Evaluation of a new MgO barrier based on CoFeB/MgO/CoFeB structure for advanced MRAM applications

Abstract

MRAM technology offers the opportunity to provide all the advantages of the most popular types of memory, such as DRAM, SRAM and FLASH with none of its disadvantages. Magnetic tunnel junctions (MTJs) based on CoFeB/MgO/CoFeB structures are very promising for future spintronics, especially in MRAM memory operation due to its high tunnel magnetoresistance (TMR) and reasonable range of resistance area product (RA). The deposition process of MgO barrier in such structures is one of the most difficult challenges to achieve good parameters of MTJs and it strongly affects on the barrier roughness, especially on the low RA region because of insufficient crystallization of thin MgO on an amorphous CoFeB. Ordinary MgO barrier creation takes a long time due to obligatory steps of Mg oxidation in different module that makes process complicated and provides a risk of CoFeB oxidation through Mg. It is shown that the new approach of barrier formation using in-situ MgO RF sputtering with Mg insertions and higher Ar partial pressure has very promising ratio of TMR vs RA which can be used in MTJs required for low “read” and “write” currents having a big delta between Rmin and Rmax in the most advanced MRAM applications.