Memory array comprising strings of memory cells and method used in forming a memory array comprising strings of memory cells

A method used in forming a memory array comprising strings of memory cells, comprising:

• forming a lower stack comprising vertically-alternating lower first tiers and lower second tiers, the lower stack comprising laterally-spaced memory-block regions;
• simultaneously forming (a), (b), and (c), where,
• (a):
• horizontally-elongated lower trenches into the lower stack laterally-between immediately-laterally-adjacent of the memory-block regions;
• (b):
• lower channel openings into the lower stack laterally-between the horizontally-elongated lower trenches;
• and
• (c):
• lower through-array-via (TAV) openings into the lower stack in a stair-step region;
• forming first sacrificial material in that which was formed by the (a), the (b), and the (c);
• forming an upper stack directly above the lower stack and the first sacrificial material, the upper stack comprising vertically-alternating upper first tiers and upper second tiers, the upper stack comprising the laterally-spaced memory-block regions;
• forming (d), (e), and (f), where,
• (d):
• horizontally-elongated upper trenches into the upper stack laterally-between immediately-laterally-adjacent of the memory-block regions, individual of the horizontally-elongated upper trenches extending to the first sacrificial material in individual of the horizontally-elongated lower trenches;
• (e):
• upper channel openings into the upper stack laterally-between the horizontally-elongated upper trenches, individual of the upper channel openings extending to the first sacrificial material in individual of the lower channel openings;
• and
• (f):
• upper TAV openings into the upper stack in the stair-step region, individual of the upper TAV openings extending to the first sacrificial material in individual of the lower TAV openings;
• forming second sacrificial material in that which was formed by the (d), the (e), and the (f);
• removing the first and second sacrificial materials to form upwardly-open vertically-extended trenches, upwardly-open vertically-extended channel openings, and upwardly-open vertically-extended TAV openings;
• and
• forming intervening material in the upwardly-open vertically-extended trenches, a channel-material string in individual of the upwardly-open vertically-extended channel openings, and conductive material in the upwardly-open vertically-extended TAV openings.

A memory array comprising strings of memory cells, comprising:

• laterally-spaced memory blocks individually comprising a vertical stack comprising alternating insulative tiers and conductive tiers, channel-material-string structures of memory cells extending through the insulative tiers and the conductive tiers;
• through-array-via (TAV) structures extending through the insulative tiers and the conductive tiers, individual of the TAV structures comprising an upper portion above and joined with a lower portion, the individual TAV structures comprising at least one external jog surface in a vertical cross-section where the upper and lower portions of the individual TAV structures join;
• individual of the channel-material-string structures comprising an upper portion above and joined with a lower portion, the individual channel-material-string structures comprising at least one external jog surface in the vertical cross-section where the upper and lower portions of the individual channel-material-string structures join;
• and
• horizontally-elongated walls laterally-between immediately-laterally-adjacent of the memory blocks, individual of the horizontally-elongated walls comprising an upper portion above and joined with a lower portion, the individual horizontally-elongated walls comprising at least one external jog surface in the vertical cross-section where the upper and lower portions of the horizontally-elongated walls join.