Phase change memory structures

1. A phase change memory structure, comprising:

a phase change material layer;

a top electrode layer above the phase change material layer;

a metal silicon nitride layer in contact with the top electrode layer opposite from the phase change material layer;

a metal silicide layer in contact with the metal silicon nitride layer opposite from the top electrode layer; and

a conductive metal bit line in contact with the metal silicide layer opposite from the metal silicon nitride layer.

2. The memory structure of claim 1 , wherein the metal silicon nitride layer, metal silicide layer, and conductive metal bit line comprise tungsten, tantalum, niobium, molybdenum, titanium, or a combination thereof.

3. The memory structure of claim 1 , wherein the metal silicon nitride layer is formed of tungsten silicon nitride, wherein the metal silicide layer is formed of tungsten silicide, and wherein the conductive metal bit line is formed of tungsten.

4. The memory structure of claim 1 , wherein the conductive metal bit line has a thickness of 100 Å to 1000 Å.

5. The memory structure of claim 1 , wherein the conductive metal bit line has a tensile stress of 500 MPa to 3000 MPa.

6. The memory structure of claim 1 , wherein the conductive metal bit line has a line width roughness of 2 Å to 200 Å.

7. The memory structure of claim 1 , wherein the conductive metal bit line has a surface roughness of 2 Å to 200 Å.

8. The memory structure of claim 1 , wherein the conductive metal bit line has a resistivity of 5.6 μΩ-cm to 50 μΩ-cm.

9. The memory structure of claim 1 , wherein the metal silicide layer has a thickness of 10 Å to 300 Å.

10. The memory structure of claim 1 , wherein the metal silicide layer comprises tungsten silicide, tantalum silicide, niobium silicide, molybdenum silicide, titanium silicide, or a combination thereof.

11. The memory structure of claim 1 , wherein the metal silicide layer comprises tungsten silicide having a general formula of WSi x where x is from 1 to 3.

12. The memory structure of claim 1 , wherein the metal silicon nitride layer has a thickness of 10 Å to 300 Å.

13. The memory structure of claim 1 , wherein the metal silicon nitride layer comprises tungsten silicon nitride, tantalum silicon nitride, niobium silicon nitride, molybdenum silicon nitride, titanium silicon nitride, or a combination thereof.

14. The memory structure of claim 1 , wherein the top electrode layer comprises a carbon-containing material.

15. The memory structure of claim 1 , wherein the top electrode layer has a thickness of 10 Å to 500 Å.

16. A phase change memory system, comprising:

an array of memory cells arranged in rows and columns, wherein the memory cells comprise a phase change material layer and a top electrode layer above the phase change material layer;

a dielectric material electrically insulating the memory cells one from another;

a plurality of metal silicon nitride layers in contact with the top electrode layer of the plurality of memory cells;

a plurality of metal silicide layers in contact with the plurality of metal silicon nitride layers;

a plurality of conductive metal bit lines in contact with the plurality of metal silicon nitride layers, wherein the conductive metal bit lines extend along the columns to electrically connect each bit line to a column of memory cells;

a plurality of word lines in contact with a bottom surface of the memory cells, wherein the word lines extend along the rows to electrically connect each word line to a row of memory cells; and

a read/write controller electrically coupled to the plurality of word lines and the plurality of conductive metal bit lines, the read/write controller being operable to perform read and write operations to and from the array of memory cells via the plurality of word lines and the plurality of conductive metal bit lines.

17. The system of claim 16 , wherein the metal silicon nitride layers, metal silicide layers, and conductive metal bit lines comprise tungsten, tantalum, niobium, molybdenum, titanium, or a combination thereof.

18. The memory structure of claim 16 , wherein the metal silicon nitride layers are formed of tungsten silicon nitride, wherein the metal silicide layers are formed of tungsten silicide, and wherein the conductive metal bit lines are formed of tungsten.

19. The system of claim 16 , wherein the metal silicon nitride layers and the metal silicide layers are continuous layers extending along the columns to electrically connect each metal silicon nitride layer and metal silicide layer to a column of memory cells.

20. The system of claim 16 , wherein the metal silicide layers comprise tungsten silicide, tantalum silicide, niobium silicide, molybdenum silicide, titanium silicide, or a combination thereof.

21. The system of claim 16 , wherein the metal silicide layers comprise tungsten silicide having a general formula of WSi x where x is from 1 to 3.

22. The system of claim 16 , wherein the metal silicon nitride layers comprise tungsten silicon nitride, tantalum silicon nitride, niobium silicon nitride, molybdenum silicon nitride, titanium silicon nitride, or a combination thereof.

23. The system of claim 16 , wherein the top electrode layers comprise a carbon-containing material.

24. A method of making a phase change memory structure, comprising:

depositing material layers including a phase change material layer and a top electrode layer above the phase change material layer;

dividing the material layers into a plurality of memory cells separated by dielectric material;

depositing a metal silicon nitride layer over the top electrode layer;

depositing a metal silicide layer over the metal silicon nitride layer; and

depositing a conductive metal bit line over the metal silicide layer.

25. The method of claim 24 , wherein depositing the conductive metal bit line comprises depositing with a bias power and deposition pressure sufficient to provide a conductive metal bit line having a resistivity of 5.6 μΩ-cm to 50 μΩ-cm.