Annealing stability study of Co₂₀Fe₆₀B₂₀\MgO\Co₂₀Fe₆₀B₂₀perpendicular magnetic tunnel junctions

Abstract

A full Co20Fe60B20\MgO\ Co20Fe60B20 perpendicular magnetic tunnel junction (pMTJ) with (Co\Pt) multilayers as pinning layers and different functional multilayers stacks were made and annealed at different temperatures. The tunneling magnetoresistance ratio (TMR) and MgO barrier resistance-area product (RA) were measured and analyzed as a function of annealing temperature. The TMR of pMTJs dramatically declines with increasing annealing temperatures from 320 °C to 400 °C while the RA increases with temperature from 375 °C to 450 °C. The pMTJs and partial stacks were also measured in a vibrating sample magnetometer (VSM). We found that the (Co\Pt) multilayers are very stable and maintain a magnetization direction perpendicular to the film plane up to 450 °C. However, the magnetization direction of the CoFeB above and below the MgO barrier rotates from perpendicular to in-plane with increasing annealing temperature. Furthermore, the CoFeB layer influences the adjacent (Co\Pt) layers to rotate at the same time. The pMTJs’ elemental depth profiles in the as deposited and annealed states were determined by Secondary Ion Mass Spectrometry (SIMS). We found that Boron and Tantalum migrate towards the top of the stack. The other elements (Platinum, Cobalt, Ruthenium, and Magnesium) are very stable and do not interdiffuse during annealing up to 450°C.

Device Modeling of MgO-Barrier Tunneling Magnetoresistors for Hybrid Spintronic-CMOS

“…The temperature dependence of TMR in MTJs is presented in [28,29]. Although there exist the influences of different deposition procedures and annealing temperatures on the TMR sensor response [30], the simulation results become a reliable reference in the fabrication of certain material combinations and sensor shapes and enhance the interest of the use of a finite element software for the prediction of a model.…”

FORC+ analysis of perpendicular magnetic tunnel junctions

“…2. 13 The sample was deposited onto a 20 cm diameter thermally oxidized wafer using a Singulus TIMARIS sputtering system 14 with a base pressure less than 8 x 10 -7 Pa (6 x 10 -9 Torr).…”

Nonmonotonic aftereffect measurements in perpendicular synthetic ferrimagnets

“…Perpendicularly magnetized synthetic ferrimagnets made of two antiferromagnetically exchange-coupled magnetic layers are very attractive materials for spintronic devices, and have gathered a great deal of attention in the past decades. Numerous materials, such as [Pt/Co]Ru[Co/Pt] [1], CoFeB/(Ta or MgO)/CoFeB [2][3][4], [Co/Pd]Ru[Co/Pd] [4], or even Heusler alloys [5] or graphene [6] are suitable for the growth of these multilayers that consist of two ferromagnetic layers separated by a nonmagnetic spacer providing an antiferromagnetic coupling between them. Since there are plenty of useful applications to these magnetic structures, various studies explore in details the properties of these materials that are nowadays routinely used in magnetic memory devices, mainly as pinned layers in perpendicular magnetic tunnel junctions [7][8][9].…”