Reducing leakage currents in memories with phase-change material
View Patent ↗A memory cell including a phase-change material may have reduced leakage current. The cell may receive signals through a buried wordline in one embodiment. The buried wordline may include a sandwich of a more lightly doped N type region over a more heavily doped N type region over a less heavily doped N type region. As a result of the configuration of the N type regions forming the buried wordline, the leakage current of the buried wordline to the substrate under reverse bias conditions may be significantly reduced.
1. A method comprising:
forming a buried line of a first conductive type in a semiconductor substrate, said buried line including a pair of more lightly doped regions in the substrate around a more heavily doped region, said regions having substantially the same length;
creating a region of a second conductivity type opposite said first conductivity type over said line; and
forming a phase-change material over said region.
2. The method of claim 1 including forming a passage through a dielectric layer.
3. The method of claim 2 including forming a contact layer under said dielectric layer and forming said passage through said dielectric layer to said contact layer.
4. The method of claim 3 including forming the phase-change material in said passage.
5. The method of claim 1 including forming a buried line wherein said lightly doped regions reduce the reverse bias leakage of said line.
6. The method of claim 5 including forming said more lightly doped regions using ion implantation.
7. The method of claim 1 including forming a pair of trenches on either side of said buried line extending past said buried line and said region of a second conductivity type into said substrate under said buried line.
8. The method of claim 1 wherein forming a buried line includes forming a buried wordline.
9. The method of claim 1 including forming said more lightly doped regions of N type material.
10. The method of claim 9 including forming a P type region over said buried line and forming said buried line in a P type substrate.