As memory continues to scale further and densities continue to increase, leakage current becomes a non-trivial concern. A selector device limits the leakage current from memory elements so that the current passing through a selected device significantly exceeds the residual leakage. An MIM device can be used in conjunction with a memory element to invoke non-linear I-V characteristics. A Ni/TiO2/Ni film stack was chosen for three main reasons: a large non-linearity factor, high on/off current ratio, and bipolar switching capabilities. An on/off ratio of six orders of magnitude was observed, and current densities on the order of 10kA/cm2 were realized using devices with one-half micron feature sizes. It was shown that current density does not scale with device size, but instead increases with decreasing device area. This confirms that required current densities are realistically achievable with continued scaling.
"Investigation of MIM Structures as Selector Devices for Crossbar Memory Arrays,"
Journal of the Microelectronic Engineering Conference: Vol. 22
, Article 22.
Available at: http://scholarworks.rit.edu/ritamec/vol22/iss1/22