In the selection of nonvolatile memory,MRAM(Magnetic Random Access Memory)and FRAM(Ferroelectric Random Access Memory)are often compared side by side.Both of them support byte-level writing and power-off storage,and do not need to be erased before writing,but the storage mechanism is different,so the durability and temperature adaptability are divided.
First,the storage mechanism
MRAM adopts 1T-1MTJ structure,and represents"1"and"0"with the relative orientation of the magnetic moments of the free layer and the fixed layer in the magnetic tunnel junction,and measures the change of tunneling magnetoresistance when reading.Magnetic moment reversal only changes the spin direction and does not involve atomic migration.FRAM is 1T-1FC structure,and records data by the polarization direction formed by the displacement of Ti⁴⁺ions in ferroelectric thin films(mostly PZT)in the oxygen octahedron.The writing essence is the ion displacement driven by an electric field.
Second,durability
There is no displacement of atoms or electrons in the writing process of MRAM,so there is no intrinsic wear mechanism and the access life can reach 10 times.Repeated flipping of the dipole of FRAM will lead to fatigue,free charge and ion defects will gradually accumulate,and due to the bonding between the ferroelectric dipole and hydrogen,the number of writeable times is usually more than one order of magnitude lower.
Third,data retention
There is inherent asymmetry in the hysteresis behavior of FRAM:the bottom electrode bears a higher thermal budget than the top electrode,forming a preferred orientation,and it is difficult for the programming voltage to pull the dipole out of this orientation after long-term use,and the memory cell may be locked.In the read operation,the voltage is divided between the parasitic capacitor and the ferroelectric capacitor,and the signal margin decreases with the number of accesses.When the ambient temperature exceeds 85℃,the accumulation of free charge accelerates and branding appears.MRAM has been verified for 20 years at 125℃.
Fourth,Selection Reference
High-frequency writing,wide temperature and long-life recording scenarios,such as power monitoring,vehicle-mounted black box and industrial data recording,are more suitable for MRAM；;FRAM still has cost and ecological advantages in low power consumption and medium writing frequency measuring instruments.The actual selection should take writing frequency,working temperature and life requirement as the primary constraints.For further information about product data or sample application,please contact RAMUSN for professional services.
Keywords：MRAM
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