Multiple bit chalcogenide storage device
View Patent ↗Multi-terminal chalcogenide memory cells having multiple binary or non-binary bit storage capacity and methods of programming same. The memory cells include a pore region containing a chalcogenide material along with three or more electrical terminals in electrical communication therewith. The configuration of terminals delineates spatially distinct regions of chalcogenide material that may be selectively and independently programmed to provide multibit storage. The application of an electrical signal (e.g. electrical current or voltage pulse) between a pair of terminals effects a structural transformation in one of the spatially distinct portions of chalcogenide material. Application of electrical signals to different pairs of terminals within a chalcogenide device effects structural transformations in different portions of the chalcogenide material. The structural states produced by the structural transformations may be used for storage of information values in a binary or non-binary (e.g. multilevel) system. The selection of terminals provides for the selective programming of specific and distinct portions within a continuous volume of chalcogenide material, where each selectively programmed portion provides for the storage of a single binary or non-binary bit. In devices having three or more terminals, two or more selectively programmable portions are present within the volume of chalcogenide material occupying the pore region and multibit storage is accordingly realized. The instant invention further includes methods of programming chalcogenide memory cells having three or more terminals directed at the storage of multiple bits of information in binary or non-binary systems.
1. A chalcogenide device comprising:
a chalcogenide material having a plurality of structural states, said structural states including accumulation states and greyscale states;
a first terminal in electrical communication with said chalcogenide material;
a second terminal in electrical communication with said chalcogenide material, said second terminal having a circumferential shape, said second terminal surrounding and in contact with said chalcogenide material;
a third terminal in electrical communication with said chalcogenide material;
wherein said chalcogenide material includes a first portion in a first structural state and a second portion in a second structural state, said first and second structural states being selected from among said accumulation states or said greyscale states, and wherein said second terminal is formed vertically between said first and third terminals.
2. The device of claim 1 , wherein said chalcogenide material comprises S, Se, or Te.
3. The device of claim 2 , wherein said chalcogenide material further comprises Ge or Sb.
4. The device of claim 2 , wherein said chalcogenide material further comprises As or Si.
5. The device of claim 2 , wherein said chalcogenide material further comprises an element selected from the group consisting of Al, In, Bi, Pb, Sn, P. and O.
6. The device of claim 2 , wherein said chalcogenide further comprises a transition metal.
7. The device of claim 1 , wherein the composition of said first portion of said chalcogenide material differs from the composition of said second portion of said chalcogenide material.
8. The device of claim 1 , wherein the resistance of said first structural state differs from the resistance of said second structural state.
9. The device of claim 1 , wherein said first and second structural states are selected from among said greyscale states.
10. The device of claim 1 , wherein said device stores two or more bits of information.
11. The device of claim 10 , wherein said bits are non-binary bits.
12. The device of claim 1 , wherein said chalcogenide material has a shape having a non-uniform cross section.
13. The device of claim 1 , further comprising one or more additional terminals in electrical communication with said chalcogenide material.
14. The device of claim 13 , wherein said chalcogenide material further includes a third portion in a third structural state said third structural state being selected from among said accumulation states or said greyscale states.
15. The device of claim 1 , wherein said second terminal has an annular shape.