Three-dimensional memory device with backside support pillar structures and methods of forming the same
At least one vertically alternating sequence of continuous insulating layers and continuous sacrificial material layers is formed over a substrate. Rows of backside support pillar structures are formed through the at least one vertically alternating sequence. Memory stack structures are formed through the at least one vertically alternating sequence. A two-dimensional array of discrete backside trenches is formed through the at least one vertically alternating sequence. Contiguous combinations of a subset of the backside trenches and a subset of the backside support pillar structures divide the at least one vertically alternating sequence into alternating stacks of insulating layers and sacrificial material layers. The sacrificial material layers are replaced with electrically conductive layers while the backside support pillar structures provide structural support to the insulating layers.
1. A method of forming a semiconductor structure, comprising:
forming at least one vertically alternating sequence of continuous insulating layers and continuous sacrificial material layers over a substrate;
forming rows of backside support pillar structures through the at least one vertically alternating sequence;
forming memory stack structures through the at least one vertically alternating sequence, wherein each of the memory stack structures comprises a respective vertical semiconductor channel and a respective vertical stack of memory elements;
forming a two-dimensional array of discrete backside trenches through the at least one vertically alternating sequence such that contiguous combinations of the discrete backside trenches and the backside support pillar structures are formed, wherein the contiguous combinations divide the at least one vertically alternating sequence into alternating stacks of insulating layers and sacrificial material layers, and wherein each of the insulating layers comprises a patterned portion of a respective one of the continuous insulating layers and each of the sacrificial material layers comprises a patterned portion of a respective one of the continuous sacrificial material layers; and
replacing the sacrificial material layers with electrically conductive layers by providing an etchant that etches the sacrificial material layers into the backside trenches and by providing a reactant that deposits the electrically conductive layers into the backside trenches while the backside support pillar structures provide structural support to the insulating layers,
wherein each of the contiguous combinations comprises a respective discrete backside trench and a respective set of two backside support pillar structures each having a respective set of at least one sidewall surface segment that is physically exposed to the respective discrete backside trench upon formation of the discrete backside trenches and prior to etching the sacrificial material layers.
2. The method of claim 1 , wherein the two-dimensional array of discrete backside trenches is formed by anisotropically etching portions of the at least one vertically alternating sequence and peripheral portions of the backside support pillar structures, wherein sidewalls of the backside support pillar structures are physically exposed to the backside trenches.
3. The method of claim 1 , wherein:
each row of the backside support pillar structures comprises a subset of the backside support pillar structures that are arranged along a first horizontal direction; and
the two-dimensional array of discrete backside trenches comprise rows of discrete backside trenches that are arranged along the first horizontal direction.
4. The method of claim 3 , wherein:
each of the discrete backside trenches comprises a respective pair of straight sidewalls that laterally extend along the first horizontal direction; and
each contiguous combination of a respective subset of the backside trenches and a respective subset of the backside support pillar structures laterally extends along the first horizontal direction.
5. The method of claim 1 , further comprising forming arrays of support pillar structures between the rows of backside support pillar structures and through the at least one vertically alternating sequence concurrently with formation of the backside support pillar structures.
6. The method of claim 1 , further comprising forming a contact-level dielectric layer over the at least one vertically alternating sequence and over the backside support pillar structures, wherein the two-dimensional periodic array of discrete backside trenches is formed through the contact-level dielectric layer and through the at least one vertically alternating sequence.
7. The method of claim 6 , further comprising forming backside dielectric isolation walls in the backside trenches by depositing a dielectric fill material in the backside trenches, wherein top surfaces of the backside dielectric isolation walls are formed within a horizontal plane including a top surface of the contact-level dielectric layer.
8. The method of claim 1 , wherein, for each contiguous combination, the respective set of at least one sidewall surface segment comprises a plurality of sidewall surface segments facing different horizontal directions that are not parallel or perpendicular to each other.
9. The method of claim 1 , wherein:
each continuous combination laterally extends along a first horizontal direction; and
for each contiguous combination, the respective set of at least one sidewall surface segment comprises a respective first sidewall surface segment that is parallel to the first horizontal direction.
10. The method of claim 9 , wherein, for each contiguous combination, the respective set of at least one sidewall surface segment comprises a respective second surface segment that is perpendicular to the first horizontal direction.
11. The method of claim 9 , wherein, for each contiguous combination, the respective set of at least one sidewall surface segment comprises two second surface segments of a backside support pillar structure within the respective set of two backside support pillar structures, the two second surface segments being perpendicular to the first horizontal direction.
12. The method of claim 1 , wherein sidewalls of the discrete backside trenches comprise surface segments of the backside support pillar structures.
13. The method of claim 1 , wherein one of the backside support pillar structures is patterned during formation of the discrete backside trenches such that sidewalls of said one of the backside support pillar structures comprise first sidewalls that are physically exposed to a first one of the discrete backside trenches and second sidewalls that are physically exposed to a second one of the discrete backside trenches.
14. The method of claim 13 , wherein a lateral spacing between the first one of the discrete backside trenches and the second one of the discrete backside trenches is less than a maximum lateral dimension of said one of the backside support pillar structures after formation of the discrete backside trenches along a separation direction between the first one of the discrete backside trenches and the second one of the discrete backside trenches.
15. The method of claim 13 , wherein a lateral dimension of said one of the backside support pillar structures along a horizontal direction that is perpendicular to a lateral separation direction between the first one of the discrete backside trenches and the second one of the discrete backside trenches is greater than a width of the first one of the discrete backside trenches along a horizontal direction that is perpendicular to the lateral separation direction between the first one of the discrete backside trenches and the second one of the discrete backside trenches.
16. The method of claim 1 , wherein sidewalls of one of the discrete backside trenches comprise:
first sidewall segments that are physically exposed surface segments a first backside support pillar structure of the backside support pillar structures; and
second sidewall segments that are physically exposed surface segments a second backside support pillar structure of the backside support pillar structures.
17. The method of claim 16 , wherein:
the discrete backside trenches laterally extend along a first horizontal direction; and
the physically exposed surface segments of the first backside support pillar structure comprise a sidewall surface segment that is parallel to the first horizontal direction and another sidewall surface segment that is perpendicular to the first horizontal direction.
18. The method of claim 16 , wherein:
the discrete backside trenches laterally extend along a first horizontal direction; and
the first backside support pillar structure and the second backside support pillar structure are laterally spaced from each other along the first horizontal direction.
19. The method of claim 18 , wherein the sidewalls of said one of the discrete backside trenches comprise:
third sidewall segments that are physically exposed surface segments a third backside support pillar structure of the backside support pillar structures; and
fourth sidewall segments that are physically exposed surface segments a fourth backside support pillar structure of the backside support pillar structures.
20. The method of claim 19 , wherein:
the third backside support pillar structure is laterally spaced from the first backside support pillar structure along a second horizontal direction that is perpendicular to the first horizontal direction; and
the fourth backside support pillar structure is laterally spaced from the second backside support pillar structure along the second horizontal direction.