Non-volatile memory with silicided bit line contacts
View Patent ↗An approach to use silicided bit line contacts that do not short to the underlying substrate in memory devices. The approach provides for silicide formation in the bit line contact area, using a process that benefits from being self-aligned to the oxide-nitride-oxide (ONO) nitride edges. A further benefit of the approach is that the bit line contact implant and rapid temperature anneal process can be eliminated. This approach is applicable to embedded flash, integrating high density devices and advanced logic processes.
1. A method comprising:
disposing a first dielectric layer on a substrate;
disposing a dielectric charge trapping layer on the first dielectric layer;
disposing a second dielectric layer on the dielectric trapping layer;
patterning a hard mask on the second dielectric layer;
disposing an oxide spacer on sidewalls of the hard mask to leave exposed a bit line contact region;
removing portions of the second dielectric layer, dielectric trapping layer and first dielectric layer within the bit line contact region;
removing portions of the oxide spacer to leave exposed a portion of the second dielectric layer; and
removing the exposed portion of the second dielectric layer to thereby yield extended portions of the dielectric trapping layer and first dielectric layer.
2. The method of claim 1 , wherein the first dielectric layer comprises silicon dioxide.
3. The method of claim 1 , wherein the dielectric charge trapping layer comprises silicon-rich nitride (SiRN).
4. The method of claim 1 , wherein the second dielectric layer comprises silicon oxide.
5. The method of claim 1 , further comprising:
forming a metalized portion within the bit line contact region.
6. The method of claim 5 , wherein the metallized portion comprises a silicide.
7. The method of claim 6 , wherein the silicide comprises at least one of titanium silicide, cobalt silicide and nickel silicide.
8. The method of claim 5 , wherein forming the metalized portion within the bit line contact region includes forming the metalized portion in a trench-like configuration.
9. The method of claim 1 , wherein disposing the oxide spacer includes disposing the oxide spacer that comprises at least one of a tetraethylorthosilicate (TEOS) oxide, a high temperature oxide (HTO), or an atomic layer deposition (ALD)-formed oxide.
10. The method of claim 1 , wherein removing portions of the second dielectric layer, dielectric trapping layer and first dielectric layer within the bit line contact region includes using a selective etch having an etch rate of the oxide spacer that is substantially lower than an etch rate of the second dielectric layer, dielectric trapping layer and first dielectric layer.
11. The method of claim 1 , wherein removing portions of the oxide spacer to leave exposed a portion of the second dielectric layer includes using an oxide wet etch.
12. The method of claim 1 , further comprising:
forming a bit line implant region in the substrate within the bit line contact region.
13. The method of claim 12 , wherein forming the bit line implant region further comprises:
implanting a first bit line implant sub-region within the bit line contact region using an n-type dopant;
reducing a width of the oxide spacer; and
implanting a second bit line implant sub-region within the bit line contact region using the n-type dopant, wherein implanting the second bit line implant sub-region uses a lower energy than implanting the first bit line implant sub-region.
14. The method of claim 13 , wherein the n-type dopant comprises at least one of arsenic, phosphorous and antimony.
15. The method of claim 13 , wherein at least one of implanting the first bit line implant sub-region and implanting the second bit line implant uses at an energy level of 40 keV to 50 keV.
16. The method of claim 13 , wherein at least one of implanting the first bit line implant sub-region and implanting the second bit line implant uses doses in a range of 1×10 15 to 1.5×10 15 atoms/cm 2 .
17. The method of claim 1 , further comprising:
forming a word line that is oriented substantially at right angles to a bit line within the bit line contact region.
18. The method of claim 17 , further comprising:
removing the hard mask prior to forming the word line.
19. The method of claim 1 , further comprising:
forming a bit line dielectric layer within the bit line contact region.
20. The method of claim 19 , wherein the bit line dielectric layer comprises a high density plasma (HDP) oxide.