Three-dimensional memory device containing a vertical semiconductor channel containing a connection strap and method of making the same

1. A three-dimensional memory device, comprising:

an alternating stack of insulating layers and electrically conductive layers located over a substrate;

memory openings vertically extending through the alternating stack; and

memory opening fill structures located within a respective one of the memory openings, wherein each of the memory opening fill structures comprises:

a memory film contacting a sidewall of a respective memory opening and including an opening at a bottom portion thereof;

a vertical semiconductor channel contacting an inner sidewall of the memory film and overlying the opening in the memory film;

a dielectric core contacting an inner sidewall of the vertical semiconductor channel; and

a connection strap comprising a semiconductor material, extending through the opening in the memory film, and contacting a bottom surface of the vertical semiconductor channel and a top surface of a semiconductor material that underlies the respective memory opening,

wherein:

the connection strap comprises a single crystalline strap semiconductor material;

the vertical semiconductor channel comprises a polycrystalline semiconductor material; and

the dielectric core also contacts the single crystalline strap semiconductor material of the connection strap.

2. The three-dimensional memory device of claim 1 , wherein the connection strap comprises:

a lower portion vertically extending below a horizontal plane including a bottommost surface of the memory film; and

an upper portion vertically extending above a horizontal plane including an upper edge of the opening through the memory film.

3. The three-dimensional memory device of claim 2 , wherein:

a first region of the upper portion of the connection strap contacts a bottom surface of the dielectric core; and

a second region of the upper portion of the connection strap extends around and contacts a sidewall of a lower part of the dielectric core.

4. The three-dimensional memory device of claim 1 , wherein:

the substrate comprises a single crystalline substrate semiconductor material; and

the connection strap is in epitaxial alignment with the single crystalline substrate semiconductor material.

5. The three-dimensional memory device of claim 4 , wherein the semiconductor material that underlies the respective memory opening comprises an epitaxial pedestal structure in epitaxial alignment with the underlying single crystalline substrate semiconductor material and with the overlying connection strap.

6. The three-dimensional memory device of claim 5 , wherein:

the connection strap comprises single crystalline silicon doped with at least one of boron or carbon; and

the vertical semiconductor channel comprises boron doped polysilicon;

the connection strap comprises single crystalline silicon with a same doping level as the epitaxial pedestal structure; and

the vertical semiconductor channel comprises the same doping level as the epitaxial pedestal structure and the connection strap.

7. The three-dimensional memory device of claim 4 , wherein:

the semiconductor material that underlies the respective memory opening comprises the single crystalline substrate semiconductor material; and

the connection strap is in direct contact with, and in epitaxial alignment with, the single crystalline substrate semiconductor material.

8. The three-dimensional memory device of claim 1 , wherein the vertical semiconductor channels and an upper portion of each connection strap have a same material composition.

9. The three-dimensional memory device of claim 1 , wherein each of the memory films comprises a layer stack that includes:

a charge storage layer; and

a tunneling dielectric layer contacting an inner sidewall of the charge storage layer.

10. The three-dimensional memory device of claim 9 , wherein the tunneling dielectric layer contacts an outer sidewall of a respective one of the vertical semiconductor channels, and at least one outer sidewall of a respective one of the connection straps.

11. The three-dimensional memory device of claim 1 , wherein each of the memory opening fill structures comprises a drain region contacting a top end of a respective vertical semiconductor channel.

12. The three-dimensional memory device of claim 1 , wherein each vertically neighboring pair of an insulating layer and an electrically conductive layer is spaced from each other by a backside blocking dielectric layer that contacts outer sidewalls of the memory opening fill structures.

13. The three-dimensional memory device of claim 1 , wherein:

the alternating stacks comprise stepped surfaces in a staircase region, wherein each electrically conductive layer other than a topmost one of the electrically conductive layers laterally extends farther than an overlying electrically conductive layer;

layer contact via structures contact a top surface of a respective one of the electrically conductive layers in the staircase region;

a retro-stepped dielectric material portion overlies the stepped surfaces; and

support pillar structures extend through the retro-stepped dielectric material portion and the stepped surfaces in the staircase region.