P-STT-MRAM thermal stability and modeling of its temperature dependence

Due to their high speed[1], high endurance[2] and non-volatility, perpendicular STT-MRAM (P-STT-MRAM) are seen as one of the best candidate for non volatile memory embedded applications. However, their data retention time at elevated temperature such as the soldering reflow criterion and the automotive application temperature range is still a critical point. In this paper, P-STT-MRAM devices with diameters ranging from 20nm to 150nm have been tested in temperature. The thermal stability factor has been extracted electrically for temperatures up to 190°C. Then the loss in the Curie temperature of the storage layer compared to bulk values has been measured and directly linked to the thermal stability values. At last, a model is proposed to predict the temperature dependance of the thermal stability factor.