Process flow of Everspin MRAM memory chip

As a high-performance nonvolatile memory device,Everspin MRAM memory chip is widely used in various industrial and high-end electronic scenes with its advantages of high reliability and low power consumption.The preparation of MRAM memory chip mainly depends on the back-end process of semiconductor wafer factory,and the precision of the whole process is demanding.
 

The preparation of bottom electrode is the basic process of Everspin MRAM memory chip production.The industry uses mature patterning and mosaic technology to build the electrode bottom layer.After the preparation,the surface layer needs to be precisely polished to build an ultra-smooth and flat substrate surface,which provides qualified process conditions for the subsequent deposition of MTJ stack.In production,it is necessary to strictly control the flatness and height dimensions of electrodes,avoid process defects in the whole process,and ensure the deposition accuracy of subsequent multi-layer structures.
 

MTJ stack deposition is the core process of MRAM memory chip manufacturing.Everspin adopts integrated PVD physical vapor deposition equipment,which accurately stacks 20 to 30 layers of metal and insulating films,and the thickness of a single layer is controlled at 0.2-5.0nm.The deposition accuracy of the core MgO-MgO tunneling barrier layer can reach 0.01nm,which directly affects the two core parameters of RA resistance area product and TMR tunneling magnetoresistance,and slight process deviation will cause chip performance degradation.
 

Magnetic annealing process is used to shape the crystal structure and magnetic properties of MTJ stack.After the deposition,the wafer needs to be annealed in a magnetic field and high temperature environment to optimize the interface material and fix the magnetization direction.After the process,the staff will comprehensively test the electrical and magnetic properties of the chip and control the process stability through online measurement.
 

MTJ column patterning and top electrode preparation are the key working procedures.The process needs to accurately carve the 20-100nm miniature circular storage column structure,and through precision lithography and ion beam etching technology,the problems such as metal deposition on the side wall and layer damage can be avoided,and the column size and shape can be strictly controlled.Finally,the top electrode is formed by double damascene process,and the MTJ core structure is fully protected by defect-free packaging layer to ensure the stable mass production of Everspin MRAM memory chips.