3D Memory Staircase Structure Segmentation
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Solution Overview
Problem
The challenge in 3D memory technology is to increase storage density while reducing the lateral dimensions of staircase structures, as scaling down the staircase region leads to manufacturing difficulties due to increased aspect ratios and reduced effective storage capacity per unit area.
Innovation Solution
The method involves forming an alternating dielectric stack with offset steps and staircase structures in both x- and y-directions, using a repetitive etch-trim process to create multiple dielectric layer pairs, allowing for the formation of staircase steps with accessible dielectric layers, thereby enhancing storage density without increasing the staircase step height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of vertically stacked memory cells is increased to increase storage capacity, then storage density is improved, but the lateral dimensions of the staircase structure increase, reducing effective storage capacity per area
Solution Approach 1:
The staircase structure is divided into multiple segments along both x and y directions, creating a grid-like pattern of staircase steps. This segmentation allows the structure to accommodate more vertically stacked memory cells while maintaining compact lateral dimensions, as each segment can independently access its portion of the stacked cells without requiring excessive lateral space.
Solution Approach 2:
The invention transitions from a traditional single-direction staircase structure to a two-directional staircase structure with steps in both x and y directions. This dimensional expansion allows the staircase to efficiently access vertically stacked memory cells in a three-dimensional space, increasing storage capacity per unit area by utilizing both lateral dimensions rather than just one.
2Quantity of substance
If the lateral dimensions of the staircase structure are reduced to increase storage density, then storage density is improved, but manufacturing becomes more difficult due to increased aspect ratios
Solution Approach 1:
By segmenting the staircase structure into multiple smaller steps in both x and y directions, the invention reduces the aspect ratio of individual staircase steps while maintaining overall compact lateral dimensions. This segmentation makes the structure more manufacturable, as each individual step has more manageable dimensions and aspect ratios compared to a single large staircase structure.
Solution Approach 2:
The invention changes the geometric parameters of the staircase structure by introducing steps in both x and y directions, transforming the aspect ratio characteristics. This parameter change allows the structure to achieve compact lateral dimensions without excessively high aspect ratios, thereby improving ease of manufacture while maintaining high storage density.
3Ease of manufacture
If traditional staircase structures are used, then manufacturing is simpler, but storage density is lower due to larger lateral dimensions
Solution Approach 1:
The invention extends the traditional one-directional staircase structure into two dimensions by adding steps in both x and y directions. This dimensional enhancement increases storage density by allowing more vertically stacked memory cells to be accessed within the same lateral footprint, while the manufacturing process remains relatively straightforward by extending existing staircase fabrication techniques to two directions.
Data Source
AI summary
Staircase structures for a three-dimensional (3D) memory device are disclosed. In some embodiments, the method includes disposing an alternating dielectric stack on a substrate with first and second dielectric layers alternatingly stacked on top of each other. Next, multiple division blocks can be formed in a staircase region. Each division block includes a first plurality of staircase steps in the first direction. Each staircase step in the first direction has two or more dielectric layer pairs. Then, a second plurality of staircase steps along a second direction, perpendicular to the first direction, can be formed. Each staircase step in the second direction includes the first plurality of staircase steps along the first direction. The method further includes forming an offset number of dielectric layer pairs between the multiple division blocks such that each dielectric layer pair is accessible from a top surface of a staircase step.