3D Memory Etch Stop Structures for Precise Vertical NAND Fabrication
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Solution Overview
Problem
Existing methods for manufacturing three-dimensional memory devices face challenges in efficiently forming vertical NAND strings with precise etch stop structures, leading to inefficiencies in the manufacturing process.
Innovation Solution
A method involving the formation of alternating stacks of insulating and spacer material layers, followed by selective etching and replacement with conductive layers, to create etch stop semiconductor material layers, enabling the formation of vertical memory openings and channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used to form vertical NAND strings, then the manufacturing process becomes complex and inefficient, but achieving precise etch stop structures is necessary for device integrity
Solution Approach 1:
The patent applies preliminary action by forming sacrificial plugs and etch stop structures at defined intervals within the alternating stack before completing the full memory device fabrication. These pre-formed structures serve as guides and stopping points for subsequent etching operations, ensuring precise vertical NAND string formation without requiring complex post-processing steps.
Solution Approach 2:
The patent uses sacrificial plugs as intermediary structures that facilitate the formation of etch stop structures. These temporary plugs are formed, patterned, and etched to create the etch stop structures, which then serve as intermediaries to control the etching depth and position during vertical NAND string formation. The sacrificial plugs are later removed, having served their mediating function in the manufacturing process.
2Manufacturing precision
If multiple etching steps are performed to create vertical memory openings, then manufacturing time increases, but precise control over opening depth and position is achieved
Solution Approach 1:
The patent forms etch stop structures at predetermined depths within the alternating stack before forming the memory openings. These pre-positioned etch stop structures act as depth markers that enable single-step or reduced-step etching operations to achieve precise memory opening depths, eliminating the need for multiple sequential etching steps with intermediate measurements and adjustments.
Solution Approach 2:
The etch stop structures are designed to automatically terminate the etching process at the correct depth without requiring external monitoring or control interventions. The etch chemistry is selected to selectively etch through the alternating stack materials while stopping at the etch stop structures, providing self-regulating depth control that reduces manufacturing cycle time while maintaining precision.
3Reliability
If sacrificial materials are used to define memory openings, then structural integrity is maintained during fabrication, but additional removal steps are required
Solution Approach 1:
The patent extracts or removes the sacrificial plugs after they have served their purpose in defining the memory opening positions and creating the etch stop structures. This extraction is performed through selective etching processes that remove the sacrificial material while leaving the etch stop structures and alternating stack intact, enabling subsequent filling operations without the obstruction of sacrificial materials.
Solution Approach 2:
The sacrificial plugs are discarded after their function is fulfilled, but the process is designed to recover value from them by using their removed material or the spaces they created for forming the etch stop structures. The sacrificial plugs enable the creation of precise etch stop structures that improve overall device reliability, making the temporary use and removal of sacrificial materials worthwhile for enhancing final product quality.
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 allows for the efficient fabrication of three-dimensional memory devices with precise etch stop structures, enhancing the manufacturing process and improving the integrity of vertical NAND strings.
Implementation Method 1
forming a second-tier memory opening through the second-tier alternating stack by performing an anisotropic etch process having an etch chemistry that etches materials of the second insulating layers and the second spacer material layers selective to a material of the first conductive material portion
Implementation Method 2
forming a semiconductor plug on a cylindrical sidewall of the etch stop semiconductor material layer over the sacrificial first-tier memory opening fill structure
Data Source
AI summary
A etch stop structure is formed a sacrificial memory opening fill structure formed within a first-tier memory opening vertically extending through a first-tier alternating stack of first insulating layers and first spacer material layers. The etch stop structure may include a conductive etch stop plate that is formed over a sacrificial memory opening fill material portion inside the first-tier memory opening, or may include a semiconductor plug which is selectively grown from sidewalls of an etch stop semiconductor material layer that is formed over the first-tier alternating stack. A second-tier alternating stack of second insulating layers and second spacer material layers is formed over the first-tier alternating stack and the etch stop structure.