Memory array and method used in forming a memory array comprising strings of memory cells
A memory array comprises laterally-spaced memory blocks individually comprising a vertical stack comprising alternating insulative tiers and conductive tiers. Channel-material strings of memory cells extend through the insulative tiers and the conductive tiers. Dummy pillars extend through the insulative tiers and the conductive tiers. A lowest of the conductive tiers comprises conducting material and dummy-region material that is aside and of different composition from that of the conducting material. The channel-material strings extend through the conducting material of the lowest conductive tier. The dummy pillars extend through the dummy-region material of the lowest conductive tier. Other embodiments, including method, are disclosed.
1. A method used in forming a memory array comprising strings of memory cells, comprising:
forming a conductor tier comprising conductor material on a substrate;
forming a lower portion of a stack that will comprise vertically-alternating first tiers and second tiers above the conductor tier, the stack comprising laterally-spaced memory-block regions, material of the first tiers being of different composition from material of the second tiers, a lowest of the first tiers comprising:
sacrificial material; and
dummy-region material that is aside and of different composition from that of the sacrificial material;
forming the vertically-alternating first tiers and second tiers of an upper portion of the stack above the lower portion;
forming operative channel-material strings that extend through the first tiers and the second tiers in the upper portion and to the sacrificial material in the lowest first tier;
forming dummy pillars that extend through the first tiers and the second tiers in the upper portion and to the dummy-region material in the lowest first tier;
forming horizontally-elongated trenches into the stack that are individually between immediately-laterally-adjacent of the memory-block regions and extend to the sacrificial material in the lowest first tier;
isotropically etching the sacrificial material from the lowest first tier through the trenches selectively relative to the dummy-region material; and
after the etching, forming conductive material in the lowest first tier aside the dummy-region material, the conductive material directly electrically coupling together the channel material of individual of the operative channel-material strings and the conductor material of the conductor tier.
2. The method of claim 1 wherein all of the dummy-region material that is in the lowest first tier is in the memory-block regions in a finished circuitry construction.
3. The method of claim 1 wherein the dummy-region material that is in the lowest first tier comprises a line of the dummy-region material in and running centrally-longitudinally-along individual of the memory-block regions, the line being spaced laterally from lateral sides of the individual memory-block regions.
4. The method of claim 1 wherein the dummy-region material that is in the lowest first tier is in and extends laterally across all of individual of the memory-block regions aside a stair-step region of the individual memory-block regions.
5. The method of claim 1 wherein,
the dummy-region material that is in the lowest first tier comprises a line of the dummy-region material in and running centrally-longitudinally-along individual of the memory-block regions, the line being spaced laterally from lateral sides of the individual memory-block regions; and
the dummy-region material that is in the lowest first tier is in and extends laterally across all of individual of the memory-block regions aside a stair-step region of the individual memory-block regions.
6. The method of claim 1 comprising forming the operative channel-material strings and the dummy pillars to extend through the lowest first tier in the lower portion.
7. The method of claim 6 wherein the operative channel-material strings and the dummy pillars extend into the conductor material of the conductor tier.
8. The method of claim 1 comprising forming the operative channel-material strings and the dummy pillars at the same time and of the same composition relative one another.
9. The method of claim 1 wherein the sacrificial and dummy-region materials comprise polysilicon and the isotropically etching comprises use of tetramethyl ammonium hydroxide.
10. The method of claim 1 wherein the dummy-region material is formed by a process comprising:
forming a blanket layer of the sacrificial material in the lowest first tier; and
ion implanting regions of the blanket layer of the sacrificial material to form said dummy-region material.
11. The method of claim 10 wherein the ion implanting is with one of more of C, N, B, Ga, As, Sb, Bi, Li, Al, In, a Group 18 element, or a metal material.
12. The method of claim 10 wherein,
the sacrificial material comprises polysilicon or silicon nitride;
the ion implanting is with one of more of C, N, B, Ga, As, Sb, Bi, Li, Al, In, a Group 18 element, or a metal material; and
the isotropically etching comprises use of tetramethyl ammonium hydroxide or phosphoric acid.
13. The method of claim 1 wherein the dummy-region material is formed by a process comprising:
forming a blanket layer of the sacrificial material in the lowest first tier;
subtractively patterning the blanket layer of the sacrificial material to form void space therein; and
forming the dummy-region material in the void space.
14. The method of claim 1 wherein the dummy-region material is formed by a process comprising:
forming a blanket layer of the dummy-region material in the lowest first tier;
subtractively patterning the blanket layer of the dummy-region material; and
forming the sacrificial material aside the dummy-region material.
15. The method of claim 1 wherein the dummy-region material is insulative.
16. The method of claim 1 wherein the dummy-region material is conductive.
17. The method of claim 1 wherein the dummy-region material is semiconductive.
18. The method of claim 1 wherein the isotropically etching of the sacrificial material from the lowest first tier through the trenches is at a selectivity relative to the dummy-region material of at least 5:1.