Methods of fabricating three-dimensional nonvolatile memory devices using expansions
Provided are three-dimensional nonvolatile memory devices and methods of fabricating the same. The memory devices include semiconductor pillars penetrating interlayer insulating layers and conductive layers alternately stacked on a substrate and electrically connected to the substrate and floating gates selectively interposed between the semiconductor pillars and the conductive layers. The floating gates are formed in recesses in the conductive layers.
1. A method of fabricating a three-dimensional nonvolatile memory device, the method comprising:
forming openings penetrating interlayer insulating layers and conductive layers stacked alternately on a substrate;
forming expansions having a diameter wider than that of the openings penetrating the interlayer insulating layers by selectively recessing sidewalls of the conductive layers exposed by the openings;
forming first insulating layers on surfaces of the conductive layers exposed by the expansions;
forming floating gates disposed in the expansions interposing the first insulating layers;
forming second insulating layers on surfaces of the floating gates adjacent to the openings; and
forming semiconductor pillars filling the openings.
2. The method of claim 1 , wherein the forming of the expansions includes: isotropically etching the conductive layers so as to selectively etch the conductive layers more than the substrate and the interlayer insulating layers, and
the forming of the floating gates includes: forming buried conductive layers filling the openings and the expansions; and anisotropically etching the buried conductive layers to expose an upper surface of the substrate.
3. The method of claim 1 , wherein the forming of the first insulating layers and the second insulating layers includes: performing an oxidation process or deposition process.
4. The method of claim 1 , further comprising: forming sequentially stacked lower interlayer insulating layers and lower conductive layers including lower openings provided with sidewalls to be connected successively to the openings on the substrate, before forming the openings.
5. The method of claim 1 , further comprising: isolating the interlayer insulating layers and the conductive layers from each other between the semiconductor pillars; and
forming silicide layers on surfaces of the isolated conductive layers.
6. A method of fabricating a three-dimensional nonvolatile memory device comprising:
forming openings penetrating interlayer insulating layers and conductive layers stacked alternately on a substrate; then
recessing sidewalls of the conductive layers that are exposed by the openings relative to sidewalls of the interlayer insulating layers that are exposed by the openings to define expansions between portions of adjacent insulating layers that are exposed by the recessing of the sidewalls of the conductive layers; then
forming floating gates in the expansions; and then
forming semiconductor pillars in the openings to extend on the floating gates and on the sidewalls of the interlayer insulating layers.
7. The method of claim 6 wherein the following is performed between the recessing sidewalls and the forming floating gates:
forming an insulating layer on the sidewalls of the conductive layers.
8. The method of claim 7 wherein the following is performed between the forming floating gates and the forming semiconductor pillars:
forming an insulating layer on the floating gates, adjacent the openings.
9. The method of claim 6 wherein the following is performed between the forming floating gates and the forming semiconductor pillars:
forming an insulating layer on the floating gates, adjacent the openings.
10. The method of claim 6 wherein recessing sidewalls comprises selectively etching the sidewalls of the conductive layers that are exposed by the openings relative to sidewalls of the interlayer insulating layers that are exposed by the openings.
11. The method of claim 6 wherein forming floating gates in the expansions comprises:
forming a conductive layer in the openings and in the expansions; and
removing the conductive layer from the openings while allowing the conductive layer to remain in the expansions.
12. The method of claim 6 wherein forming openings is preceded by:
sequentially stacking lower insulating layers and lower conductive layers upon one another on the substrate; and
forming lower openings penetrating the lower insulating layers and the lower conductive layers; and
wherein forming openings comprises forming openings penetrating interlayer insulating layers and conductive layers stacked alternately on a substrate and aligned to the lower openings.
13. The method of claim 6 further comprising:
forming a silicide layer on sidewalls of the floating gates opposite the semiconductor pillars.
14. The method of claim 13 wherein forming a silicide layer is preceded by forming a conductive layer on the sidewalls of the floating gates opposite the semiconductor pillars.
15. The method of claim 6 wherein the expansions are ring-shaped expansions surrounding the openings.