There is a frequent demand for smaller devices with more memory. Some efforts have been initiated in resistive memory as a mechanism for creating more memory in less space. Resistive memory systems use a resistive element that can change and maintain the value of its resistivity based on applied electrical conditions. Resistive memory systems use a resistive element that can change and maintain the value of its resistivity based on applied conditions. An example of such a resistive switching device is a metal-insulator-metal device.
A metal-insulator-metal device can be set to a low resistive state when certain electrical conditions form a current path through the insulator material. Alternatively, the device can be set to a high resistive state when this certain applied electrical conditions break this path. Of practical importance, a metal-insulator-metal device can be used to represent logical values. For example, a high resistive state may be used to represent a logical ‘1’ while a low resistive state may be used to represent a logical ‘0’.
Resistive memory systems are often constructed as an array of resistive memory cells, with each cell being placed on intersecting conductive lines. Typically, such an array is formed in several layers. There is a layer for the bottom conductive lines, a layer for the bottom electrodes of the resistive memory cell, a layer for the insulator portion of the resistive switching device, a layer for the top electrode of the resistive switching device, and a layer for the top intersecting conductive lines. Each of these layers is specifically formed through standard photolithographic patterning processes. It is desirable, however, to be able to fabricate such memory arrays in as few steps as possible.