Composite Hard Mask Etching Profile for High-Aspect-Ratio Trenches
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-aspect-ratio trenches in semiconductor fabrication are prone to distortion, bending, and collapse during wet strip processing due to capillary forces, leading to voids when filled with polysilicon, which affects integrated circuit performance and increases manufacturing costs.
Innovation Solution
A method involving a semiconductor film stack with a hard mask layer, alternating oxide/polysilicon layers, and a silicon nitride layer, where an OP etch forms high-aspect-ratio trenches, followed by trimming to create a pencil-like bit line profile, reducing surface tension and preventing trench collapse, and facilitating fill-in with polysilicon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wet strip processing is used to remove polymer residue, then cleaning effectiveness is improved, but trench collapse occurs due to capillary forces
Solution Approach 1:
The patent applies preliminary action by forming a tapered hard mask profile before wet strip processing. The etch process creates a gradual taper in the hard mask layer that provides structural support to the trench walls during subsequent wet strip cleaning, preventing collapse while allowing effective polymer removal.
Solution Approach 2:
The patent uses composite materials by combining the hard mask layer with the underlying trench structure. The hard mask material forms a composite structural element with the trench walls, creating a reinforced profile that resists capillary forces during wet strip processing while maintaining cleaning effectiveness.
2Length of moving object
If conventional etching is used to form high-aspect-ratio trenches, then trench depth is achieved, but trench profile distortion and bowing occur
Solution Approach 1:
The patent applies local quality by creating a non-uniform hard mask profile with different geometries at different locations. The tapered profile provides wider support at the trench opening and gradually narrows toward the bottom, providing location-specific structural reinforcement that prevents profile distortion and bowing while maintaining high aspect ratio.
Solution Approach 2:
The patent uses parameter changes by modifying the hard mask profile geometry through controlled etching parameters. The etch process parameters are optimized to create a specific tapered profile shape that maintains structural integrity during fabrication, preventing distortion and bowing while achieving the required trench depth.
3Length of moving object
If trench width is reduced to achieve smaller critical dimensions, then device scaling is improved, but trench collapse becomes more likely
Solution Approach 1:
The patent uses composite materials by forming a tapered hard mask structure that acts as a composite reinforcement with the trench walls. This composite profile provides enhanced structural support that enables smaller trench widths while maintaining stability against collapse.
Solution Approach 2:
The patent applies preliminary action by pre-forming the tapered hard mask profile before trench narrowing. This preliminary structural reinforcement allows subsequent processing to achieve smaller critical dimensions while the established tapered profile continues to provide collapse prevention support.
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 method effectively inhibits trench collapse and bowing, ensuring accurate trench profiles and reducing void formation during fill-in, thereby enhancing integrated circuit performance and yield without altering conventional wet strip processes.
Implementation Method 1
A critical dimension (CD) trim operation is performed whereby exposed portions of the SIN layer are etched by plasma
Implementation Method 2
Post-etch investigation has confirmed that such bending typically does not occur prior to, bur rather occurs at the time of, wet-strip processing during prior art manufacturing. This observation tends to confirm that the bending is caused by capillary forces on trench side walls that occur during the wet strip processing.
Data Source
AI summary
High-aspect ratio trenches in integrated circuits are fabricated of composite materials and with trench boundaries having pencil-like etching profiles. The fabrication methods reduce surface tension between trench boundaries and fluids applied during manufacture, thereby avoiding pattern bending, bowing, and collapse. The method, further, facilitates fill-in of trenches with suitable selected materials.