Memory Arrays Comprising Strings Of Memory Cells And Methods 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 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, a lowest of the first tiers comprising first sacrificial material;
• forming the vertically-alternating first tiers and second tiers of an upper portion of the stack above the lower portion, and forming channel-material strings that extend through the upper portion to the lower portion, material of the first tiers in the upper portion comprising second sacrificial material that is of different composition from material of the first tiers;
• forming horizontally-elongated trenches into the stack that are individually laterally-between immediately-laterally-adjacent of the memory-block regions, the trenches extending through the upper portion to the lowest first tier and exposing the first sacrificial material therein;
• isotropically etching the exposed first sacrificial material from the lowest first tier through the trenches;
• after the isotropically etching, forming conducting material in the lowest first tier that directly electrically couples together the channel material of the channel-material strings and the conductor material of the conductor tier;
• after forming the trenches, doping lateral-sidewall regions of the conducting material that are aside the individual trenches in the lowest first tier with an impurity;
• and
• etching the second sacrificial material from the first tiers in the upper portion through the trenches selectively relative to the doped lateral-sidewall regions of the conducting material in the lower portion.

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 above a conductor tier, strings of memory cells comprising channel-material strings that extend through the insulative tiers and the conductive tiers, conducting material in a lowest of the conductive tiers that directly electrically couples together the channel-material strings to conductor material of the conductor tier;
• intervening material laterally-between, vertically-along, and longitudinally-along immediately-laterally-adjacent of the memory blocks;
• and
• intermediate regions in the lowest first tier that are individually laterally between the intervening material and the conducting material, the intermediate regions comprising the conducting material having an impurity therein.