Three-dimensional memory devices with improved back-side channel structures
Three-dimensional (3D) memory devices and methods for forming the same are disclosed. In certain aspects, a 3D memory device includes a stack structure including interleaved conductive layers and stack dielectric layers, a channel structure extending through the stack structure, and a doped semiconductor layer. The channel structure includes a memory film and a semiconductor channel. The semiconductor channel includes a doped portion and an undoped portion. A part of the doped portion of the semiconductor channel extends beyond the stack structure in a first direction. A part of the doped semiconductor layer is in contact with a sidewall of the part of the doped portion of the semiconductor channel that extends beyond the stack structure.
1. A three-dimensional (3D) memory device, comprising:
a stack structure comprising interleaved conductive layers and dielectric layers;
a plurality of channel structures extending through the stack structure, each channel structure comprising a memory film and a semiconductor channel, wherein the semiconductor channel comprises a doped portion, and a part of the doped portion of the semiconductor channel extends beyond the stack structure in a first direction;
a filling layer in contact with a top dielectric layer of the stack structure and having a first thickness; and
a doped semiconductor layer comprising:
a lateral portion of the doped semiconductor layer covering the filling layer, and
a plurality of protruding portions of the doped semiconductor layer each extending vertically from the lateral portion of the doped semiconductor layer, and encasing an end of the part of the doped portion of the semiconductor channel of a corresponding channel structure
an interlayer dielectric layer covering the doped semiconductor layer; and
a redistribution layer comprising:
a lateral portion of the redistribution layer covering the interlayer dielectric layer,
a first protruding portion of the redistribution layer extending vertically from a first side of the lateral portion of the redistribution layer and in contact with the doped semiconductor layer; and
a first recess on a second side of the lateral portion of the redistribution layer and aligned with the first protruding portion of the redistribution layer in a vertical direction.
2. The 3D memory device of claim 1 , wherein a doping concentration of the doped portion of the semiconductor channel and a doping concentration of the doped semiconductor layer each is between 10 19 cm −3 and 10 21 cm −3 .
3. The 3D memory device of claim 1 , wherein the doped portion of the semiconductor channel and the doped semiconductor layer each comprises N-type doped polysilicon.
4. The 3D memory device of claim 1 , wherein the doped portion of the semiconductor channel extends beyond one of the conductive layers in a second direction opposite to the first direction.
5. The 3D memory device of claim 4 , wherein the one of the conductive layers comprises a source select gate line.
6. The 3D memory device of claim 1 , wherein one end of the memory film is flush with or exceeds a corresponding surface of the stack structure.
7. The 3D memory device of claim 1 , wherein the 3D memory device is configured to generate gate-induced-drain-leakage (GIDL)-assisted body bias when performing an erase operation.
8. The 3D memory device of claim 1 , further comprising:
an insulating structure extending laterally to separate the stack structure and vertically through the stack structure and stopping at the filling layer.
9. The 3D memory device of claim 1 , wherein the redistribution layer further comprises:
a second protruding portion of the redistribution layer each extending vertically from the lateral portion of the redistribution layer through the interlayer dielectric layer and the doped semiconductor layer, and in contact with a peripheral contact extending vertically beside of the stack structure;
a second recess on the second side of the lateral portion of the redistribution layer and aligned with the second protruding portion of the redistribution layer in the vertical direction; and
a first height of the first protruding portion of the redistribution layer is less than a second height of the second protruding portion of the redistribution layer in the vertical direction.
10. The 3D memory device of claim 9 , wherein a first semiconductor structure comprising a peripheral circuit is bonded with a second semiconductor structure comprising the stack structure, the peripheral circuit being coupled with the channel structures through the peripheral contact.
11. The 3D memory device of claim 9 , wherein the doped portion of the semiconductor channel extends beyond one of the conductive layers in a second direction opposite to the first direction.
12. The 3D memory device of claim 11 , wherein the one of the conductive layers comprises a source select gate line.
13. A three-dimensional (3D) memory device, comprising:
a stack structure comprising interleaved conductive layers and dielectric layers;
a filling layer in contact with a top dielectric layer of the stack structure;
a doped semiconductor layer comprising:
a lateral portion of the doped semiconductor layer covering the filling layer, and
a plurality of protruding portions of the doped semiconductor layer each extending vertically from the lateral portion of the doped semiconductor layer
an interlayer dielectric layer covering a second side of the doped semiconductor layer; and
a redistribution layer comprising:
a lateral portion of the redistribution layer covering the interlayer dielectric layer,
a first protruding portion of the redistribution layer extending vertically from the lateral portion of the redistribution layer and in contact with the second side of the doped semiconductor layer,
a second protruding portion of the redistribution layer extending vertically from the lateral portion of the redistribution layer through the interlayer dielectric layer and the doped semiconductor layer, isolated from the doped semiconductor layer and in contact with a peripheral contact extending vertically beside of the stack structure,
wherein a first height of the first protruding portion of the redistribution layer is less than a second height of the second protruding portion of the redistribution layer in a vertical direction; and
a plurality of channel structures extending through the stack structure to the doped semiconductor layer, each channel structure comprising a memory film and a semiconductor channel,
wherein the semiconductor channel comprises a doped portion, and the doped portion of the semiconductor channel is between the doped semiconductor layer and one of the conductive layers that is closest to the doped semiconductor layer, and
wherein each protruding portion of the doped semiconductor layer encases an end of the doped portion of the semiconductor channel of a corresponding one of the plurality of channel structures.
14. The 3D memory device of claim 13 , further comprising:
an insulating structure extending laterally to separate the stack structure and vertically through the stack structure and stopping at the filling layer.
15. The 3D memory device of claim 13 , wherein a doping concentration of the doped portion of the semiconductor channel and a doping concentration of the doped semiconductor layer each is between 10 19 cm −3 and 10 21 cm −3.
16. The 3D memory device of claim 13 , wherein the doped portion of the semiconductor channel and the doped semiconductor layer each comprises N-type doped polysilicon.
17. The 3D memory device of claim 13 , wherein one end of the memory film is flush with or exceeds a corresponding surface of the stack structure.
18. The 3D memory device of claim 13 , wherein the 3D memory device is configured to generate gate-induced-drain-leakage (GIDL)-assisted body bias when performing an erase operation.
19. The 3D memory device of claim 13 , wherein the redistribution layer further comprises:
a first recess and a second recess on a side of the lateral portion of the redistribution layer opposite to the first protruding portion and the second protruding portion of the redistribution layer;
the first recess being aligned with the first protruding portion of the redistribution layer in a vertical direction; and
the second recess being aligned with the second protruding portion of the redistribution layer in the vertical direction.
20. The 3D memory device of claim 13 , wherein a first semiconductor structure comprising a peripheral circuit is bonded with a second semiconductor structure comprising the stack structure, the peripheral circuit being coupled with the channel structures through the peripheral contact and
in contact with a peripheral contact extending vertically beside of the stack structure.