3D NAND Stairway Structure Etch Stop Film Design
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Solution Overview
Problem
In semiconductor devices like 3D-NAND nonvolatile storage devices, forming an etch stop film above a metal film to create holes connecting to stairway structures is challenging, as existing methods fail to effectively manage the arrangement of conductive and insulating films.
Innovation Solution
A semiconductor device is designed with a stack structure of alternately disposed insulating and metal films, featuring a stairway portion with terraces, where a liner film and stopper film are used to cover the terraces, and holes are formed through these films to connect to the metal films, utilizing specific etching processes to ensure accurate and reliable contact plug formation with reduced contact resistance variance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an etch stop film is formed above a metal film to create holes connecting to stairway structures, then the reliability of contact plug formation is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent divides the etch stop function into two separate films: a first etch stop film positioned above the metal film and a second etch stop film positioned above the first etch stop film. This segmentation allows each film to be optimized for specific etching processes, improving contact plug formation reliability while managing the complexity through functional specialization rather than requiring a single complex film structure.
Solution Approach 2:
The first etch stop film acts as an intermediary layer between the metal film and the second etch stop film. This intermediary structure enables selective etching processes where the first etch stop film provides a stopping point for etching the metal film, while the second etch stop film provides a stopping point for etching through the first etch stop film, thus mediating the complex multi-layer etching process.
2Manufacturing precision
If multiple etch stop films are used to prevent conductive film shorting, then the manufacturing precision is improved, but the ease of manufacture decreases
Solution Approach 1:
The patent applies different etch stop films at different local positions within the stack structure. The first etch stop film is positioned locally above the metal film where precise contact plug formation is needed, while the second etch stop film is positioned locally above the first etch stop film. Each film has specific local quality characteristics that enable precise control of etching processes at different depths, improving manufacturing precision without requiring uniform complexity throughout the entire structure.
Solution Approach 2:
The first etch stop film is formed preliminarily before the second etch stop film, establishing a foundation for subsequent etching processes. This preliminary action allows the metal film to be etched with precision to the first etch stop film, and then the second etch stop film is added to provide an additional precision stopping point for subsequent etching, thereby improving overall manufacturing precision through staged preparation.
3Adaptability or versatility
If the stairway structure with alternating conductive and insulating films is formed, then the functionality of the semiconductor device is improved, but the difficulty of detecting and measuring the structure increases
Solution Approach 1:
The patent employs etch stop films with distinct visual characteristics that enable easy detection and measurement. The first etch stop film and second etch stop film are designed to have different optical properties or visual identifiers that allow operators to easily distinguish between the different layers during inspection and measurement processes, thereby reducing the difficulty of characterizing the complex stairway structure while maintaining full device functionality.
Data Source
AI summary
A semiconductor device includes a substrate; a stack structure including a plurality of insulating films and a plurality of metal films disposed alternately one above another. The stack structure is provided above the substrate and has a stairway portion including a plurality of terraces located at least at one end portion thereof. A liner film and a stopper film are disposed so as to cover an upper portion the stack structure in the stairway portion formed of the terraces. A plurality of holes are connected to each of the terraces. Each of the terraces is formed of a stack of the insulating films and the metal films. Each of the holes extends through the stopper film and the liner film and connect to the metal films of the terraces.