlayer, which is opposite to a side facing the storage layer, and containing an amorphous conductive material. 
     
     
         3 . The element of  claim 2 , wherein the conductive material is a metal to which a metalloid is added. 
     
     
         4 . The element of  claim 2 , wherein the conductive material is CoFeB. 
     
     
         5 . The element of  claim 2 , wherein the second underlayer contains W. 
     
     
         6 . The element of  claim 2 , wherein the second underlayer is a ferromagnetic layer which has magnetic anisotropy perpendicular to film planes, and in which a magnetization direction is variable. 
     
     
         7 . The element of  claim 2 , wherein a thickness of the first underlayer is 8 Å or more to 20 Å or less, and a thickness of the second underlayer is 1 Å or more to 20 Å or less. 
     
     
         8 . The element of  claim 2 , wherein a thickness of the first underlayer is 1 Å or more to 3 Å or less, and a thickness of the second underlayer is 3 Å or more to 15 Å or less. 
     
     
         9 . The element of  claim 1 , wherein a thickness of the first underlayer is not more than 20 Å. 
     
     
         10 . The element of  claim 2 , wherein the second underlayer further contains a crystalline conductive material. 
     
     
         11 . The element of  claim 1 , wherein the storage layer contains crystalline CoFeB. 
     
     
         12 . The element of  claim 1 , wherein a thickness of the storage layer is 8 Å or more to 15 Å or less. 
     
     
         13 . The element of  claim 2 , further comprising a buffer layer formed on a side of the second underlayer, which is opposite to a side facing the first underlayer, and containing one of W, Mo, and Ta. 
     
     
         14 . A magnetoresistive element manufacturing method comprising:
 forming a first underlayer containing amorphous W;   forming, on the first underlayer, a storage layer as a ferromagnetic layer which has magnetic anisotropy perpendicular to film planes, and in which a magnetization direction is variable;   forming a tunnel barrier layer as a nonmagnetic layer on the storage layer; and   forming, on the tunnel barrier layer, a reference layer as a ferromagnetic layer which has magnetic anisotropy perpendicular to film planes, and in which a magnetization direction is invariable.   
     
     
         15 . The method of  claim 14 , further comprising forming a second underlayer containing an amorphous conductive material, before the forming the first underlayer,
 wherein the first underlayer is formed on the second underlayer.   
     
     
         16 . The method of  claim 14 , wherein the first underlayer is formed by sputtering, and has a thickness of not more than 20 Å. 
     
     
         17 . The method of  claim 14 , wherein the second underlayer, the first underlayer, the storage layer, and the reference layer are formed by sputtering in a first chamber, and the tunnel barrier layer is formed by sputtering in a second chamber different from the first chamber. 
     
     
         18 . The method of  claim 14 , further comprising performing annealing after the forming the reference layer, wherein the first underlayer contains amorphous W after the annealing. 
     
     
         19 . The method of  claim 18 , wherein the second underlayer partially crystallizes in the annealing. 
     
     
         20 . A magnetoresistive element manufacturing method comprising:
 forming a reference layer as a ferromagnetic layer which has magnetic anisotropy perpendicular to film planes, and in which a magnetization direction is invariable;   forming a tunnel barrier layer as a nonmagnetic layer on the reference layer;   forming, on the tunnel barrier layer, a storage layer as a ferromagnetic layer which has magnetic anisotropy perpendicular to film planes and contains amorphous CoFeB, and in which a magnetization direction is variable; and   forming a first underlayer containing amorphous W on the storage layer.