Multi-Layer Mask Patterning for High-Aspect-Ratio NAND Memory Trenches
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Solution Overview
Problem
As the number of stacks in NAND semiconductor memory devices increases to enhance memory capacity, fine patterning of the stacked body becomes increasingly difficult due to the challenges in maintaining precise etching configurations and preventing deformation of mask layers, leading to issues in achieving the desired etched structure.
Innovation Solution
The method involves forming a first mask layer with a shielding portion and opening, followed by a second mask layer with intersecting openings, allowing for selective removal of layers at the crossing points to maintain etching resistance and prevent deformation, thereby enabling precise formation of memory trenches and word lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of stacks is increased to enhance memory capacity, then memory capacity is improved, but fine patterning becomes difficult due to mask layer deformation
Solution Approach 1:
The patent divides the single mask layer into multiple mask layers (first mask layer and second mask layer) with different functions. The first mask layer forms initial patterns, while the second mask layer forms intersecting patterns, allowing complex three-dimensional structures to be created through sequential patterning steps without requiring excessively fine single-step patterning
Solution Approach 2:
The patent transitions from two-dimensional planar patterning to three-dimensional stacked patterning by forming mask layers at different heights and orientations. The intersecting mask layers create vertical and horizontal patterns that define the three-dimensional memory cell structure, enabling increased storage density through vertical stacking
2Quantity of substance
If the number of stacks is increased to enhance memory capacity, then memory capacity is improved, but etching configuration control becomes difficult
Solution Approach 1:
The etching process is segmented into multiple sequential steps, each controlled by a specific mask layer. The first etching step creates initial trenches guided by the first mask layer, followed by a second etching step that creates intersecting structures guided by the second mask layer, allowing precise control of complex three-dimensional etching configurations
Solution Approach 2:
The first mask layer and first etching step are performed as preliminary actions to create the basic structural framework before the second mask layer is formed. This preliminary structuring simplifies subsequent patterning steps and ensures that the final three-dimensional configuration is achieved with high precision
3Strength
If mask layer thickness is increased to maintain etching resistance, then etching resistance is improved, but mask layer deformation increases
Solution Approach 1:
The mask layer system is segmented into multiple thinner layers rather than using a single thick mask layer. Each mask layer has optimized thickness sufficient for its specific etching step, maintaining adequate etching resistance while avoiding the deformation issues associated with excessively thick single mask layers
Solution Approach 2:
The first mask layer acts as an intermediary structure that is partially removed during the etching process to form the final pattern. This intermediary approach allows the mask to provide necessary structural support and etching resistance during processing while being designed to be selectively removed to achieve the desired final configuration
Data Source
AI summary
A method for manufacturing a semiconductor device includes forming a first mask layer having a first opening on an underlying layer; forming a first layer in a space where the underlying layer is selectively removed via the first opening; forming a second mask layer on the first mask layer and the first layer, the second mask layer having a second opening crossing the first opening; and selectively removing the first layer at a portion where the first opening and the second opening cross. At least one of the first and second mask layers having openings including the first or second opening, the openings being arranged in the first mask layer along a first direction, and/or being arranged in the second mask layer along a second direction, the first opening crossing the second opening in the first direction, and the second opening crossing the first opening in the second direction.