Semiconductor structure for three-dimensional memory device and manufacturing method thereof
A semiconductor structure for three-dimensional memory device and a manufacturing method thereof are provided. In the manufacturing method, clean plasma is used to clean the impurity doped regions, formed by slit etching, in the surface layer of the substrate to decrease the contact resistance between substrate and conductive plugs formed in the slits. The bottom part of the conductive plugs each has a reduced neck structure and an enlarged bottom structure.
1. A semiconductor structure for a three-dimensional memory device, comprising:
a stacked structure disposed on a substrate, wherein the stacked structure comprises a plurality of insulation layers and a plurality of control gate layers which are alternatively stacked, and the stacked structure has a plurality of channel openings vertically penetrating the stacked structure, and a plurality of slits between the adjacent two rows of the channel openings and vertically extending through the stacked structure;
a plurality of channel pillars respectively located in the plurality of the channel openings and contacting the substrate, wherein the plurality of channel pillars each sequentially comprises a blocking insulation layer, a charge trapping layer, a tunneling insulation layer, a channel layer, and a core layer, from outside to inside;
a plurality of isolating insulation layers respectively disposed on the inner walls of the plurality of the slits; and
a plurality of conductive plugs respectively located between the plurality of isolating insulation layers, wherein a bottom part of each of the conductive plugs has a reduced neck structure and an enlarged bottom structure that extends into the substrate.
2. The semiconductor structure of claim 1 , wherein the slit has an aspect ratio of 30-60.
3. The semiconductor structure of claim 1 , wherein the slit has a depth of 3 to 12 μm.
4. The semiconductor structure of claim 1 , wherein the enlarged bottom structure of the conductive plug extends into the substrate to a depth of 30-800 Å.
5. The semiconductor structure of claim 1 , further comprising metal silicide disposed between the conductive plugs and the substrate.
6. The semiconductor structure of claim 1 , further comprising a dielectric layer having a high dielectric constant and a metal barrier layer sequentially surrounding the insulation layer of the stacked structure.
7. A method of manufacturing a semiconductor structure for a three-dimensional memory device, comprising:
forming a stacked structure on a substrate, wherein the stacked structure comprises a plurality of insulation layers and a plurality of sacrificial layers which are alternatively stacked;
forming a plurality of channel openings vertically penetrating the stacked structure and exposing the substrate;
sequentially forming a blocking insulation layer, a charge trapping layer, a tunneling insulation layer, a channel layer, and a core layer, from outside to inside, in each of the plurality of the channel openings;
forming a plurality of slits vertically extending through the stacked structure and exposing the substrate, wherein the plurality of the slits are located between adjacent two columns of the channel openings, and each of the exposed substrate has an impurity doped region in the surface layer of the exposed substrate;
removing the plurality of sacrificial layers in the stacked structure;
forming a plurality of control gate layers between adjacent two of the insulation layers;
forming a plurality of isolating insulation layers on the inner surface of the plurality of the slits;
etching each of the isolating insulation layers on the surface of the substrate to form slit openings to expose the substrate;
removing the impurity doped region of the surface layer of the substrate to form a bottom opening; and
forming a plurality of conductive plugs between the isolating insulation layers in each of the slits, wherein the conductive plugs each has a reduced neck structure located in the slit opening and an enlarged bottom structure located in the bottom opening.
8. The method of claim 7 , wherein the removal of the impurity doped region comprises dry etching using a clean plasma.
9. The method of claim 8 , wherein a biasing power of the accelerated electric field for the clean plasma is at most 100 W.
10. The method of claim 8 , wherein when the impurities in the impurity doped region contains carbon and fluorine, the gas source of the clean plasma comprises a halogen-containing gas and a hydrogen-containing gas.
11. The method of claim 10 , wherein
the halogen-containing gas comprises Cl 2 , Br 2 , or HBr; and
the hydrogen-containing gas comprises H 2 .
12. The method of claim 10 , wherein the gas source for cleaning the plasma further comprises an inert gas.
13. The method of claim 12 , wherein the inert gas comprises N 2 , He or Ar.
14. The method of claim 7 , wherein the forming the plurality of conductive plugs further comprises forming a metal silicide on the surface of the substrate.
15. The method of claim 7 , wherein the sacrificial layer is removed by isotropic etching.
16. The method of claim 7 , further comprising forming a dielectric layer to surround the exposed insulation layer between removing the sacrificial layers and forming the conductive plugs.
17. The method of claim 16 , further comprising forming a metal barrier layer on the dielectric layer between forming the dielectric layer and forming the conductive plugs.