Ultrafast flash lamp annealing of magnetic tunnel junctions

Thermal annealing is often the rate-limiting step in device fabrication. In magnetic tunnel junctions (MTJs), which are key components of nonvolatile magnetic random access memories and ultra-sensitive magnetic field sensors, high-temperature annealing is required to achieve a high tunnel magnetoresistance (TMR) ratio. Conventional thermal annealing (CTA) in a furnace typically takes several hours, including heating and cooling. Here, we show that flash lamp annealing (FLA) can drastically shorten the process time for MTJs compared with CTA. In FLA, a sequence of millisecond-scale Xe-lamp pulses is directed onto the device surface, rapidly heating it to high temperature and enabling the MTJ to reach a TMR ratio of ~100% within two seconds, completing the annealing process. Additionally, we observed differences in atomic diffusion and ferromagnetic layer crystallization between MTJs subjected to FLA and those subjected to CTA, as revealed by structural and compositional analyses.