Elevationally-extending strings of memory cells individually comprising a programmable charge storage transistor and methods of processing silicon nitride-comprising materials

An elevationally-extending string of memory cells individually comprising a programmable charge storage transistor, comprising:

• vertically-alternating tiers of insulative material and control gate material;
• a channel pillar extending elevationally through multiple of the vertically-alternating tiers and comprising a projecting portion extending elevationally outward of the elevationally-outermost tier of control gate material;
• tunnel insulator, programmable charge storage material, and control gate blocking insulator between the channel pillar and the control gate material of individual of the tiers of the control gate material;
• and
• silicon nitride-comprising material encircling at least some of the projecting portion of the channel pillar, the encircling silicon nitride-comprising material comprising an elevationally-outermost portion and an elevationally-innermost portion, the elevationally-outermost portion having greater intrinsic mechanical stress in the tensile direction than does the elevationally-innermost portion, difference in said intrinsic mechanical stress being along a stepped gradient, and comprising three steps in the stepped gradient between an elevationally-outermost surface of the elevationally-outermost portion to an elevationally-innermost surface of the elevationally-innermost portion.

An elevationally-extending string of memory cells individually comprising a programmable charge storage transistor, comprising:

• vertically-alternating tiers of insulative material and control gate material;
• a channel pillar extending elevationally through multiple of the vertically-alternating tiers and comprising a projecting portion extending elevationally outward of the elevationally-outermost tier of control gate material;
• tunnel insulator, programmable charge storage material, and control gate blocking insulator between the channel pillar and the control gate material of individual of the tiers of the control gate material;
• and
• silicon nitride-comprising material encircling at least some of the projecting portion of the channel pillar, the encircling silicon nitride-comprising material comprising an elevationally-outermost portion and an elevationally-innermost portion, the elevationally-outermost portion having greater intrinsic mechanical stress in the tensile direction than does the elevationally-innermost portion, difference in said intrinsic mechanical stress being along a linear gradient.

An elevationally-extending string of memory cells individually comprising a programmable charge storage transistor, comprising:

• vertically-alternating tiers of insulative material and control gate material;
• a channel pillar extending elevationally through multiple of the vertically-alternating tiers and comprising a projecting portion extending elevationally outward of the elevationally-outermost tier of control gate material;
• tunnel insulator, programmable charge storage material, and control gate blocking insulator between the channel pillar and the control gate material of individual of the tiers of the control gate material;
• and
• silicon nitride-comprising material encircling at least some of the projecting portion of the channel pillar, the encircling silicon nitride-comprising material comprising an elevationally-innermost portion comprising carbon, the encircling silicon nitride-comprising material comprising an elevationally-outermost portion having less carbon content, if any, than the elevationally-innermost portion, carbon being in the elevationally-outermost portion, said carbon content being variable elevationally through each of the elevationally-outermost portion and the elevationally-innermost portion.

An elevationally-extending string of memory cells individually comprising a programmable charge storage transistor, comprising:

• vertically-alternating tiers of insulative material and control gate material;
• a channel pillar extending elevationally through multiple of the vertically-alternating tiers and comprising a projecting portion extending elevationally outward of the elevationally-outermost tier of control gate material;
• tunnel insulator, programmable charge storage material, and control gate blocking insulator between the channel pillar and the control gate material of individual of the tiers of the control gate material;
• and
• silicon nitride-comprising material encircling at least some of the projecting portion of the channel pillar, the encircling silicon nitride-comprising material comprising an elevationally-innermost portion comprising carbon, the encircling silicon nitride-comprising material comprising an elevationally-outermost portion having less carbon content, if any, than the elevationally-innermost portion, difference in said carbon content being along a stepped gradient, and comprising three steps in the stepped gradient between an elevationally-outermost surface of the elevationally-outermost portion to an elevationally-innermost surface of the elevationally-innermost portion.

An elevationally-extending string of memory cells individually comprising a programmable charge storage transistor, comprising:

• vertically-alternating tiers of insulative material and control gate material;
• a channel pillar extending elevationally through multiple of the vertically-alternating tiers and comprising a projecting portion extending elevationally outward of the elevationally-outermost tier of control gate material;
• tunnel insulator, programmable charge storage material, and control gate blocking insulator between the channel pillar and the control gate material of individual of the tiers of the control gate material;
• and
• silicon nitride-comprising material encircling at least some of the projecting portion of the channel pillar, the encircling silicon nitride-comprising material comprising an elevationally-innermost portion comprising carbon, the encircling silicon nitride-comprising material comprising an elevationally-outermost portion having less carbon content, if any, than the elevationally-innermost portion, difference in said carbon content being along a linear gradient.