3D Memory Stepped Trench Etching for High-Layer Stability
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Solution Overview
Problem
The challenge in three-dimensional semiconductor memory devices is the reduction in structural stability and manufacturing process stability as the number of cell layers increases, leading to defects and reduced integration.
Innovation Solution
A method is employed to form a stacked structure with stepped trenches and etch stop patterns, using photoresist patterns to etch grooves of varying depths, and filling these grooves with insulating material, thereby enhancing structural stability and integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of cell layers is increased to improve integration, then the degree of integration is improved, but structural stability and manufacturing process stability are reduced
Solution Approach 1:
The patent divides the etching process into multiple stages with different photoresist patterns applied sequentially. First photoresist patterns are used to etch initial trenches, then removed and replaced with second photoresist patterns to etch additional trenches at different depths. This segmentation allows precise control over trench formation in high-layer-count devices without compromising structural stability.
Solution Approach 2:
The patent applies preliminary actions by forming support structures and etch stop patterns before performing deep etching operations. Etch stop patterns are deposited at specific depths to prevent over-etching, and support structures are formed to maintain structural integrity during subsequent processing steps. This preliminary preparation enables safe increase in layer count while maintaining reliability.
2Productivity
If the number of cell layers is increased to improve integration, then the degree of integration is improved, but manufacturing process stability is reduced leading to defects
Solution Approach 1:
The manufacturing process is segmented into multiple etching stages, each with its own photoresist pattern and etch parameters. This allows optimization of each etching step independently, maintaining high precision even as total layer count increases. Each stage targets specific depth ranges, preventing cumulative errors that would occur in single-step etching of deep trenches.
Solution Approach 2:
Etch stop patterns serve as intermediary layers that mediate between the etching process and the underlying structure. These patterns are deposited at predetermined depths and provide controlled termination points for etching, ensuring consistent trench depths across multiple layers. This intermediary mechanism compensates for variations in etch rate and maintains manufacturing precision.
3Ease of manufacture
If conventional etching processes are used for single layer devices, then the process is simple, but defects occur when more layers are present
Solution Approach 1:
The etching process is segmented into multiple sequential steps, each handling a portion of the total trench depth. First etching steps create initial trenches using first photoresist patterns, then second etching steps extend trenches or create additional trenches using second photoresist patterns. This segmentation maintains process simplicity by using repeated, standardized steps rather than requiring entirely new complex processes.
Solution Approach 2:
The manufacturing process employs periodic action by repeating cycles of photoresist application, etching, and photoresist removal. Each cycle targets specific depth ranges or regions, and the repetition of this standardized cycle maintains process simplicity while achieving the complex result of forming trenches through multiple layers without defects.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in a stable three-dimensional semiconductor memory device with reduced defects and improved integration, achieved through the formation of grooves with different depths and asymmetric sidewalls, allowing for a higher number of layers without compromising stability.
Implementation Method 1
forming a first photoresist pattern over the etch stop pattern, the photoresist pattern filling a first portion of the openings and exposing a second portion of the openings, and etching the second portion of the openings using the etch stop pattern as an etch mask
Data Source
AI summary
A process of forming a 3D memory device includes forming a stacked structure with a plurality of stacked layers, etching the stacked structure to form stepped trenches each comprising a plurality of steps, forming a hard mask layer with a plurality of openings over the stepped trenches, forming a photoresist layer over the hard mask layer, and etching through the plurality of openings using the hard mask layer and the photoresist layers as an etch mask to extend a bottom of the stepped trenches to a lower depth.