3D Flash Memory Stepped Word Line Integration
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Solution Overview
Problem
Three-dimensional flash memory technologies face challenges in maximizing integration due to wasted area in stepped portions and the need for repetitive etching processes, which reduces the degree of integration and increases manufacturing complexity.
Innovation Solution
The proposed solution involves forming memory cell strings in both plane and stepped portions of word lines, with contacts minimized to specific partial areas, and dividing word lines into upper and lower groups for simultaneous etching, reducing the number of etching operations and optimizing the stair shape's dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If contacts are formed on all word lines including stepped portions, then electrical connection is ensured, but memory area is wasted and integration is reduced
Solution Approach 1:
The patent applies local quality by differentiating the treatment of word lines based on their position. Plane portion word lines receive contacts for electrical connection, while stepped portion word lines are left without contacts to preserve memory area. This selective approach ensures electrical connection where needed while maximizing memory capacity in the stepped portions.
2Ease of manufacture
If memory cell strings are formed only on plane portions, then manufacturing is simplified, but significant area is wasted in stepped portions
Solution Approach 1:
The patent segments the substrate into plane portions and stepped portions, allowing different structures to be formed in each region. Memory cell strings are formed in both plane and stepped portions independently, utilizing the stepped portions for additional storage while maintaining manufacturing feasibility through the modular nature of the process.
Solution Approach 2:
The patent transitions from two-dimensional planar memory to three-dimensional stacked memory by forming memory cell strings in the stepped portions at different height levels. This vertical stacking enables additional memory capacity without increasing the footprint area, effectively utilizing the third dimension.
3Shape
If repetitive trimming and etching operations are performed to form stair shape, then word line structure is achieved, but manufacturing complexity and process time increase
Solution Approach 1:
The patent performs preliminary actions by forming the mold structure with the stair shape configuration before depositing word lines. This approach allows the word lines to naturally conform to the pre-formed stair shape, eliminating the need for multiple subsequent trimming and etching operations to create the stepped structure.
Solution Approach 2:
The patent introduces a mold structure as an intermediary element that defines the stair shape. This mold serves as a template that guides the formation of word lines and memory cell strings, simplifying the overall manufacturing process by providing a pre-configured structure rather than requiring complex post-processing steps.
Data Source
AI summary
A three-dimensional flash memory and a method of manufacturing the three-dimensional flash memory are provided. The three-dimensional flash memory may have a structure for achieving integration, and may be manufactured using a manufacturing method for efficiently forming word lines.