TECHNIQUES FOR MANUFACTURING SPLIT-CELL 3D-NAND MEMORY DEVICES

1 .- 20 . (canceled)

21 . A method of manufacturing a 3-dimensional NAND (3D-NAND) memory device, the method comprising:

depositing a plurality of alternating first and second layers to form a stack, wherein the first layers comprising a first material and the second layers comprising a second material;

forming a plurality of grooves comprising the first material in the stack, the grooves extending along a wordline direction of the 3D-NAND memory device and dividing at least some of the second layers into strips extending along the wordline direction;

etching a plurality of channel holes in the stack, each channel hole overlapping one of the grooves and being wider than the one of the grooves in a bitline direction orthogonal to the wordline direction; and

depositing a memory layer and a channel layer into the channel holes to form vertical NAND strings.

22 . The method of claim 21 , wherein forming plurality of grooves comprises defining a gap region between two adjacent grooves substantially in alignment along the wordline direction.

23 . The method of claim 22 , wherein the channel holes etched in the stack are not overlapping the gap region.

24 . The method of claim 22 , further comprising:

etching a plurality of separation trenches in the stack, the separation trenches extending along the wordline direction;

selectively removing the second material of the second layers from exposed sidewalls of the second layers in the separation trenches;

depositing gate metal into spaces revealed by the removed second material, wherein the gap region providing a path for removing the second material and depositing the gate metal;

removing materials left in the separation trenches; and

filling the separation trenches with a dielectric material.

25 . The method of claim 21 , further comprising:

forming a staircase region on at least one side of the stack, wherein the plurality of grooves extending into the staircase region.

26 . The method of claim 25 , wherein:

at least one of the grooves only extends partially into the staircase region;

at least one second layer at a bottom of the stack has a first portion and a second portion on opposite sides of at least one of the grooves; and

the first and second portions are connected through remaining portion of the at least one second layer in the staircase region.

27 . The method of claim 21 , wherein:

the stack has a first height; and

at least one of the grooves has a second height less than the first height such that at least one of the second layers at a bottom of the stack not divided by at least one of the grooves.

28 . The method of claim 21 , wherein the channel holes are arranged in a staggered manner.

29 . The method of claim 21 , wherein the memory layer comprises a charge storage layer, a blocking dielectric between a channel hole sidewall and the charge storage layer, and a tunneling dielectric between the charge storage layer and the channel layer.

30 . The method of claim 29 , wherein the charge storage layer comprises a charge trapping layer.

31 . The method of claim 29 , wherein the charge storage layer comprises floating gates.

32 . The method of claim 31 , wherein the channel layer comprises polycrystalline silicon or silicon germanium.

33 .- 35 . (canceled)

36 . A method of manufacturing a U-shape NAND string for a 3-dimensional NAND (3D-NAND) memory device, the method comprising:

providing a substrate having a pipe connection;

depositing a plurality of alternating first and second layers to form a stack, wherein the first layers comprising a first material and the second layers comprising a second material;

forming first and second grooves comprising the first material in the stack, the first and second grooves extending along a wordline direction of the 3D-NAND memory device;

etching first and second channel holes in the stack to partially expose the pipe connection in the substrate, wherein the first channel hole overlapping the first groove and being wider than the first groove in a bitline direction orthogonal to the wordline direction, and wherein the second channel hole overlapping the second groove and being wider than the second groove in the bitline direction; and

depositing a memory layer and a channel layer into the first and second channel holes to form the U-shape NAND string.

37 . The method of claim 36 , further comprising:

etching first, second, and third separation trenches in the stack, the first, second, and third separation trenches extending along the wordline direction, wherein first groove located between the first and second separation trenches, the second separation trench located between the first and second grooves, and the second groove located between the second and third separation trenches; and

filling the first and second separation trenches with a dielectric material.

38 . The method of claim 36 , further comprising:

forming a staircase region on at least one side of the stack, wherein the first and second grooves extending into the staircase region.

39 . The method of claim 38 , wherein:

at least one of the grooves only extends partially into the staircase region;

at least one second layer at a bottom of the stack has a first portion and a second portion on opposite sides of at least one of the grooves; and

the first and second portions are connected through remaining portions of the at least one second layer in the staircase region.

40 . The method of claim 36 , wherein the second material is doped polysilicon.

41 . The method of claim 36 , wherein the first material is silicon oxide.

42 . The method of claim 36 , wherein the memory layer comprises a charge storage layer, a blocking dielectric between the second material and the charge storage layer, and a tunneling dielectric between the charge storage layer and the channel layer.

43 . The method of claim 42 , wherein the charge storage layer comprises a charge trapping layer.

44 . The method of claim 42 , wherein the charge storage layer comprises floating gates.