Methods and apparatus for resistance variable material cells
View Patent ↗The present invention is related to methods and apparatus to produce a memory cell or resistance variable material with improved data retention characteristics and higher switching speeds. In a memory cell according to an embodiment of the present invention, silver selenide and a chalcogenide glass, such as germanium selenide (Ge x Se (1−x) ) are combined in an active layer, which supports the formation of conductive pathways in the presence of an electric potential applied between electrodes. Advantageously, embodiments of the present invention can be fabricated with relatively wide ranges for the thicknesses of the silver selenide and glass layers.
1. A memory cell comprising:
a first electrode;
a second electrode, where the first electrode and the second electrode provide access to the memory cell; and
a memory cell body disposed between the first electrode and the second electrode, where the memory cell body comprises a layer of inter-mixed silver selenide and germanium selenide (Ge x Se (1−x) ), wherein said layer has substantially no silver dispersed therein except where present in a conductive pathway.
2. The memory cell as defined in claim 1 , wherein x is in the range of about 0.2 to about 0.43.
3. The memory cell as defined in claim 1 , wherein the germanium selenide (Ge x Se (1−x) ) is Ge 0.40 Se 0.60 .
4. The memory cell as defined in claim 1 , wherein germanium selenide (Ge x Se (1−x) ) is Ge 0.25 Se 0.75 .
5. The memory cell as defined in claim 1 , wherein the memory cell body is from about 1:1 to about 5:1 silver selenide to germanium selenide (Ge x Se (1−x) ).
6. The memory cell as defined in claim 1 , wherein the memory cell body is from about 1.43:1 to about 2:1 silver selenide to germanium selenide (Ge x Se (1−x) ).
7. The memory cell as defined in claim 1 , wherein the memory cell body is from about 1.72:1 to about 1.75:1 silver selenide to germanium selenide (Ge x Se (1−x) ).
8. A memory device, comprising:
a memory body between a first and a second electrode, said memory body comprising a plurality of layers;
a first layer of said plurality of layers being silver selenide;
a second layer of said plurality of layers being germanium selenide;
a third layer of said plurality of layers being silver.
9. The memory device of claim 8 , wherein said first layer is between said second and third layers.
10. The memory device of claim 8 , wherein said second layer is between said first and third layers.
11. The memory device of claim 8 , wherein said germanium selenide is a rigid glass.
12. The memory device of claim 8 , wherein neither of said first and second electrodes comprises silver.