Substrate processing method and device manufactured by the same
Provided is a substrate processing method that may prevent the non-uniformity of the thickness of landing pads deposited on each step in a vertical NAND device having a stepped structure. The substrate processing method includes stacking, a plurality of times, a stack structure including an insulating layer and a sacrificial layer and etching the stack structure to form a stepped structure having an upper surface, a lower surface, and a side surface connecting the upper surface and the lower surface. The method also includes forming a barrier layer on the stepped structure, forming a mask layer on the barrier layer and exposing at least a portion of the barrier layer by etching at least a portion of the mask layer with a first etching solution The method further includes etching the exposed barrier layer with a second etching solution and etching the mask layer with a third etching solution.
1. A substrate processing method comprising:
alternately stacking n first silicon oxide layers and n first silicon nitride layers in a first direction, where n is a natural number greater than or equal to 2;
etching the stacked first silicon oxide layers and first silicon nitride layers to form an n-story stepped structure having an upper surface, a lower surface, and a side surface connecting the upper surface and the lower surface;
forming a second silicon nitride layer on the upper surface, the lower surface, and the side surface of the n-story stepped structure;
selectively densifying the second silicon nitride layer on the upper surface and the lower surface;
forming a second silicon oxide layer on the second silicon nitride layer;
selectively densifying the second silicon oxide layer on the upper surface and the lower surface;
removing a non-densified portion of the second silicon oxide layer;
removing a non-densified portion of the second silicon nitride layer; and
removing a densified portion of the second silicon oxide layer.
2. The substrate processing method of claim 1 , wherein a thickness of a second silicon nitride layer densified during the selective densifying of the second silicon nitride layer does not change during the removing of the non-densified portions of the second silicon oxide layer and the second silicon nitride layer, and the removing of the densified portion of the second silicon oxide layer.
3. The substrate processing method of claim 1 , wherein:
the removing of the non-densified portion of the second silicon oxide layer comprises using a first etching solution, and
the removing of the densified portion of the second silicon oxide layer comprises using a second etching solution.
4. The substrate processing method of claim 3 , wherein:
the first etching solution and the second etching solution are the same solution, and
an etching time of the removing of the densified portion of the second silicon oxide layer is longer than an etching time of the removing of the non-densified portion of the second silicon oxide layer.
5. The substrate processing method of claim 1 , wherein:
each step of the n-story stepped structure comprises:
the first silicon oxide layer formed at a lower portion thereof; and
the first silicon nitride layer formed on the first silicon oxide layer,
a second silicon nitride layer formed on a first silicon nitride layer forming a kth step (k: a natural number greater than or equal to 2 and smaller than or equal to n) of the n-story stepped structure, wherein the second silicon nitride layer comprises, after the removing of the non-densified portion of the second silicon nitride layer:
a first sidewall facing one side of a first silicon oxide layer forming a (k+1)th step of the n-story stepped structure; and
a second sidewall facing the first sidewall,
each of a first sidewall and a second sidewall of a second silicon nitride layer formed on each step of the n-story stepped structure has a portion recessed in a side direction thereof, after the removing of the non-densified portion of the second silicon nitride layer,
the recessed portion extends in a second direction, and
the second direction is perpendicular to the first direction.
6. The substrate processing method of claim 5 , wherein:
second silicon nitride layers formed on each step of the n-story stepped structure are formed to be spaced apart from each other in a third direction, after the removing of the non-densified portion of the second silicon nitride layer, and
the third direction is perpendicular to the first direction and the second direction.
7. The substrate processing method of claim 1 , wherein second silicon nitride layers formed on each step of the n-story stepped structure have different densities, after the selective densifying of the second silicon nitride layer.
8. The substrate processing method of claim 1 , wherein second silicon nitride layers formed on each step of the n-story stepped structure have the same thickness in the first direction, after the removing of the non-densified portion of the second silicon nitride layer.