Thermal Assisted Switching

Thermal Assisted Switching, or TAS, is one of the new 2nd generation approaches to MRAM currently being developed. A few different designs have been proposed, but all rely on the idea of reducing the required switching fields by heating[1]. The first design’s cell, which was proposed by Daughton and co-workers, had a heating element, an MRAM bit, an orthogonal digit line[1], and used a low Curie point ferromagnetic material as the storage layer[2]. In a second and more promising design, which was developed by the Spintec Laboratory (France) and subsequently licensed to Crocus Technology, the storage layer is made of a ferromagnetic and an antiferromagnetic layer. When the cell is heated by flowing a heating current through the junction and the temperature exceeds the “blocking temperature” (Tb), the ferromagnetic layer is freed and the data is written by application of a magnetic field while cooling down[1]. When idle, the cell’s temperature is below the blocking temperature and much more stable[3].

This approach offers multiple advantages over previous MRAM technologies[2]:

(a) Because the write selection is temperature driven, it eliminates write selectivity problems,
(b) It is a low-power approach as only one magnetic field is required to write and because the cell stability and magnetic susceptibility are decoupled as a result of the introduction of the blocking temperature,
(c) It is thermally stable due to the exchange bias of the storage layer.

References

  1. ^ a b c Non-volatile Magnetic Random Access Memories http://www.crocus-technology.com/pdf/MRAM_CR_v5a.pdf
  2. ^ a b Thermally Assisted MRAM http://crocustechnology.com/pdf/Prejbeanu_JPCM_special_issue_revised.pdf
  3. ^ The Emergence of Practical MRAM http://crocustechnology.com/pdf/BH_GSA_Article.pdf