The current technology of non-volatile memories is dominated by Flash memories which are used in numerous large-scale consumer applications (for example in digital cameras, USB sticks, etc). They are rewritable, semi-conductor memories.
The technological development of these Flash memories however is facing a certain number of obstacles. Their service life is limited, their writing and erasure times are relatively great (over 10 μs and 1 ms respectively) and they require high voltages (over 10 V) in order to store data. Besides, this technology is reaching its limits in terms of size reduction.
Recently, RRAMs and MEMRISTORs have appeared as alternative solutions to Flash memories. Indeed, in RRAMs and MEMRISTORs, very short electrical pulses, generally of the order of 100 ns, generate a variation in the electrical resistance of a simple device constituted by two electrodes separated by an active material.
The term “active material” is understood here below in the description to mean a material capable of taking at least two distinct states of electrical resistance through the application of electrical pulses.
There are different types of active materials known in the prior art. These active materials, which are incorporated into RRAMs or MEMRISTORs, are for example: NiO, TiO2, SrTiO3.
Now, at present, these memories still undergoing experimentation as the underlying physical/chemical phenomena are as yet poorly understood and therefore poorly mastered. The industrial-scale application of such memories therefore raises real difficulties. Indeed, these memories do not entirely meet the requirements fixed by the ITRS (International Technology Roadmap for Semiconductors), especially in the matter of switching voltage, temperature, memory window, service life and integration.