Research On The Fabrication Of Magnetic Tunnel Junction Nano-cells Based On Focused Ion Beam

Spin Torque Transfer Magnetic Random Access Memory(STT-MRAM), is a new non-volatile memory. STT-MRAM has many advantages, like high integration, low power consumption, high read/write speed. Magnetic tunnel junction(MTJ) is a key part of STT-MRAM memory cells. Based on current technologies, there are many ways to fabricate nano-MTJ cells, but they all have the disadvantages of complicated steps and high cost. This paper proposes a new method to fabricate MTJ nano cells. The method does not involve electron-beam lithography and wet etching process. It is mainly based on Focused Ion beam technology(FIB) and traditional lithography. This process eliminates one of the lithographic steps, and has better control on feature size, at the mean time it saves both cost and time.Firstly, effective area of nano-MTJ model based on ANSYS was calculated, proving this structure is feasible. Then, the TMR theoretical value with applied electric field was calculated through the micro-magnetic simulation. Finally, the sample was prepared based on FIB technology, and the physical and electrical performance of nano-MTJ cells was tested. The cell shape of the structure was good and clear. The measured TMR value with applied electric field was 27.56%, which confirmed the structure based on FIB technology was feasible in experiment, and it can be used to realize MTJ nano contact. Besides, a seperate-crossbar structure was designed to eliminate the crosstalk between the units and the possibility of series¶llel connection, increasing the accuracy of the experimental testing.This preparation process based on FIB technology completed the fabrication of MRAM memory cells which has been proved to have the effect of STT, provides a certain amount of experimental evidence for the preparation and performance study of nano-MTJ cells in the future.