Memory circuitry and method used in forming memory circuitry
Memory circuitry comprising strings of memory cells comprises a stack comprising vertically-alternating insulative tiers and conductive tiers. Channel-material strings of memory cells extend through the insulative tiers and the conductive tiers in a memory-array region. The insulative tiers and the conductive tiers extend from the memory-array region into a stair-step region. The stair-step region comprises a cavity comprising a flight of stairs extending along a first direction. Multiple different-depth and height-sequential treads in individual of the stairs extend along a second direction that is orthogonal to the first direction. Individual of the multiple different-depth treads comprise conducting material of one of the conductive tiers. The cavity comprises a pair of laterally-opposing outermost sidewalls relative to the second direction and that individually extend along the first direction. The multiple different-depth and height-sequential treads in the individual stairs comprise a single flight of said treads that extends along the second direction from one of the laterally-opposing outermost sidewalls to the other of the laterally-opposing outermost sidewalls. Methods are disclosed.
1 . A method used in forming memory circuitry, comprising:
forming a stack comprising vertically-alternating first tiers and second tiers, the stack extending from a memory-array region into a stair-step region, the stair-step region comprising a cavity comprising a flight of stairs extending along a first direction, the first tiers being conductive and the second tiers being insulative at least in a finished-circuitry construction, the cavity comprising a pair of laterally-opposing outermost sidewalls relative to a second direction that is orthogonal to the first direction and that individually extend along the first direction;
forming a series of first and second spacers in the cavity, the first and second spacers extending along the first direction directly above the flight of stairs, the first spacers having a different composition than the second spacers, the series of spacers having first spacers alternating with second spacers along the second direction;
forming masking material directly above the series of first and second spacers, the masking material comprising an opening there-through that exposes a single spacer of the first and second spacers, the single spacer being laterally-closest to one of the laterally-opposing outermost sidewalls, the masking material covering all remaining of the first and second spacers; and
using the masking material in a plurality of alternating etching and lateral-trimming steps that progressively widen the opening and form multiple different-depth treads in individual of the stairs along the second direction, each of the lateral-trimming steps individually exposing a single next-in-series spacer comprised by the series of first and second spacers through the masking material and covering all then-remaining, if any, of the first and second spacers with the masking material, the etching steps individually removing only one of the alternating first and second spacers as a result of the respective lateral-trimming step followed by etching through one of the first tiers and one of the second tiers that was there-below, individual of the treads comprising conducting material of individual of the first tiers in the finished-circuitry construction.
2 . The method of claim 1 wherein forming at least some of the series of first and second spacers comprises:
forming a spacer-forming layer above and within the cavity; and
anisotropically etching the spacer-forming layer above and within the cavity.
3 . The method of claim 2 wherein less-than-all of the spacers are formed by anisotropically etching the respective spacer-forming layer within the cavity.
4 . The method of claim 3 wherein a majority of the collective first and second spacers is formed by the anisotropically etching of the respective spacer-forming layer within the cavity.
5 . The method of claim 1 wherein the masking material comprises photoresist.
6 . The method of claim 1 wherein each of the different compositions is different from those of the first and second tiers.
7 . The method of claim 1 wherein one of the different compositions is carbon.
8 . The method of claim 1 wherein one of the different compositions is polysilicon.
9 . The method of claim 1 wherein one of the different compositions is carbon and the other of the different compositions is polysilicon.
10 . The method of claim 1 wherein total number of the alternating first and second spacers in the cavity is five.
11 . The method of claim 1 wherein the individual stairs have total number of the multiple different-depth treads in the finished-circuitry construction that is five.
12 . The method of claim 1 wherein,
total number of the alternating first and second spacers in the series is five; and
the individual stairs have total number of the multiple different-depth treads in the finished-circuitry construction that is five.
13 . The method of claim 1 wherein the multiple different-depth treads in the finished-circuitry construction are height-sequential along the second direction in the individual stairs.
14 . The method of claim 13 wherein the multiple different-depth and height-sequential treads in the individual stairs comprise a single flight of said treads that extends along the second direction from one of the laterally-opposing outermost sidewalls to the other of the laterally-opposing outermost sidewalls.
15 . The method of claim 14 wherein the individual stairs have total number of the multiple different-depth treads in the finished-circuitry construction that is five.
16 . The method of claim 1 wherein the first and second spacers are of the same lateral-width in the second direction.
17 . A method used in forming memory circuitry, comprising:
forming a stack comprising vertically-alternating first tiers and second tiers, the stack extending from a memory-array region into a stair-step region, the stair-step region comprising a cavity comprising a flight of stairs extending along a first direction, the first tiers being conductive and the second tiers being insulative at least in a finished-circuitry construction, the cavity comprising a pair of laterally-opposing outermost sidewalls relative to a second direction that is orthogonal to the first direction and that individually extend along the first direction;
forming fill material in the cavity directly above the flight of stairs;
forming masking material directly above the fill material, the masking material comprising an opening there-through that exposes a portion of the fill material that is laterally-closest to one of the laterally-opposing outermost sidewalls and extends there-along in the first direction, the masking material covering all remaining of the fill material but for the portion; and
using the masking material in a plurality of alternating etching and lateral-trimming steps that progressively widen the opening from the laterally-closest sidewall along the first direction and form multiple different-depth treads in individual of the stairs along the second direction, the lateral-trimming steps individually exposing a next-in-succession portion of the fill material that extends along the first direction and covering all then-remaining, if any, of the fill material, the etching steps individually removing the respective next-in-succession portion as a result of the respective lateral-trimming step followed by etching through one of the first tiers and one of the second tiers that was there-below, individual of the treads comprising conducting material of individual of the first tiers in the finished-circuitry construction.
18 . The method of claim 17 wherein the masking material comprises photoresist.
19 . The method of claim 17 wherein the individual stairs have total number of the multiple different-depth treads that is five.
20 . The method of claim 17 wherein the multiple different-depth treads in in the finished-circuitry construction are height-sequential along the second direction in the individual stairs.
21 . The method of claim 20 wherein the multiple different-depth and height-sequential treads in the individual stairs comprise a single flight of said treads that extends along the second direction from one of the laterally-opposing outermost sidewalls to the other of the laterally-opposing outermost sidewalls.
22 . The method of claim 21 wherein the individual stairs have total number of the multiple different-depth treads in the finished-circuitry construction that is five.