3D NAND with integral drain-end select gate (SGD)
A 3D NAND storage device includes a plurality of layers containing doped semiconductor material interleaved with a plurality of layers of dielectric material. Each of the pillars forming the 3D NAND storage device includes a plurality of memory cells and a drain-end select gate (SGD). The pillars are separated by a hollow channel in which a plurality of film layers, including at least a lower film layer and an upper film layer have been deposited. The systems and methods described herein remove at least the upper film layer proximate the SGD while maintaining the film layers proximate the memory cells. Such an arrangement beneficially permits tailoring the film layers proximate the SGD prior to depositing the channel film layer in the hollow channel. The systems and methods described herein permit the deposition of a continuous channel film layer proximate both the memory cells and the SGD.
1. A three-dimensional NAND (3D NAND) structure, comprising:
a plurality of memory cells disposed about at least a portion of a length of a hollow channel, the hollow channel having at least an open first end and a closed second end;
a drain-end select gate (SGD) formed about the hollow channel, the SGD extending from a first depth below the open first end of the hollow channel to a second depth measured from the open first end of the hollow channel;
a plurality of film layers that includes at least an upper film layer and a lower film layer disposed across at least a portion of an interior surface of the hollow channel;
wherein to the second depth measured from the first end of the hollow channel, the plurality of film layers comprises the plurality of film layers less the upper film layer; and
wherein beyond the second depth measured from the first end of the hollow channel, the plurality of film layers includes at least the upper film layer and the lower film layer; and
a continuous channel film layer;
wherein the upper film layer, the lower film layer, and the continuous channel film layer extend from the second depth below the open first end of the hollow channel to the second end of the hollow channel and across the closed second end of the hollow channel.
2. The 3D NAND structure of claim 1 , further comprising a continuous channel fill material that extends from the first end of the hollow channel to the second end of the hollow channel.
3. The 3D NAND structure of claim 2 wherein the continuous channel fill material comprises a continuous polysilicon fill material.
4. The 3D NAND structure of claim 1 , the drain-end select gate (SGD) disposed between the first end of the hollow channel and the plurality of memory cells.
5. The 3D NAND structure of claim 1 wherein the continuous channel film layer comprises a continuous channel film layer having a thickness that varies by less than +/−10% of an average thickness of the continuous channel film layer.
6. An electronic device, comprising:
a printed circuit board; and
a three-dimensional NAND (3D NAND) structure operably coupled to the printed circuit board, the 3D NAND including:
a plurality of memory cells disposed about at least a portion of a length of a hollow channel, the hollow channel having at least an open first end and a closed second end;
a drain-end select gate (SGD) formed about the hollow channel, the SGD extending from a first depth below the open first end of the hollow channel to a second depth measured from the open first end of the hollow channel;
a plurality of film layers that includes at least an upper film layer and a lower film layer disposed across at least a portion of an interior surface of the hollow channel;
wherein to the second depth measured from the first end of the hollow channel, the plurality of film layers comprises the plurality of film layers less the upper film layer; and
wherein beyond the second depth measured from the first end of the hollow channel, the plurality of film layers includes at least the upper film layer and the lower film layer; and
a continuous channel film layer;
wherein the upper film layer, the lower film layer, and the continuous channel film layer extend from the second depth below the open first end of the hollow channel to the second end of the hollow channel and across the closed second end of the hollow channel.
7. The electronic device of claim 6 , further comprising a continuous channel fill material that extends from the first end of the hollow channel to the second end of the hollow channel.
8. The electronic device of claim 7 wherein the continuous channel fill material comprises a continuous polysilicon fill material.
9. The electronic device of claim 6 , the SGD disposed between the first end of the hollow channel and the plurality of memory cells.