Magnetic Properties and Writing Characteristics of Magnetic Clad Lines in Magnetoresistive Random Access Memory Devices

Structural and magnetic properties of magnetic clad lines used for magnetoresistive random access memory (MRAM) devices were analyzed to optimize the clad-line fabrication process. Patterns of 520 nm lines and 280 nm spaces with a depth of 300 nm with magnetic cladding films of Ta/NiFe/Ta were fabricated to characterize the structure and magnetic properties of cladding films by transmission electron microscopy and magnetic measurements. A high susceptibility with a small hysteresis was obtained when a NiFe cladding film highly oriented to fcc (111) was formed perpendicular to the sidewall depth direction. The optimized cladding film was integrated in MRAM cells and we confirmed that the clad lines reduced the flop current of a toggle-MRAM cell by more than 50% compared with a cell having unclad lines. The flop cur-rent distribution can be reduced by applying a magnetic field of 12 kOe in the direction of word lines at room temperature. We successfully confirmed writing operation in a 4-Mbit MRAM cell with these optimized magnetic clad lines. [DOI: 10.1143/JJAP.47.3456]