National Institute of Advanced Industrial Science and Technology

Elpida Memory, Inc.

Alexander Kolobov

Junji Tominaga

Paul Fons

Robert Simpson

Isamu Asano

Takayuki Shima

James Paul Fons

Kazuo Aizawa

Reiko Kondo

Recording and erasing of data in PRAM have hitherto been performed based on a change in physical characteristics caused by primary phase-transformation of a crystalline state and an amorphous state of a chalcogen compound including Te which serves as a recording material. Since, however, a recording thin film is formed of a polycrystal but not a single crystal, a variation in resistance values occurs and a change in volume caused upon phase-transition has placed a limit on the number of times of readout of the record. In one embodiment, the above problem is solved by preparing a solid memory having a superlattice structure with a thin film containing Sb and a thin film containing Te. The solid memory can realize the number of times of repeated recording and erasing of 10.

Solid memory

Recording and erasing of data in PRAM have hitherto been performed based on a change in physical characteristics caused by primary phase-transformation of a crystalline state and an amorphous state of a chalcogen compound including Te which serves as a recording material. Since, however, a recording thin film is formed of a polycrystal but not a single crystal, a variation in resistance values occurs and a change in volume caused upon phase-transition has placed a limit on the number of times of readout of record. In one embodiment, the above problem is solved by preparing a solid memory having a superlattice structure of thin films including Ge and thin films including Sb. The solid memory can realize the number of times of repeated recording and erasing of 10.

A solid-state memory that requires a lower current during recording and erasing data and can repeatedly rewrite data an increased number of times. In at least one example embodiment, the solid-state memory includes a recording layer that includes a laminated structure in which electric properties are changed in response to a phase separation. The laminated structure includes a film containing an Sb atom(s) and a film containing a Ge atom(s), which films constitute a superlattice structure. In the laminated structure, phase separation of the film containing the Sb atom and the film containing the Ge atom allows data to be recorded and erased efficiently.

Superlattice recording layer for a phase change memory

A method of at least one embodiment of the present invention of manufacturing a solid-state memory is a method of manufacturing a solid-state memory, the solid-state memory including a recording film whose electric characteristics are varied by phase transformation, the method including: forming the recording film by forming a laminate of two or more layers so that a superlattice structure is provided, each of the layers having a parent phase which shows solid-to-solid phase-transformation, the recording film being formed at a temperature not lower than a temperature highest among crystallization temperatures of the parent phases. It is thus possible to manufacture a solid-state memory which requires lower current for recording and erasing data and has a greater rewriting cycle number.

Solid-state memory manufacturing method

A solid memory may include a recording layer including Ge, Sb and Te as major components. The recording layer may include a superlattice. The recording layer may include multi-layers each having a parent phase showing a phase transformation in solid-states, the phase transformation causing change in electrical property of the recording layer. The recording layer may include an SbTelayer that includes at least one period of a first lamination of a first Te-atomic layer, a first Sb-atomic layer, a second Te-atomic layer, a second Sb-atomic layer, and a third Te-atomic layer in these order, a GeTe layer that includes at least one period of a second lamination of a fourth Te-atomic layer and a Ge-atomic layer, and an Sb layer that includes a plurality of Sb-atomic layers.

Solid-state memory and semiconductor device

To include a superlattice laminate having laminated thereon a first crystal layer of which crystal lattice is a cubic crystal and in which positions of constituent atoms are reversibly replaced by application of energy, and a second crystal layer having a composition different from that of the first crystal layer, and an orientation layer that is an underlaying layer of the superlattice laminate and causes a laminated surface of the first crystal layer to be (111)-orientated. According to the present invention, the laminated surface of the first crystal layer can be (111)-orientated by using the orientation layer as an underlaying layer. In the first crystal layer of which laminated surface is (111)-orientated, a crystal structure reversibly changes when a relatively low energy is applied. Therefore, characteristics of a superlattice device having this crystal layer can be enhanced.

Superlattice device, manufacturing method thereof, solid-state memory including superlattice device, data processing system, and data processing device

A solid-state memory device includes: a superlattice laminate having plural crystal layers laminated therein, the crystal layers including first and second crystal layers having mutually opposite compositions; a lower electrode provided on a first surface in a laminating direction of the superlattice laminate; and an upper electrode provided on a second surface of the superlattice laminate in the laminating direction. The first crystal layer included in the superlattice laminate is made of a phase change compound. According to the present invention, the superlattice laminate laminated in opposite directions of the upper and lower electrodes is sandwiched between these electrodes. Therefore, when an electric energy is applied to the superlattice laminate via these electrodes, a uniform electric energy can be applied to a laminated surface of the superlattice laminate. Accordingly, fluctuation of a resistance is small even when information is repeatedly rewritten, and data can be read stably as a result.

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Tsukuba, Japan

Alexander Kolobov