3D NAND Trench Fill Structure for Reduced Wafer Bowing
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Solution Overview
Problem
Existing methods for fabricating three-dimensional NAND devices face challenges in managing mechanical stress imposed by control gate electrodes and trench materials, leading to substrate warpage, which can affect device reliability and performance.
Innovation Solution
A monolithic three-dimensional NAND device structure is developed, featuring alternating layers of first and second trench materials with different stress types, where the second trench material is used to offset the stress imposed by the first trench material and control gate electrodes, thereby reducing substrate warpage. This is achieved by etching a trench in the stack of alternating layers, filling it with the first trench material, and inserting an electrically insulating material between the first and second trench materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If control gate electrodes and trench materials are deposited to form three-dimensional NAND device structures, then device density and functionality are improved, but substrate warpage occurs due to accumulated mechanical stress
Solution Approach 1:
The patent applies composite materials by combining multiple trench fill materials with different stress characteristics (first trench fill material with compressive stress, second trench fill material with tensile stress) to create a balanced structure that maintains substrate flatness while enabling high-density three-dimensional NAND device formation
Solution Approach 2:
The patent changes the stress parameter of trench fill materials by selecting materials with opposite stress types (compressive and tensile) to counterbalance each other, thereby controlling substrate warpage while maintaining device functionality and density
2Ease of manufacture
If single-material trench filling is used to simplify fabrication, then manufacturing complexity is reduced, but substrate warpage cannot be effectively controlled
Solution Approach 1:
The patent applies local quality by assigning different stress characteristics to different regions of the trench fill structure, where the first trench fill material provides compressive stress in certain regions and the second trench fill material provides tensile stress in other regions, enabling localized stress management to maintain overall substrate flatness
3Manufacturing precision
If alternating layers of materials with different stress types are deposited, then substrate warpage is reduced through stress offset, but device structure complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the trench fill structure into distinct layers of first trench fill material and second trench fill material, where each layer is deposited separately and provides specific stress characteristics, enabling controlled stress management while maintaining a systematic fabrication process
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 approach effectively reduces substrate warpage and enhances the reliability of the NAND device by mitigating the mechanical stress caused by the trench materials and control gate electrodes, allowing for more efficient and stable fabrication of high-density memory arrays.
Implementation Method 1
The first trench material comprises a material under a first magnitude of a first stress type, and the second trench material comprises a material under no stress, a second stress type opposite the first stress type, or a second magnitude of the first stress type lower than the first magnitude of the first stress type to offset warpage of the substrate due to the stress imposed by at least one of the first trench material or the plurality of control gate electrodes on the substrate
Data Source
Figure 1A~1C
Figure 2A~2C
Figure 3A~3D
AI summary
A monolithic three dimensional NAND string includes a plurality of control gate electrodes extending substantially parallel to a major surface of a substrate, and at least one trench extending substantially perpendicular to the major surface of the substrate. The trench is filled with at least a first trench material and a second trench material. The first trench material includes a material under a first magnitude of a first stress type, and the second trench material includes a material under no stress, a second stress type opposite the first stress type, or a second magnitude of the first stress type lower than the first magnitude of the first stress type to offset warpage of the substrate due to the stress imposed by at least one of the first trench material or the plurality of control gate electrodes on the substrate.