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

Abstract

A memory array comprising strings of memory cells comprises 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 extend through the insulative tiers and the conductive tiers. The conductor tier comprises upper conductor material directly above and directly against lower conductor material of different composition from that of the upper conductor material. A through-array-via (TAV) region is included and comprises TAVs individually comprising the upper conductor material, the lower conductor material, and a conducting material that is directly below the conductor tier. The lower conductor material is directly against the conducting material and comprises at least one of (a) and (b), where, (a): a metal-rich refractory metal nitride; and (b): a stoichiometric or non-stoichiometric refractory metal nitride directly above and directly against one of (1), (2), or (3), where: (1): an elemental metal; (2): an alloy of at least two elemental metals; and (3): a metal-rich refractory metal nitride of different composition from that of the stoichiometric or non-stoichiometric refractory metal nitride. Methods are also disclosed.