Phase-change memory

Abstract

A phase-change memory (10) for the non-volatile storage of binary contents stores the binary contents electrically and/or optically in a non-volatile manner by locally switching a material (18) between an amorphous and a crystalline phase. The state with respect to the electrical conductivity of the material (18) and/or the reflection properties of the material (18) determines the information content of the phase-change memory (10). A method for non-volatile storage of binary contents in a phase-change memory (10), which stores the binary contents electrically and/or optically in a non-volatile manner by locally switching a material (18) between an amorphous and a crystalline phase, whereby the state with respect to the electrical conductivity of the material (18) and/or the reflection properties of the material (18) determines the information content of the phase-change memory (10).

Claims

1-9. (canceled)

10. A phase-change memory (10) for non-volatile storage of binary contents, wherein the phase-change memory (10) stores the binary contents electrically and/or optically in a non-volatile manner by locally switching a material (18) between an amorphous and a crystalline phase, wherein a state with respect to an electrical conductivity of the material (18) and/or reflection properties of the material (18) determines an information content of the phase-change memory (10), and wherein a sound generator is provided, which exposes the material (18) to sound before or at least during the switching.

11. The phase-change memory (10) for the non-volatile storage of binary contents according to claim 10, wherein the sound generator is designed as an ultrasonic generator (26).

12. The phase-change memory (10) for the non-volatile storage of binary contents according to claim 11, wherein the ultrasonic generator (26) has a piezoelectric unit (28).

13. The phase-change memory (10) for the non-volatile storage of binary contents according to claim 10, further comprising control means for variably adjusting a frequency of the sound.

14. The phase-change memory (10) for the non-volatile storage of binary contents according to claim 13, wherein the sound is an ultrasound, and wherein the control means adjusts the frequency of the ultrasound depending on a temperature and/or material.

15. The phase-change memory (10) for the non-volatile storage of binary content according to claim 10, wherein a plurality of phase stages of the material (18) are provided between the amorphous and crystalline phase for multi-stage switching when storing content.

16. A method for storing non-volatile binary contents in a phase-change memory (10), wherein the phase-change memory (10) stores the binary contents electrically and/or optically in a non-volatile manner by locally switching a material (18) between an amorphous and a crystalline phase, wherein a state with respect to an electrical conductivity of the material (18) and/or reflection properties of the material (18) determines an information content of the phase-change memory (10), comprising: generating sound, and exposing the material to the sound before or at least during the switching.

17. The method according to claim 16, wherein the sound is generated by a piezoelectric unit (28).

18. The method according to claim 16, wherein generating sounds comprises generating ultrasound, and wherein exposing the material to the sound before or at least during the switching comprises exposing the material to the ultrasound.

19. The method according to claim 18, wherein the ultrasound is generated by a piezoelectric unit (28).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 shows the structure of a phase-change memory with an ultrasonic generator.

DETAILED DESCRIPTION

[0026] In FIG. 1, 10 denotes the phase-change memory. The phase-change memory 10 comprises a first electrode 12 and a second electrode 14. A layer 16 of a phase-change material 18 is provided between the electrodes 12, 14. The electrode 12, the phase-change material 18, and the electrode 14 form a first functional area 20 of the phase-change memory 10, which is indicated by a curly bracket. This first functional area 20 is arranged on an insulating layer 22 belonging to this functional area 20.

[0027] A second functional area 24, which is also identified by a curly bracket, comprises an ultrasonic generator 26. This second functional area 24 adjoins the insulating layer 22 of the first functional area 20. The ultrasonic generator 26 comprises a piezoelectric crystal layer 28, which is controlled by two further electrodes 30, 32. An insulating layer 33 and a third functional area 34 adjoin the piezoelectric crystal layer 28.

[0028] The third functional area 34 comprises a heating layer 36 and two electrodes 38, 40. The third functional area is indicated by an additional curly bracket. The heating layer 36 is operated via the two heating electrodes 38, 40. This third functional area comprises a silicon oxide layer 42 and adjoins a final substrate layer 44.

[0029] The electrodes 12, 14 switch the phase-change material 18 depending on the current pulse and its duration.

[0030] The phase-change memory 10 exploits the fact that the phase-change material 18 has different electrical properties in the amorphous phase and in the crystalline phase. The electrical resistance is significantly greater in the amorphous state than in the crystalline state of the phase-change material 18. A current pulse is applied to the phase-change material 18 of the phase-change memory 10 via the two electrodes 12, 14. When a relatively high and short current pulse is applied to the phase-change material 18, it changes from the crystalline to the amorphous phase. After the end of the current pulse, the phase-change material 18 cools down very quickly. The phase-change material 18 remains in the amorphous state and does not return to the crystalline phase.

[0031] The phase-change material 18 returns from the amorphous state to the crystalline state by exposing it to a relatively low current pulse for a longer period of time. The process of switching from the amorphous to the crystalline state can thus be reversed based on the duration of the current pulse. As a result of the longer pulse duration, the amorphous material is heated to a temperature above the crystallization temperature and is maintained at this temperature until crystallization takes place. The process can be accelerated by applying ultrasound to the phase-change material 18 before or at least during the individual switching processes. With the piezoelectric layer 28, the ultrasonic generator 26 generates an ultrasonic field, which is matched to the phase-change material 18 and which acts on the phase-change material 18 and stimulates it accordingly. This accelerates the switching process of the phase-change material 18 considerably. Since the switching process of the phase-change material 18 is temperature-dependent in particular, the ultrasound is absorbed differently depending on the temperature. Control means, which are not shown here, are therefore provided that optimize the frequency of the ultrasound with respect to the temperature of the phase-change material 18.

[0032] The binary information contained by such a phase-change memory 10 is read by applying a voltage, for example across the electrodes. Depending on the state—amorphous or crystalline—of the phase-change material 18, a different current will flow, which is then utilized for reading. A binary state can thus be determined based on the resistance of the phase-change memory 10. The crystalline state is defined to be a binary “one”, and the amorphous state is defined to be a binary “zero”.

LIST OF REFERENCE SIGNS

[0033] 10 Phase-change memory [0034] 12 First electrode [0035] 14 Second electrode [0036] 16 Layer [0037] 18 Phase-change material [0038] 20 First functional area [0039] 22 Insulating layer [0040] 24 Second functional area [0041] 26 Ultrasonic generator [0042] 28 Piezoelectric crystal layer [0043] 30 Electrode for ultrasonic generator [0044] 32 Electrode for ultrasonic generator [0045] 33 Insulating layer [0046] 34 Functional area [0047] 36 Heating layer [0048] 38 Electrode for heating layer [0049] 40 Electrode for heating layer [0050] 42 Silicon oxide layer [0051] 44 Substrate