Junction leakage suppression in memory devices
A memory device includes a substrate and source and drain regions formed in the substrate. The source and drain regions include both phosphorous and arsenic and the phosphorous may be implanted prior to the arsenic. The memory device also includes a first dielectric layer formed over the substrate and a charge storage element formed over the first dielectric layer. The memory device may further include a second dielectric layer formed over the charge storage element and a control gate formed over the second dielectric layer.
1. A memory device, comprising:
a substrate;
a source region formed in the substrate, the source region comprising phosphorous and arsenic, where the phosphorous in the source region is formed to a depth ranging from about 2,000 Å to about 2,500 Å below an upper surface of the substrate and the arsenic in the source region is formed to a depth ranging from about 1,000 Å to about 1,500 Å below the upper surface of the substrate, and the phosphorous in the source region is formed to a greater depth below the upper surface of the substrate than the arsenic in the source region, where the source region has a greatest width at an upper portion that is adjacent the upper surface of the substrate, and a smallest width at a deepest portion with respect to the upper surface of the substrate, and where the deepest portion of the source region includes only the phosphorous and the upper portion of the source region includes a combination of the phosphorous and the arsenic, and where the deepest portion of the source region has a smaller width than the upper portion;
a drain region formed in the substrate, the drain region comprising phosphorous and arsenic, where the phosphorous in the drain region is formed to a depth ranging from about 1,000 Å to about 2,500 Å below the upper surface of the substrate and the arsenic in the drain region is formed to a depth ranging from about 500 Å to about 1,500 Å below the upper surface of the substrate, and the phosphorous in the drain region is formed to a greater depth below the upper surface of the substrate than the arsenic in the drain region, where the drain region has a greatest width at an upper portion that is adjacent the upper surface of the substrate and a smallest width at a deepest portion with respect to the upper surface of the substrate, and where the deepest portion of the drain region includes only the phosphorous and the upper portion of the drain region includes a combination of the phosphorous and the arsenic, and where the deepest portion of the drain region has a smaller width than the upper portion;
a first dielectric layer formed over the substrate;
a charge storage element formed over the first dielectric layer;
a second dielectric layer formed over the charge storage element;
a control gate formed over the second dielectric layer;
a first isolation region located adjacent to the deepest portion of the source region, the deepest portion of the source region preventing leakage currents from being generated at the junction near the first isolation region, where the first isolation region comprises an oxide and a field oxide;
a first silicide layer formed over the source region, the first silicide layer wrapping around and extending to a greater depth, into the source region, in an area adjacent to the first isolation region than in other areas of the source region, where the area adjacent to the first isolation region is smaller than the other areas of the source region;
a second isolation region located adjacent to the deepest portion of the drain region, the deepest portion of the drain region preventing leakage currents from being generated at the junction near the second isolation region, where the second isolation region comprises an oxide and a field oxide; and
a second silicide layer formed over the drain region, the second silicide layer wrapping around and extending to a greater depth, into the drain region, in an area adjacent to the second isolation region than in other areas of the drain region, where the area adjacent to the second isolation region is smaller than the other areas of the drain region.
2. The memory device of claim 1 , where the phosphorous in the source and drain regions is implanted before the arsenic.
3. The memory device of claim 1 , where the phosphorous is implanted in the source and drain regions prior to the arsenic at a dosage ranging from about 1×10 14 atoms/cm 2 to about 3×10 14 atoms/cm 2 and an implantation energy ranging from 60 KeV to about 70 KeV.
4. The memory device of claim 3 , where the arsenic is implanted at a dosage ranging from about 1×10 15 atoms/cm 2 to about 5×10 15 atoms/cm 2 and an implantation energy ranging from about 30 KeV to about 70 KeV.
5. The memory device of claim 1 , where the charge storage element comprises a nitride.
6. A method of manufacturing a semiconductor device, comprising:
forming a memory cell, the memory cell including a tunnel oxide layer formed on a substrate, a charge storage element, an inter-gate dielectric and a control gate;
implanting phosphorous and arsenic in the substrate to form a source region and a drain region, where the phosphorous is implanted to a depth ranging from about 2,000 Å to about 2,500 Å below an upper surface of the substrate and is implanted at a dosage ranging from 6×10 13 atoms/cm 2 to about 3×10 14 atoms/cm 2 and the arsenic is implanted to a depth ranging from about 1,000 Å to about 1,500 Å below the upper surface of the substrate, and the phosphorous is implanted to a greater depth below the upper surface of the substrate than the arsenic before implanting the arsenic, where a deepest portion of the source region includes only phosphorous and prevents leakage currents from being generated at a junction near a first isolation region and a deepest portion of the drain region includes only phosphorous and prevents leakage currents from being generated at a junction near a second isolation region;
forming the first isolation region adjacent to the source region from a combination of an oxide and a field oxide;
forming one first silicide layer over the source region, the first silicide layer wrapping around and extending to a greater depth, into the source region, in an area adjacent to the first isolation region than in other areas of the source region, where the area adjacent to the first isolation region is smaller than the other areas of the source region;
forming the second isolation region adjacent to the drain region from a combination of the oxide and the field oxide; and
forming a second silicide layer over the drain region during an annealing process, the second silicide layer wrapping around and extending to a greater depth, into the drain region, in an area adjacent to the second isolation region than in other areas of the drain region, where the area adjacent to the second isolation region is smaller than the other areas of the drain region.
7. The method of claim 6 , where the phosphorous is implanted at an implantation energy ranging from about 50 KeV to about 70 KeV.
8. The method of claim 7 , where the arsenic is implanted at a dosage ranging from about 1×10 15 atoms/cm 2 to about 5×10 15 atoms/cm 2 and an implantation energy ranging from about 30 KeV to about 70 KeV.
9. A non-volatile memory device, comprising:
a plurality of memory cells, each of the memory cells including:
a dielectric layer formed on a substrate,
a charge storage element formed on the dielectric layer,
an inter-gate dielectric formed on the charge storage element,
a control gate formed over the inter-gate dielectric,
a source region formed in the substrate having one location deeper than another location in the substrate, the source region comprising phosphorous and arsenic,
a drain region formed in the substrate having one location deeper than another location in the substrate, the drain region comprising phosphorous and arsenic,
where the phosphorous in the source and drain regions is implanted to a depth ranging from about 1,000 Å to about 2,500 Å below an upper surface of the substrate and the arsenic in the source and drain regions is implanted to a depth ranging from about 500 Å to about 1,500 Å below the upper surface of the substrate, where the phosphorous in the source and drain regions is implanted to a greater depth below the upper surface of the substrate than the arsenic in the source and drain regions,
a first isolation region located adjacent to a deepest location of the source region, the deepest location of the source region preventing leakage currents from being generated at the junction near the first isolation region, where the first isolation region comprises a combination of an oxide and a field oxide;
a first silicide layer formed over the source region, the first silicide layer wrapping around and extending to a greater depth, into the source region, in an area adjacent to the first isolation region than in other areas of the source region, where the area adjacent to the first isolation region is smaller than the other areas of the source region;
a second isolation region located adjacent to a deepest location of the drain region, the deepest location of the drain region preventing leakage currents from being generated at the junction near the second isolation region, where the second isolation region comprises a combination of the oxide and the field oxide; and
a second silicide layer formed over the drain region, the second silicide layer wrapping around and extending to a greater depth, into the drain region, in an area adjacent to the second isolation region than in other areas of the drain region, where the area adjacent to the second isolation region is smaller than the other areas of the drain region.
10. The non-volatile memory device of claim 9 , where the phosphorous in the source and drain regions is implanted before the arsenic.
11. The non-volatile memory device of claim 10 , where the phosphorous is implanted in the source and drain regions at a dosage ranging from about 6×10 13 atoms/cm 2 to about 3×10 14 atoms/cm 2 and an implantation energy ranging from about 50 KeV to about 70 KeV.
12. The non-volatile memory device of claim 11 , where the arsenic is implanted in the source and drain regions at a dosage ranging from about 1×10 15 atoms/cm 2 to about 5×10 15 atoms/cm 2 and an implantation energy ranging from about 30 KeV to about 70 KeV.
13. The non-volatile memory device of claim 9 , where the first and second silicide layers comprise cobalt silicide.
14. The method of claim 6 , where implanting the phosphorous and the arsenic to form the source region and the drain region comprises:
forming the source region having a greatest width at an upper portion that is adjacent the upper surface of the substrate and a smallest width at a deepest portion of the source region, where the deepest portion of the source region includes the phosphorous and none of the arsenic, the upper portion of the source region includes a combination of the phosphorous and the arsenic, and the deepest portion of the source region has a smaller width than the upper portion of the source region, and
forming a drain region having a greatest width at an upper portion that is adjacent the upper surface of the substrate and a smallest width at a deepest portion of the drain region, where the deepest portion of the drain region includes the phosphorous and none of the arsenic, the upper portion of the drain region includes a combination of the phosphorous and the arsenic, and the deepest portion of the drain region has a smaller width than the upper portion of the drain region.
15. The non-volatile memory device of claim 9 , where the source region has a greatest width adjacent the upper surface of the substrate and a smallest width at the deepest location with respect to the upper surface of the substrate,
where the drain region has a greatest width adjacent the upper surface of the substrate and a smallest width at the deepest location with respect to the upper surface of the substrate, and
where deeper portions of the source and drain regions include the phosphorous and none of the arsenic, and upper portions of the source and drain regions include a combination of phosphorous and arsenic.
16. The memory device of claim 1 , where the charge storage element is programmed to concurrently store two separate bits of data.
17. The method of claim 6 , further comprising:
programming the charge storage element to concurrently store two bits of data.
18. The non-volatile memory device of claim 9 , where the charge storage element is programmed to concurrently store two bits of data.