Ovonic Unified Memory
Nowadays, digital memories are used in each and every fields of day-to-day life. Semiconductors form the fundamental building blocks of the modern electronic world providing the brainsand the memory of products all around us from washing machines to super computers. But now we are entering an era of material limited scaling. Continuous scaling has required the introduction of new materials. Current memory technologies have a lot of limitations. The new memory technologies have got all the good attributes for an ideal memory. Among them Ovonic Unified Memory (OUM) is the most promising one. OUM is a type of nonvolatile memory, which uses chalcogenide materials for storage of binary data. The term “chalcogen” refers to the Group VI elements of the periodic table.“Chalcogenide” refers to alloys containing at least one of these elements such as the alloy of germanium, antimony, and tellurium, which is used as the storage element in OUM. Electrical energy (heat) is used to convert the material between crystalline (conductive) and amorphous (resistive) phases and the resistive property of these phases is used to represent 0s and 1s. To write data into the cell, the chalcogenide is heated past its melting point and then rapidly cooled to make it amorphous. To make it crystalline, it is heated to just below its melting point and held there for approximately 50ns, giving the atoms time to position themselves in their crystal locations. Once programmed, the memory state of the cell is determined by reading its resistance.

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