| MgO based magnetic tunnel junctions（MTJs）are the application hotspots in the field of spintronics and promote the development of spintronic devices.However,there is still a gap between the theoretical and experimental values of MgO magnetic tunnel junctions,and its tunneling magnetoresistance effect（TMR）remains to be studied.In this paper,the working mechanism of magnetic tunnel junctions is given,the effects of element diffusion oxidation and interface structure on tunneling magnetoresistance effect in MgO magnetic tunnel junctions are theoretically analyzed,and the preparation conditions and surface morphology of buffer layer,free layer and barrier layer of magnetic tunnel junctions are studied.In order to improve the TMR ratio of MgO magnetic tunnel junctions,two types of sandwich MgO magnetic tunnel junctions are studied.One is EB-SV type,which uses Ir Mn as the pinning layer to fix the magnetization direction of a ferromagnetic layer;The other is PSV type.The tunnel junctions cancels the pinning layer,modulates the coercivity through the ferromagnetic layer thickness,and uses Pt metal intercalation to improve the interface structure of MgO magnetic tunnel junctions to improve the TMR ratio.On this basis,the preparation conditions and magnetic annealing process of MgO magnetic tunnel junctions are optimized.The 4-inch wafer of MgO magnetic tunnel junctions is fabricated by microelectronic processing technology,and non magnetized packaging and test analysis are carried out.At room temperature,the I-V characteristics and magnetoresistance characteristics of two types of MgO magnetic tunnel junctions are studied by using semiconductor parameter tester and high and low temperature Hall effect test system.The results show that MgO magnetic tunnel junctions has a certain tunneling magnetoresistance effect,and the TMR ratio of EB-SV MgO magnetic tunnel junctions is about 20%;Compared with the traditional EB-SV MgO magnetic tunnel junctions,the TMR ratio of PSV MgO magnetic tunnel junctions is about 62%;The tunneling magnetoresistance effect of PSV MgO magnetic tunnel junctions with Pt insertion layer is more significant,and the TMR ratio is about 91%.The results show that canceling the pinning layer Ir Mn and adding Pt intercalation can improve the tunneling magnetoresistance effect of CoFeB/MgO/CoFeB magnetic tunnel junctions,increase the TMR ratio,and lay a foundation for the research of MgO magnetic tunnel junctions. |
