3D Memory Stepped Trench Etching for Stable Layer Integration
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Solution Overview
Problem
Three-dimensional semiconductor memory devices face challenges in structural stability and manufacturing process stability as the number of cell layers increases, leading to defects and reduced integration density.
Innovation Solution
A method for forming a semiconductor device involving the creation of a stacked structure with stepped trenches and grooves of varying depths, using a combination of hard mask materials and photoresist patterns to etch and extend trench depths, allowing for increased layer integration while maintaining structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of cell layers is increased to improve integration density, then the degree of integration improves, but structural stability deteriorates
Solution Approach 1:
The patent divides the continuous etching process into multiple discrete steps with different photoresist patterns (first photoresist pattern, second photoresist pattern, third photoresist pattern) that sequentially expose different portions of the stacked structure. This segmentation allows precise control over etching depth at each stage, enabling the formation of stepped trenches with controlled depths while maintaining structural integrity throughout the process.
Solution Approach 2:
The patent applies preliminary protective actions by forming an etch stop pattern with hard mask material before the etching process begins. This etch stop pattern serves as a protective layer that prevents over-etching and structural damage. Additionally, the first photoresist pattern is applied to fill and protect portions of openings before subsequent etching steps, ensuring that only intended regions are etched to the required depths.
2Quantity of substance
If the number of cell layers is increased to improve integration density, then the degree of integration improves, but manufacturing process stability deteriorates
Solution Approach 1:
The manufacturing process is segmented into multiple discrete etching steps, each with its own photoresist pattern and etching parameters. This segmentation transforms a single complex high-risk etching operation into multiple manageable steps, where each step etches a controlled portion of the stacked structure. This reduces process variability and defect formation compared to attempting to etch all layers in a single step.
Solution Approach 2:
The patent introduces intermediary elements including the etch stop pattern with hard mask material that acts as a mediator between the etching process and the stacked structure. This intermediary layer provides a controlled stop point for etching, preventing runaway etching that could compromise manufacturing stability. The photoresist patterns also serve as intermediaries that selectively protect or expose regions during each etching step.
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 patent segments the etching process into multiple steps, each handling a specific depth range or region of the stacked structure. The first etching step etches to a first depth, the second etching step extends to a second depth greater than the first, and subsequent steps continue this pattern. This segmentation maintains manufacturing precision by ensuring that each etching step operates within optimal parameter ranges, unlike a single deep etch that would be difficult to control.
Solution Approach 2:
Each photoresist pattern selectively exposes only the necessary portions of the stacked structure for the current etching step, rather than exposing the entire structure. The first photoresist pattern fills a first portion of openings and exposes a second portion, the second photoresist pattern covers certain regions while exposing others, and so on. This partial action approach prevents unnecessary etching that could lead to defects while maintaining the required etching precision.
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
The method enhances the stability and integration density of three-dimensional semiconductor memory devices, reducing defects and costs by using a combination of hard mask materials and photoresist patterns to create precise trench structures.
Implementation Method 1
forming an etch stop pattern having a hard mask material over a top surface of the stacked structure... etching the second portion of the openings using the etch stop pattern as an etch mask
Implementation Method 2
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
Implementation Method 3
etching the second portion of the openings using the etch stop pattern as an etch mask to extend a bottom of the stepped trenches exposed by the second portion of the openings to a second depth lower than the first depth
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.