High write selectivity and low power magnetic random access memory and method for fabricating the same

Abstract

A low-power magnetic random access memory (MRAM) with high write selectivity is provided. Write word lines and pillar write word lines covered with a magnetic material are disposed in an zigzag relation, solving the magnetic interference problem generated by cells adjacent to the pillar write word line in the magnetic RAM with the pillar write word line form. According to the disclosed structure, each of the cells has a smaller bit size and a lower write current. This effectively reduces the power consumption of the MRAM.

1 . A magnetic random access memory (MRAM) with high write selectivity and low power consumption, comprising: 
 a plurality of magnetic memory cells, each of the magnetic memory cells having a magnetic tunnel junction cell and a lower electrode, the memory state of the magnetic memory cells being determined by the magnetization orientation of the magnetic tunnel junction cell;    a plurality of bit lines, each of the bit lines providing a channel for the read and write currents of the corresponding magnetic memory cell;    a plurality of middle metal pillars, each of the middle metal pillars connecting to the corresponding magnetic memory cell and the corresponding bit line;    a plurality of write word lines, each of the write word lines having an upper layer write word line and a lower layer write word line; and    a plurality of pillar write word lines, each of the pillar write word lines connecting the associated upper layer write word line and lower layer write word line for providing a write current channel for the corresponding magnetic memory cell, thereby enhancing the induced magnetic field at the corresponding magnetic memory cell, wherein the pillar write word lines of the adjacent magnetic memory cells are disposed in an zigzag relation.    
   
   
       2 . The MRAM of  claim 1 , wherein the pillar write word lines is covered with a sidewall keeper except for the part facing the magnetic tunnel junction cell.  
   
   
       3 . The MRAM of  claim 2 , wherein the sidewall keeper is made of a magnetic material with high permeability.  
   
   
       4 . The MRAM of  claim 3 , wherein the magnetic material is one selected from the group consisting of the permalloy and the Ferri magnet.  
   
   
       5 . A method for making a magnetic random access memory (MRAM) with high write selectivity and low power consumption, after forming the MTJ cell of the MRAM, the method further comprising steps of: 
 forming two pillar write word lines on both sides of the magnetic memory cell and a middle metal pillar;    forming a sidewall keeper on the pillar write word line except for the part facing the magnetic memory cell; and    forming a bit line of the MRAM.    
   
   
       6 . The method of  claim 5 , wherein the sidewall keeper is made of magnetic material with high permeability.  
   
   
       7 . The method of  claim 6 , wherein the magnetic material is one selected from the group consisting of the permalloy and the Ferri magnet.  
   
   
       8 . The method of  claim 5 , wherein the step of forming the middle metal pillar and the pillar write word lines is accomplished using the processes of lithography alignment, etching, filling, and chemical mechanical polishing (CMP) sequentially.  
   
   
       9 . The method of  claim 5 , wherein the step of forming the sidewall keeper is accomplished using the processes of lithography alignments etching, filling a magnetic material, and etching back sequentially.  
   
   
       10 . A magnetic random access memory (MRAM) comprising: 
 a plurality of magnetic memory cells, each of the magnetic memory cells having a magnetic tunnel junction cell and a lower electrode and whose memory state is determined by changing its magnetization orientation;    a plurality of bit lines, each of the bit lines providing a read/write current channel for a corresponding magnetic memory cell;    a plurality of middle metal pillars, each of the middle metal pillars connecting the associated magnetic memory cell and bit line;    a plurality of write word lines, having an upper layer write word line and a lower layer write word line; and    a plurality of pillar write word lines, each of the pillar write word lines connecting the upper layer write word line and the lower layer write word line for providing the write current channel for the magnetic memory cell, thereby enhancing the induced magnetic field at the magnetic memory cell, the pillar write word lines of the adjacent memory units disposed in an zigzag relation.    
   
   
       11 . The MRAM of  claim 10 , wherein each of the pillar write word lines is covered by a sidewall keeper except for the part facing the magnetic tunnel junction cell.  
   
   
       12 . The MRAM of  claim 11 , wherein the sidewall keeper is made of magnetic material with high permeability.  
   
   
       13 . The MRAM of  claim 12 , wherein the magnetic material is one selected from the group consisting of the permalloy and the Ferri magnet.  
   
   
       14 . The MRAM of  claim 1 , wherein each of the pillar write word lines extends in a vertical direction, an upper end of each of the pillar write word lines being inn contact with a corresponding upper layer write word line, a lower end of each of the pillar write word lines being in contact with a corresponding lower layer write word line, the upper layer write word line and the lower layer write word line being perpendicular to the corresponding pillar write word line.  
   
   
       15 . The MRAM of  claim 2 , wherein the side wall keeper confines magnetic flux on the magnetic tunnel junction cell so that the adjacent magnetic tunnel junction cells are not affected by the magnetic field produced by the pillar write word line.  
   
   
       16 . The MRAM of  claim 2 , wherein the side wall keeper is in contact with the corresponding pillar write word.  
   
   
       17 . The MRAM of  claim 10 , wherein each of the pillar write word lines extends in a vertical direction, an upper end of each of the pillar write word lines being inn contact with a corresponding upper layer write word line, a lower end of each of the pillar write word lines being in contact with a corresponding lower layer write word line, the upper layer write word line and the lower layer write word line being perpendicular to the corresponding pillar write word line.  
   
   
       18 . The MRAM of  claim 11 , wherein the side wall keeper confines magnetic flux on the magnetic tunnel junction cell so that the adjacent magnetic tunnel junction cells are not affected by the magnetic field produced by the pillar write word line.  
   
   
       19 . The MRAM of  claim 11 , wherein the side wall keeper is in contact with the corresponding pillar write word.