Curved Charge Storage Elements in 3D NAND Memory
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Solution Overview
Problem
Three-dimensional NAND memory devices with flat memory cells face challenges in optimizing the configuration of tunneling dielectrics with vertical surfaces, which affect the operational voltage and electrical field strengths.
Innovation Solution
The implementation of alternating stacks of electrically conductive strips and air gap strips over a substrate, with memory stack assemblies featuring two-dimensional arrays of lateral protrusion regions, each containing curved charge storage elements and vertical semiconductor channels, enhances electrical field strengths and reduces operational voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If flat memory cells with vertical surfaces are used, then manufacturing is simpler, but electrical field strengths are reduced and operational voltage increases
Solution Approach 1:
The patent applies curvature to the charge storage elements by forming them with lateral protrusion regions that extend outward from the vertical plane of the memory stack. This curved geometry concentrates electrical field lines at the protruding surfaces, enhancing field strength and enabling lower operational voltage while maintaining manufacturing feasibility through standard deposition and etching processes.
Solution Approach 2:
The invention transitions from purely vertical charge storage elements to elements with lateral protrusion regions, adding a horizontal dimension to the charge storage geometry. This dimensional change increases the effective surface area for charge storage and creates regions of concentrated electrical field, improving device performance without complicating the overall stacked architecture.
2Power
If curved charge storage elements are implemented, then electrical field strengths increase and operational voltage decreases, but manufacturing complexity increases
Solution Approach 1:
The curved charge storage elements are formed by segmenting the memory stack into distinct functional regions: alternating conductive strips and air gap strips, with lateral protrusion regions created at specific locations. This segmentation allows each region to be optimized independently while maintaining overall structural integrity and enabling systematic manufacturing approaches.
Solution Approach 2:
The patent implements local quality by creating lateral protrusion regions only at specific locations where charge storage is needed, rather than curving the entire memory stack. The protrusion regions have different geometries and properties than the main vertical channels, allowing optimized electrical field distribution at critical interfaces while maintaining simple vertical structures elsewhere.
3Power
If alternating stacks of conductive strips and air gap strips are used, then electrical field distribution is improved, but device complexity increases
Solution Approach 1:
The patent extracts the charge storage function from the conductive strips and places it in dedicated lateral protrusion regions containing charge storage elements. The conductive strips and air gap strips form alternating stacks that provide electrical field enhancement, while the charge storage elements are separately positioned in protrusion regions, separating field generation from charge storage functions.
Solution Approach 2:
The invention merges multiple functions into the lateral protrusion regions: they serve as both structural elements that define the memory cell boundaries and as locations for charge storage element placement. The protrusion regions combine the benefits of electrical field concentration from the alternating stacks with efficient charge storage in a single integrated structure.
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 configuration enhances electrical field strengths and reduces the required operational voltage for three-dimensional NAND memory devices, improving their performance and efficiency.
Implementation Method 1
each of the lateral protrusion regions comprises a respective curved charge storage element
Data Source
AI summary
A three-dimensional memory device includes alternating stacks of electrically conductive strips and spacer strips located over a substrate and laterally spaced apart among one another by memory stack assemblies. The spacer strips may include air gap strips or insulating strips. Each of the memory stack assemblies includes two two-dimensional arrays of lateral protrusion regions. Each of the lateral protrusion regions comprises a respective curved charge storage element. The charge storage elements may be discrete elements located within a respective lateral protrusion region, or may be a portion of a charge storage material layer that extends vertically over multiple electrically conductive strips. Each of the memory stack assemblies may include two rows of vertical semiconductor channels that laterally overlie a respective vertical stack of charge storage elements.