Methods of forming staircase-shaped connection structures of three-dimensional semiconductor devices
Provided is a staircase-shaped connection structure of a three-dimensional semiconductor device. The device includes an electrode structure on a substrate, the electrode structure including an upper staircase region, a lower staircase region, and a buffer region therebetween. The electrode structure includes horizontal electrodes sequentially stacked on the substrate, the horizontal electrodes include a plurality of pad regions constituting a staircase structure of each of the upper and lower staircase regions, and the buffer region has a width that is larger than that of each of the pad regions.
1. A method of fabricating a three-dimensional semiconductor device, comprising:
sequentially stacking a plurality of horizontal layers on a substrate to form a stack;
patterning some of the plurality of horizontal layers to form a first staircase region with at least one first multi-level stair;
patterning others of the plurality of horizontal layers to form a second staircase region with at least one second multi-level stair; and
patterning both of the first and second staircase regions at once to form single-level stairs in each of the first and second multi-level stairs,
wherein the first and second staircase regions are formed in such a way that a distance therebetween is larger than a width of each of the single-level stairs therein.
2. The method of claim 1 , wherein the first and second multi-level stairs are formed by at least one trimming process, and
the at least one trimming process comprises:
forming a mask pattern on the plurality of horizontal layers;
etching the plurality of horizontal layers to a first multi-layer depth using the mask pattern as an etch mask;
etching the mask pattern to reduce an occupying area of the mask pattern; and
etching the plurality of horizontal layers to a second multi-layer depth using the etched mask pattern as an etch mask.
3. The method of claim 1 , wherein the forming of the single-level stairs comprises:
forming a photoresist layer on the first and second staircase regions;
performing a photolithography process to form a photoresist pattern, in which at least one opening is formed across the first and second multi-level stairs;
etching the stack to a single-layer depth using the photoresist pattern as an etch mask; and
removing the photoresist pattern.
4. The method of claim 3 , wherein the photolithography process comprises exposing the first and second staircase regions at once, and the at least one opening is formed to continuously cross both of the first and second staircase regions.
5. The method of claim 3 , wherein the photolithography process comprises first and second exposure steps, which are performed to expose the first and second staircase regions, respectively.
6. The method of claim 5 , wherein the first and second exposure steps are performed using different process conditions of focal length.
7. The method of claim 5 , wherein the at least one opening comprises:
a first opening crossing the first staircase region; and
a second opening crossing the second staircase region,
wherein the first and second openings are formed spaced apart from each other between the first and second staircase regions.
8. The method of claim 1 , wherein the stack further comprises a cell array region,
the first staircase region is formed between the cell array region and the second staircase region, and
each of the first and second staircase regions has a stepwise-decreasing thickness in a direction away from the cell array region.
9. The method of claim 1 , further comprising:
forming vertical patterns penetrating the stack; and
forming a memory layer between the vertical patterns and the plurality of horizontal layers,
wherein the memory layer comprises a layer capable of realizing a charge-storing-type and/or variable-resistance-type memory element.
10. The method of claim 1 , wherein the patterning others of the plurality of horizontal layers to form the second staircase region is performed after the patterning some of the plurality of horizontal layers to form the first staircase region.
11. The method of claim 10 ,
wherein the distance between the first and second staircase regions is provided by a buffer region of the stack, and
wherein the patterning others of the plurality of horizontal layers to form the second staircase region comprises:
forming the at least one second multi-level stair to step down from the buffer region.
12. The method of claim 11 , further comprising forming an insulating layer on the first and second staircase regions, wherein the insulating layer comprises a monotonically increasing thickness in a direction from the first staircase region toward the second staircase region.
13. The method of claim 12 , further comprising:
forming a mask on the buffer region and the first and second staircase regions, wherein the patterning both of the first and second staircase regions at once is performed using the mask as an etch mask; and
removing the mask before the forming the insulating layer on the first and second staircase regions.
14. The method of claim 1 , wherein the patterning both of the first and second staircase regions at once comprises forming the single-level stairs by etching to a depth equal to or smaller than a vertical pitch of the plurality of horizontal layers.