NAND Memory Contact Structure via Inverted Trench Formation
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Solution Overview
Problem
Existing three-dimensional semiconductor memory devices face challenges in manufacturing due to the need for controlling simultaneous multi-step etching processes and forming contact openings with extremely high aspect ratios, which are difficult to achieve, especially as die density increases.
Innovation Solution
A contact structure for 3D semiconductor memory devices is developed, featuring alternating layers of conducting and insulating materials disposed horizontally over a substrate, with a trench formation that allows for electrical connections between layers, eliminating the need for widely varying aspect ratios by exposing continuations of conducting material in a horizontal plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If staircase structures are used to form 3D memory devices, then die density can be increased, but the manufacturing complexity increases due to simultaneous multi-step etching processes and extremely high aspect ratios
Solution Approach 1:
Instead of forming contact openings from the top down through multiple etching steps (staircase approach), the patent forms a single deep trench from the top to the bottom substrate and then fills it with alternating conducting and insulating layers from the bottom up. This inverts the traditional manufacturing sequence, eliminating the need for complex simultaneous multi-step etching processes while achieving the same 3D memory structure.
Solution Approach 2:
The patent performs preliminary trench formation and substrate thinning at the bottom of the trench before depositing the alternating layers. By preparing the trench structure and thinning the substrate in advance, the subsequent layer deposition becomes simpler and more controlled, reducing overall manufacturing complexity while enabling high die density.
2Manufacturing precision
If contact openings with extremely high aspect ratios are formed, then electrical access to deep conducting layers is achieved, but manufacturing precision becomes extremely difficult to control
Solution Approach 1:
Rather than forming narrow contact openings through the entire depth of the structure (top to bottom), the patent forms a single wide trench and fills it with alternating layers. The electrical contacts are then formed to the side walls of the trench at a single depth level, inverting the traditional approach of contacting from the top. This eliminates the need for extremely high aspect ratio contact openings while achieving reliable electrical access to all conducting layers.
3Ease of manufacture
If alternating conducting and insulating layers are deposited, then 3D memory structure is created, but the aspect ratio variation across different layers increases manufacturing difficulty
Solution Approach 1:
The patent segments the trench into multiple sections, each filled with alternating conducting and insulating layers. By dividing the single deep trench into segmented zones with alternating materials, the structure enables electrical contacts to be formed to side walls at different depths, eliminating the need for varying aspect ratios across layers while maintaining ease of manufacture through sequential deposition.
Data Source
AI summary
A NAND-based non-volatile memory contact structure includes a trench located adjacent to layered alternating conducting and insulating layers, the layers lining sides and bottom of the trench. A portion of the trench is removed to expose a surface in which electrical connections to the conducting layers are provided on one level.