Low resistance peripheral contacts while maintaining DRAM array integrity
View Patent ↗An apparatus having low resistance contacts in both the memory cell array and peripheral logic circuitry areas of a semiconductor device, for example, a DRAM memory device, is disclosed. In a buried bit line connection process flow, the present invention utilizes chemical vapor deposition of titanium to form titanium silicide in contact structures of the peripheral logic circuitry areas and physical vapor deposition to provide a metal mode (metallic) titanium layer in contact with the poly plugs in the memory cell array area of a semiconductor device, for example, a DRAM memory device according to the present invention. In this manner, the present invention avoids the potential drawbacks such as voiding in the poly plugs of the memory cell array due to the present of titanium silicide, which can cause significant reduction of device drain current and in extreme cases cause electrical discontinuity.
1. A memory device, comprising:
a substrate having a memory cell array area and a peripheral circuitry area, wherein said memory cell array area comprises at least one polysilicon plug;
an insulating layer provided over said substrate;
at least one periphery contact defined in material layers over said substrate at said periphery circuitry area of said substrate, wherein said material layers is at least said insulating layer, said peripheral contact having a low resistance metal film layer provided over a portion of said insulating layer, along bottom and opposing sidewall edges of the periphery contact and forming metal silicide in contact with said substrate; and
at least one memory cell array contact defined in said material layers over said substrate at said memory cell array area of said substrate, and having a metal mode film layer in direct physical contact with said at least one polysilicon plug the metal mode film layer being over and in direct contact with the low resistance metal film layer in the peripheral circuitry area; and
a tungsten nitride layer provided on and in physical contact with said metal mode film layer such that said tungsten nitride layer inhibits formation of metal silicide on said at least one polysilicon plug.
2. A memory device as in claim 1 , wherein said at least one periphery contact includes said metal mode film layer provided on said low resistance metal film layer.
3. A memory device as in claim 1 , wherein said at least one periphery contact further includes said tungsten nitride layer and layers of tungsten and metal nitrides provided over said metal mode film layer.
4. A memory device as in claim 1 , wherein said at least one periphery contact includes said metal mode film layer provided on said low resistance metal film layer, said further includes said tungsten nitride layer and layers of tungsten and metal nitrides provided over said metal mode film layer.
5. A memory device as in claim 1 , wherein said at least one memory cell array contact further include layers of tungsten and metal nitrides provided over said tungsten nitride layer.
6. A memory device as in claim 1 , wherein said metal mode film layer is provided on said low resistance metal film layer, said at least one periphery contact includes said tungsten nitride layer, and said at least one periphery contact and said at least one memory cell array contact further include layers of tungsten and metal nitrides provided over said metal mode film layer.
7. A memory device as in claim 1 , wherein said low resistance metal film layer is a chemical vapor deposited metal film.
8. A memory device as in claim 1 , wherein said low resistance metal film layer is chemical vapor deposited titanium.
9. A memory device as in claim 1 , wherein the low resistance metal mode film has a thickness ranging from about 1 Angstrom to about 5000 Angstroms.
10. A memory device as in claim 1 , wherein said low resistance metal film layer is titanium, and said metal silicide is titanium silicide (TiSix).
11. A memory device as in claim 1 , wherein said metal mode film layer is physical vapor deposited titanium.
12. A memory device as in claim 1 , wherein said insulating layer has a thickness ranging from about 5 Angstroms to about 10,000 Angstroms.
13. A memory device as in claim 1 , wherein said low resistance metal film layer is titanium deposited by a first deposition method, and said metal mode film layer is titanium deposited by second deposition method different from said first deposition method.
14. A memory device as in claim 1 , wherein said low resistance metal film layer is deposited by chemical vapor deposition, and said metal mode film layer is deposited by physical vapor deposition.
15. A memory device as in claim 1 , wherein said low resistance metal film layer is titanium deposited by chemical vapor deposition, and said metal mode film layer is titanium deposited by physical vapor deposition.
16. A memory device as in claim 1 , wherein said at least one memory cell array contact has a film stack.
17. A memory device as in claim 1 , wherein said at least one memory cell array contact has a film stack, said metal mode film layer having a portion contacting said low resistance metal film layer.
18. A memory device as in claim 1 , wherein said at least one memory cell array contact has a film stack comprising said metal mode film layer, said tungsten nitride layer, and a layer of tungsten.
19. A memory device as in claim 1 , wherein said at least one memory cell array contact has a film stack comprising said metal mode film layer, said tungsten nitride layer, and a layer of tungsten, said metal mode film layer having a portion contacting said low resistance metal film layer.
20. A memory device as in claim 1 , wherein said insulating layer comprises tetraethylorthosilicate (TEOS), other oxides, and combinations thereof.
21. A memory device as in claim 1 , wherein said peripheral circuitry area is an N-channel transistor area, a P-channel transistor area, and combinations thereof.
22. A memory device as in claim 1 , wherein said memory cell array area comprises gate stacks having an oxide layer, a conductive gate layer provided on said oxide layer, an insulating cap layer, and insulating sidewalls adjacent said at least one polysilicon plug.
23. A memory device, comprising:
a substrate having a memory cell array area and a peripheral circuitry area, wherein said memory cell array area comprises at least one polysilicon plug;
an insulating layer provided over said substrate;
at least one periphery contact defined in material layers over said substrate at said periphery circuitry area of said substrate, wherein said material layers is at least said insulating layer, said peripheral contact having a low resistance metal film layer provided over a portion of said insulating layer, along bottom and sidewall edges of the periphery contact and forming metal silicide in contact with said substrate;
at least one memory cell array contact defined in said material layers over said substrate at said memory cell array area of said substrate, and having a metal mode film layer in direct physical contact with said at least one polysilicon plug; and
a tungsten nitride layer provided on and in physical contact with said metal mode film layer such that said tungsten nitride layer inhibits formation of metal silicide on said at least one polysilicon plug,
wherein said at least one periphery contact includes said metal mode film layer provided on and in direct physical contact with said low resistance metal film layer, and wherein the metal mode film has a thickness ranging from about 1 Angstrom to about 5000 Angstroms and is titanium, and said metal silicide is titanium silicide (TiSix).
24. A memory device, comprising:
a substrate having a memory cell array area and a peripheral circuitry area, wherein said memory cell array area comprises at least one polysilicon plug;
an insulating layer provided over said substrate;
at least one periphery contact defined in material layers over said substrate at said periphery circuitry area of said substrate, wherein said material layers is at least said insulating layer, said peripheral contact having a low resistance metal film layer provided over a portion of said insulating layer, along sidewall and bottom edges of the periphery contact and forming metal silicide in contact with said substrate;
at least one memory cell array contact defined in said material layers over said substrate at said memory cell array area of said substrate, and having a metal mode film layer in direct physical contact with said at least one polysilicon plug;
a tungsten nitride layer provided on and in physical contact with said metal mode film layer such that said tungsten nitride layer inhibits formation of metal silicide on said at least one polysilicon plug,
wherein said at least one periphery contact includes said metal mode film layer provided on and in direct physical contact with said low resistance metal film layer, wherein the metal mode film has a thickness ranging from about 1 Angstrom to about 5000 Angstroms and is titanium, said metal silicide is titanium silicide (TiSix), and said at least one memory cell array contact has a film stack comprising said metal mode film layer, said tungsten nitride layer, and a layer of tungsten, said metal mode film layer having a portion contacting said low resistance metal film layer.