Chalcogenide devices incorporating chalcogenide materials having reduced germanium or telluruim content

Abstract

A chalcogenide material and chalcogenide memory device having less stringent requirements for formation, improved thermal stability and / or faster operation. The chalcogenide materials include materials comprising Ge, Sb and Te in which the Ge and / or Te content is lean relative to the commonly used Ge2Sb2Te5 chalcogenide composition. Electrical devices containing the instant chalcogenide materials show a rapid convergence of the set resistance during cycles of setting and resetting the device from its as-fabricated state, thus leading to a reduced or eliminated need to subject the device to post-fabrication electrical formation prior to end-use operation. Improved thermal stability is manifested in terms of prolonged stability of the resistance of the device at elevated temperatures, which leads to an inhibition of thermally induced setting of the reset state in the device. Significant improvements in the 10 year data retention temperature are demonstrated. Faster device operation is achieved through an increased speed of crystallization, which acts to shorten the time required to transform the chalcogenide material from its reset state to its set state in an electrical memory device.

Description

FIELD OF INVENTION [0001] This invention pertains to chalcogenide materials having applications as electrical and optical memories and switches. More particularly, this invention relates to chalcogenide materials showing high reproducibility of electrical resistance upon transformation from a primarily amorphous state to a primarily crystalline state on repeated cycles and to chalcogenide materials exhibiting high thermal stability. Most specifically, this invention is concerned with off-tieline chalcogenide alloys in the Ge—Sb—Te family having a low Ge concentration. BACKGROUND OF THE INVENTION [0002] Chalcogenide materials are an emerging class of commercial electronic materials that exhibit switching, memory, logic, and processing functionality. The basic principles of chalcogenide materials were developed by S. R. Ovshinsky in the 1960's and much effort by him and others around the world since then have led to advancements of the underlying science and an expansion of the field ...

AI Technical Summary

Benefits of technology

"The invention provides a chalcogenide alloy composition that improves thermal stability and reduces the need for post-fabrication formation electrical stimulus in electrical chalcogenide memory applications. The alloy includes a combination of germanium (Ge) and selenium (Sb) with atomic concentrations of Ge ranging from 15% to 20% and Sb ranging from 30% to 50%. The alloy can also include tellurium (Te) with atomic concentrations ranging from 20% to 50%. The use of this alloy results in faster operation through shorter time-to-set characteristics and reduced number of electrical pulses required for device formation. The resistance of the device stabilizes in a fewer number of cycles of setting and resetting, and the thermal stability of data retention is improved. The alloy can be used in electrical devices containing a layer of chalcogenide material in electrical communication with two electrical terminals or contacts."

Problems solved by technology

A current issue in terms of the properties of chalcogenide materials is the need to improve the thermal stability of the materials.

Data in a chalcogenide material are retained as a structural state of the material, so any tendency of the structural state to transform with temperature represents a potential undesirable mechanism of erasing or losing data.

Many chalcogenide memory materials retain their structural states for long periods of time at room temperature, but become susceptible to variations in the structural state upon increasing temperature.

In practical terms, this limits the temperature environment in which chalcogenide memory devices can be utilized as well as the temperatures that can be employed in processing or manufacturing.

In practice, however, formation of the chalcogenide materials in current use requires many cycles of setting and resetting until the resistance of the set state stabilizes to a reproducible value.

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