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

[0010] The instant invention provides a chalcogenide alloy composition that, when used in electrical chalcogenide memory applications, provides for greater thermal stability and / or reduced need for or elimination of post-fabrication formation electrical stimulus and / or faster operation through shorter time-to-set characteristics.

[0015] In some embodiments, the number of electrical pulses required for the formation of devices that incorporate the instant chalcogenide alloys is reduced or eliminated. In one embodiment, formation of the device in its as-fabricated (virgin) state requires no more than one step of resetting the device and one step of setting the device. In a more preferred embodiment, no formation of the device in its as-fabricated (virgin) state is required.

[0017] In still other embodiments, the thermal stability of data retention is improved. In one embodiment, the instant alloy has a thermal stability sufficient to provide for 10 year data retention at a temperature of at least 120° C. In a preferred embodiment, the alloy has a thermal stability sufficient to provide for 10 year data retention at a temperature of at least 130° C. In a more preferred embodiment, the alloy has a thermal stability sufficient to provide for 10 year data retention at a temperature of at least 140° C.

[0018] In yet other embodiments, the speed of device operation is improved through a decrease in the the time required to set the device. In one embodiment, the time required to set a device including as an active layer a chalcogenide material according to the instant invention is less than or equal to 75% of the time required to set the same device when Ge22.2Sb22.2Te55.5 is used as the active chalcogenide layer. In a preferred embodiment, the time required to set a device including as an active layer a chalcogenide material according to the instant invention is less than or equal to 50% of the time required to set the same device when Ge22.2Sb22.2Te55.5 is used as the active chalcogenide layer. In a more preferred embodiment, the time required to set a device including as an active layer a chalcogenide material according to the instant invention is less than or equal to 30% of the time required to set the same device when Ge22.2Sb22.2Te55.5 is used as the active chalcogenide layer.

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.

Images