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 lower portion of a stack that will comprise vertically-alternating first tiers and second tiers, the stack comprising laterally-spaced memory-block regions, material of the first tiers being of different composition from material of the second tiers, the lower portion comprising lower first insulating material;
• forming sacrificial rails in the lower portion that are individually between immediately-laterally-adjacent of the memory-block regions and that extend through the lower first insulating material;
• forming upper second insulating material directly above the lower first insulating material and directly above the sacrificial rails, the upper second insulating material comprising a same composition as that of the lower first insulating material, the same composition being other than undoped stoichiometric silicon dioxide and other than stoichiometric silicon nitride;
• forming the vertically-alternating first tiers and second tiers of an upper portion of the stack above the upper second insulating material and above the sacrificial rails, and forming channel-material strings that extend through the upper portion to the lower portion;
• forming horizontally-elongated trenches into the stack that are individually between the immediately-laterally-adjacent memory-block regions and extend through the upper portion and through the upper second insulating material to the sacrificial rail immediately-therebelow;
• and
• removing the sacrificial rails through the trenches.

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

• forming a lower portion of a stack that will comprise vertically-alternating first tiers and second tiers, the stack comprising laterally-spaced memory-block regions, material of the first tiers being of different composition from material of the second tiers, the lower portion comprising sacrificial rails that are individually between immediately-laterally-adjacent of the memory-block regions;
• forming insulating material aside and directly above the sacrificial rails, the insulating material comprising material other than undoped stoichiometric silicon dioxide and other than stoichiometric silicon nitride;
• forming the vertically-alternating first tiers and second tiers of an upper portion of the stack above the insulating material and above the sacrificial rails, and forming channel-material strings that extend through the upper portion to the lower portion;
• forming horizontally-elongated trenches into the stack that are individually between the immediately-laterally-adjacent memory-block regions and extend through the upper portion and through the insulating material to the sacrificial rail immediately-therebelow;
• and
• removing the sacrificial rails through the trenches.

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, the channel-material strings directly electrically coupling to conductor material of the conductor tier;
• the insulative tier immediately-above a lowest of the conductive tiers comprising a lower first insulating material and an upper second insulating material above the upper first insulating material, the upper second insulating material being of different composition from that of the lower first insulating material;
• and
• intervening material laterally-between and longitudinally-along immediately-laterally-adjacent of the memory blocks.

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, the channel-material strings directly electrically coupling to conductor material of the conductor tier;
• the insulative tier immediately-above a lowest of the conductive tiers comprising a lower first insulating material and an upper second insulating material above the upper first insulating material, the upper second insulating material comprising a same composition as that of the lower first insulating material, the same composition being other than undoped stoichiometric silicon dioxide and other than stoichiometric silicon nitride;
• and
• intervening material laterally-between and longitudinally-along immediately-laterally-adjacent of the memory blocks.

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, the channel-material strings directly electrically coupling to conductor material of the conductor tier;
• the insulative tier immediately-above a lowest of the conductive tiers comprising insulating material comprising material other than undoped stoichiometric silicon dioxide and other than stoichiometric silicon nitride;
• and
• intervening material laterally-between and longitudinally-along immediately-laterally-adjacent of the memory blocks.