System and method for processing a wafer including stop-on-alumina processing

Abstract

Magnetic tunnel junction (MTJ) devices can be fabricated by a stop-on-alumina process whereby the tunnel junction layer serves as the stop layer during plasma overetching of the upper magnetic layer. The resulting side walls of the MTJ device are non-vertical in the vicinity of the tunnel junction layer which serves to electrically isolate the upper magnetic layer from the lower magnetic layer. The gas employed during plasma overetching excludes halogen containing species which results in highly selective etching of the magnetic layer vis-à-vis the alumina tunnel barrier layer. The introduction of oxygen in the gas may enhance the reproducibility of the overetch process. Finally, plasma treatment with He and H 2 followed by rinsing and baking subsequent to removal of the photoresist mask during the fabrication process enhances yield.

1 . A magnetic tunnel junction device comprising: 
 (a) a first or lower magnetic member;    (b) a second or upper magnetic member; and    (c) an insulating tunnel barrier layer that comprises a dielectric material located between the first magnetic member and the second magnetic member wherein at least one side portion of the second magnetic member and of the insulating tunnel barrier layer define a non-vertical profile which protrudes from the at least one side portion.    
   
   
       2 . The magnetic tunnel junction device of  claim 1  wherein the dielectric material comprises Al 2 O 3 .  
   
   
       3 . The magnetic tunnel junction device of  claim 1  wherein the first magnetic member is a fixed ferromagnetic layer having a magnetic moment that is fixed in a preferred direction in the presence of an applied magnetic field in a specified range and the second magnetic member is a free ferromagnetic layer whose magnetic moment is free to rotate in the presence of an applied magnetic field in the specified range  
   
   
       4 . The magnetic tunnel junction device of  claim 3  wherein the fixed and free ferromagnetic layers are formed from a material that is selected from the group consisting of NiFe, CoFe, CoFeB, NiFeCr, CoNiFe and mixtures thereof.  
   
   
       5 . The magnetic tunnel junction device of  claim 1  further comprising: 
 (d) a support substrate;    (e) a first conductive non-magnetic contact layer that is formed on the support substrate; and    (f) a second conductive non-magnetic contact layer that is formed on an upper surface of the second magnetic member.    
   
   
       6 . The magnetic tunnel junction device of  claim 5  wherein the first and second conductive non-magnetic contact layers are formed from material that is selected from the group consisting of Ta, Ti and mixtures thereof.  
   
   
       7 . The magnetic tunnel junction device of  claim 1  wherein the insulating tunnel barrier layer defines a width that is greater than that of the second magnetic member.  
   
   
       8 . The magnetic tunnel junction device of  claim 1  wherein the second magnetic member has a width W 2 , the first magnetic member has a width W 1 , the insulating tunnel barrier layer which has a width W 3 , wherein W 1 ≧W 3 >W 2 .  
   
   
       9 . The magnetic tunnel junction device of  claim 1  wherein an outer perimeter of the device includes at least part of the second magnetic member and of the insulating tunnel baffler layer define a non-vertical profile, and the second magnetic member has a width that is less than that of the tunnel barrier layer.  
   
   
       10 . The magnetic tunnel junction device of  claim 1  wherein an outer perimeter of the device includes at least part of the first magnetic member and of the insulating tunnel barrier layer define a non-vertical profile, and the second magnetic member has a width that is less than that of the tunnel barrier layer.  
   
   
       11 . A magnetic tunnel junction device comprising: 
 (a) a first or lower magnetic member;    (b) a second or upper magnetic member; and    (c) an insulating tunnel barrier layer that comprises a dielectric material located between the first magnetic member and the second magnetic member wherein at least one side portion of the first magnetic member and of the insulating tunnel barrier layer define a non-vertical profile which protrudes from the at least one side portion.    
   
   
       12 . The magnetic tunnel junction device of  claim 11  wherein the insulating tunnel barrier layer defines a width that is greater than that of the second magnetic member.  
   
   
       13 . The magnetic tunnel junction device of  claim 11  wherein the second magnetic member has a width W 2 , the first magnetic member has a width W 1 , the insulating tunnel barrier layer which has a width W 3 , wherein W 1 ≧W 3 >W 2 .  
   
   
       14 . The magnetic tunnel junction device of  claim 11  wherein an outer perimeter of the device includes at least part of the second magnetic member and of the insulating tunnel baffler layer define a non-vertical profile, and the second magnetic member has a width that is less than that of the tunnel barrier layer.  
   
   
       15 . The magnetic tunnel junction device of  claim 11  wherein an outer perimeter of the device includes at least part of the first magnetic member and of the insulating tunnel barrier layer define a non-vertical profile, and the second magnetic member has a width that is less than that of the tunnel barrier layer.  
   
   
       16 . A magnetic tunnel junction device comprising: 
 (a) a first or lower magnetic member;    (b) a second or upper magnetic member; and    (c) an insulating tunnel barrier layer that comprises a dielectric material electrically separating the second magnetic member which has an outer perimeter positioned on an upper surface of the insulating tunnel barrier layer and the first magnetic member which is underneath the insulating tunnel barrier layer.    
   
   
       17 . The magnetic tunnel junction device of  claim 16  wherein the insulating tunnel barrier layer defines a width that is greater than that of the second magnetic member.  
   
   
       18 . The magnetic tunnel junction device of  claim 16  wherein the second magnetic member has a width W 2 , the first magnetic member has a width W 1 , the insulating tunnel barrier layer which has a width W 3 , wherein W 1 ≧W 3 >W 2 .  
   
   
       19 . The magnetic tunnel junction device of  claim 16  wherein an outer perimeter of the device includes at least part of the second magnetic member and of the insulating tunnel baffler layer define a non-vertical profile, and the second magnetic member has a width that is less than that of the tunnel barrier layer.  
   
   
       20 . The magnetic tunnel junction device of  claim 16  wherein an outer perimeter of the device includes at least part of the first magnetic member and of the insulating tunnel barrier layer define a non-vertical profile, and the second magnetic member has a width that is less than that of the tunnel barrier layer.