Elevationally-extending strings of memory cells individually comprising a programmable charge storage transistor and methods of processing silicon nitride-comprising materials
A method comprises forming material to be etched over a substrate. An etch mask comprising a silicon nitride-comprising region is formed elevationally over the material. The etch mask comprises an elevationally-extending mask opening in the silicon nitride-comprising region that has a minimum horizontal open dimension that is greater in an elevationally-innermost portion of the region than in an elevationally-outermost portion of the region. The elevationally-outermost portion has a greater etch rate in at least one of HF and H 3 PO 4 than does the elevationally-innermost portion. The etch mask is used as a mask while etching an elevationally-extending mask opening into the material. The silicon nitride-comprising region is exposed to at least one of HF and H 3 PO 4 to increase the minimum horizontal open dimension in the elevationally-outermost portion to a greater degree than increase, if any, in the minimum horizontal open dimension in the elevationally-innermost portion. Other aspects and embodiments, including structure independent of method of manufacture, are disclosed.
1. 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 comprising boron, the encircling silicon nitride-comprising material comprising an elevationally-innermost portion having less boron content, if any, than the elevationally-outermost portion.
2. The string of memory cells of claim 1 wherein said boron content is constant elevationally through each of the elevationally-outermost portion and the elevationally-innermost portion.
3. The string of memory cells of claim 1 wherein boron is in the elevationally-innermost portion, said boron content being variable elevationally through each of the elevationally-outermost portion and the elevationally-innermost portion.
4. The string of memory cells of claim 1 wherein the elevationally-outermost portion has 1 to 20 atomic percent boron.
5. The string of memory cells of claim 1 wherein the elevationally-innermost portion has zero to 0.001 atomic percent boron.
6. The string of memory cells of claim 1 wherein difference in said boron content is along a stepped gradient.
7. The string of memory cells of claim 6 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.
8. The string of memory cells of claim 1 wherein difference in said boron content is along a linear gradient.
9. The string of memory cells of claim 8 wherein the linear gradient is straight.
10. The string of memory cells of claim 9 wherein the linear gradient is from an elevationally-outermost surface of the elevationally-outermost portion to an elevationally-innermost surface of the elevationally-innermost portion.
11. The string of memory cells of claim 8 wherein the linear gradient is curved.
12. The string of memory cells of claim 11 wherein the linear gradient is from an elevationally-outermost surface of the elevationally-outermost portion to an elevationally-innermost surface of the elevationally-innermost portion.