Application and Improvement of Precise Resistance Tracing Technique for a Toggle Mode MRAM Evaluation

A precise evaluation technique was created for developing magnetoresistive random access memory (MRAM), especially memory that operates in a toggle-writing mode. This technique enables us to observe the detailed resistance transition of magnetic tunneling junction (MTJ) cells during complicated write operations. It was used to analyze incomplete operation and failed cells, and revealed that the MTJ characteristics in the third quadrant are significantly related to disturb robustness in megabit MRAM. To improve sensitivity to failed cells, we prepared 16-kbit MRAM test structures with a high-speed failed-cell check mode. We found our technique to be a powerful method of failure analysis and expect it to accelerate MRAM development.