Three-dimensional memory devices with architecture of increased number of bit lines
Embodiments of a three-dimensional (3D) memory device and fabrication method thereof are disclosed. The 3D memory device has an architecture with an increased number of bit lines. In an example, a stack structure is formed above a substrate. A plurality of memory strings each extending vertically through a memory region of the stack structure are formed. A plurality of bit lines are formed over the plurality of memory strings, such that at least one of the plurality of bit lines is electrically connected to a single one of the plurality of memory strings.
1. A method for forming a three-dimensional (3D) memory device, comprising:
forming a stack structure;
forming a plurality of memory strings each extending vertically through a memory region of the stack structure; and
forming a plurality of bit lines over the plurality of memory strings, such that at least one of the plurality of bit lines is electrically connected to a single one of the plurality of memory strings, wherein the plurality of memory strings are arranged in an array extending along a first lateral direction and a second lateral direction in the memory region, the first lateral direction being perpendicular to the second lateral direction, wherein the plurality of bit lines are arranged along the first lateral direction and extend along the second lateral direction, being parallel with one another, and in a plan view, a number of bit lines arranged in a channel pitch along the first lateral direction is at least six.
2. The method of claim 1 , wherein
forming the stack structure comprising forming a dielectric stack comprising stacked dielectric layer pairs; and
the method further comprises after forming the plurality of memory strings, forming a memory stack from the dielectric stack, such that the plurality of memory strings each extends vertically through the memory region of the memory stack.
3. The method of claim 2 , wherein
the memory stack comprises a plurality of interleaved conductive layers and insulating layers extending laterally and intersecting with the plurality of memory strings;
in the plan view, no cut structure overlaps with the plurality of memory strings in the memory region, the memory region being a finger; and
a first conductor layer extends continuously along a direction it extends in the memory region.
4. The method of claim 1 , wherein each one of the plurality of memory strings is electrically connected to a single different one of the plurality of bit lines.
5. The method of claim 1 , further comprising forming at least one slit structure extending laterally along a boundary of the memory region.
6. The method of claim 5 , wherein in the plan view, a number of bit lines arranged in a channel pitch along the first lateral direction is equal to a number of memory strings electrically connected to the bit lines along the second lateral direction.
7. The method of claim 5 , wherein
the array is arranged between two slit structures each laterally extending along the first lateral direction; and
in the plan view, the number of bit lines arranged in the channel pitch is equal to the number of memory strings in the channel pitch and between the two slit structures.
8. The method of claim 7 , wherein in the plan view, the bit lines in the channel pitch are evenly spaced, a bit line pitch along the first lateral direction being nominally equal to 1/N of the channel pitch, N being equal to the number of bit lines in the channel pitch.
9. The method of claim 5 , wherein the array comprises at least six string rows along the second lateral direction.
10. The method of claim 9 , wherein N is a positive even integer.
11. The method of claim 1 , wherein forming the plurality of memory strings comprising, for each of the memory strings, forming a channel structure and a drain over the channel structure, the drain being electrically connected to a respective bit line.
12. The method of claim 1 , further comprising forming a plurality of peripheral devices electrically connected to the plurality of memory strings.