Phase change memory element with a peripheral connection to a thin film electrode and method of manufacture thereof

Abstract

A PCM cell structure comprises a first electrode, a phase change element, and a second electrode, wherein the phase change element is inserted in between the first electrode and the second electrode and only the peripheral edge of one of the first and second electrodes contacts the phase change element thereby reducing the contact area between the phase change element and one of the electrodes thereby increasing the current density through the phase change element and effectively inducing the phase change at a first programming power.

Description

FIELD OF THE INVENTION [0001] The present invention relates to memory devices, and more particularly a Phase Change Memory (PCM) cell structure and methods of making and using the same. BACKGROUND [0002] Recently nonvolatile chalcogenide Random Access Memory (RAM) devices, made of the germanium-antimony-tellurium (Ge2Sb2Te5) chalcogenide material, have been regarded as the most promising next-generation memory devices. The term “chalcogen” refers to the Group VI elements of the periodic table; and the term “chalcogenide” refers to alloys containing at least one of these elements, e.g. the alloy of germanium, antimony, and tellurium, etc. Chalcogenide materials have been used in PCM devices, especially in both rewritable Compact Disk (CD) and Digital Video Disk or Digital Versatile Disc (DVD) devices. This kind of memory when introduced into semiconductor chips has many advantages over others in areas, e.g. scalability, high sensing margin, low energy consumption, and cycling enduran...

AI Technical Summary

Benefits of technology

[0027] Because effective heating of the phase change material requires only a high current density, reducing the contact area between the phase change material and one of the electrodes is sufficient to manage the power requirements. Thus, for example, good performance can be obtained from a long, narrow cylinder of phase change material, because the cross-sectional area is small even if the length, and therefore total volume of material, is large. Similarly, a conical or pyramidal structure can form an efficient PCM cell if the contact area between one electrode and the phase change material is small.

Problems solved by technology

However, the crystallization speed of a germanium-antimony-tellurium material tends to decrease with thinner films.

If the dimensions vary excessively, on an all-cells / all-die / all-days basis, there is a risk that the current applied during the Reset pulse may actually set the material in some cells, and vice-versa.

Thus, the principal challenge in fabricating practical memory devices is in producing and controlling dimensions well below the norms for standard photolithography.

When current is flowing through the electrodes, the current density at the tapered contact is very high leading to a rapid rise of temperature there.

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