Methods used in forming a memory array comprising strings of memory cells comprising forming undoped semiconductive material into a void-space
A memory array comprising strings of memory cells comprises conductor tier comprising conductor material. Laterally-spaced memory blocks individually comprising a vertical stack comprises alternating insulative tiers and conductive tiers. Channel-material strings of memory cells extend through the insulative tiers and the conductive tiers. Conducting material of a lower of the conductive tiers directly electrically couples together the channel material of individual of the channel-material strings and the conductor material of the conductor tier. The conducting material in the lower conductive tier comprises upper conductively-doped semiconductive material, lower conductively-doped semiconductive material, and intermediate material vertically there-between. 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 laterally-spaced memory-block regions individually comprising a vertical stack comprising alternating first tiers and second tiers directly above the conductor tier, channel-material strings extending through the first tiers and the second tiers, material of the first tiers being of different composition from material of the second tiers;
forming conducting material in a lowest of the first tiers that directly electrically couples together a channel material of individual of the channel-material strings and the conductor material of the conductor tier, the forming of the conducting material comprising:
forming a first undoped semiconductive material in the lowest first tier directly against a sidewall of the channel material of the individual channel-material strings, the first undoped semiconductive material comprising an upper portion and a lower portion having a void-space vertically there-between, the first undoped semiconductive material having total concentration of all conductivity-modifying dopant therein of 0 atomic percent to less than 0.01 atomic percent;
forming a conductively-doped semiconductive material in the void-space directly against the first undoped semiconductive material, the conductively-doped semiconductive material comprising an upper portion and a lower portion having a remaining portion of the void-space vertically there-between, the conductively-doped semiconductive material having total concentration of all conductivity-modifying dopant therein of 0.01 atomic percent to 30 atomic percent; and
forming a second undoped semiconductive material into and to fill remaining volume of the remaining portion of the void-space and directly against the conductively-doped semiconductive material, the second undoped semiconductive material having total concentration of all conductivity-modifying dopant therein of 0 atomic percent to less than 0.01 atomic percent.
2 . The method of claim 1 wherein the upper and lower portions of the first undoped semiconductive material are each thinner than the second undoped semiconductive material.
3 . The method of claim 1 wherein the upper and lower portions of the first undoped semiconductive material are each thinner than the upper and lower portions of the conductively-doped semiconductive material.
4 . The method of claim 1 wherein the second undoped semiconductive material is thinner than each of the upper and lower portions of the conductively-doped semiconductive material.
5 . The method of claim 4 wherein the upper and lower portions of the first undoped semiconductive material are each thinner than the second undoped semiconductive material.
6 . The method of claim 1 comprising annealing the conductively-doped semiconductive material to cause dopant therein to out-diffuse into the first undoped semiconductive material to dope it and render it conductive.
7 . The method of claim 1 comprising annealing the conductively-doped semiconductive material to cause dopant therein to out-diffuse into the second undoped semiconductive material to dope it and render it conductive.
8 . The method of claim 1 wherein the first undoped semiconductive material and the second undoped semiconductive material are of the same composition relative one another.
9 . The method of claim 1 wherein,
the total concentration in each of the first and second undoped semiconductive materials is greater than 0 atomic percent; and
the dopant in the first undoped semiconductive material, the dopant in the conductively-doped semiconductive material, and in the second undoped semiconductive material are the same composition dopant.
10 . The method of claim 1 wherein each of the first undoped semiconductive material, the conductively-doped semiconductive material, and the second undoped semiconductive material comprises polysilicon.
11 . The method of claim 10 wherein,
the total concentration in each of the first and second undoped semiconductive materials is greater than 0 atomic percent; and
the dopant in the first undoped semiconductive material, the dopant in the conductively-doped semiconductive material, and in the second undoped semiconductive material are the same composition dopant.