Importance of SAF Stability against Temperature and Magnetic Field in Automotive-Grade-1 STT-MRAM Wafer Electrical Testing

We investigate the automotive grade 1 temperature response of different MTJ stack designs based on the state-of-the-art GlobalFoundries 22FDX® Embedded-MRAM technology. An anomalous reference system reversal occurred in some devices as a response to external magnetic fields at operating temperatures as high as 150 °C. The strength of the external magnetic field, temperature and degree of magnetic moment mismatch of the synthetic antiferromagnet (SAF) reference system all affect the severity of the reference system’s instability. By careful stack optimization of the SAF reference system, the anomalous reversal was successfully suppressed in the investigated external magnetic field and temperature regime.