3D Memory Stack Replacement Insulating Layers With Nitrogen Gradients
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Solution Overview
Problem
Current methods for manufacturing three-dimensional memory devices face challenges in forming efficient replacement insulating layers and achieving high nitrogen concentration gradients in silicon oxynitride layers, which affect the electrical conductivity and memory performance.
Innovation Solution
A method involving the formation of an alternating stack of silicon oxynitride insulating layers and electrically conductive layers, where the silicon oxynitride layers have higher nitrogen concentration at top and bottom surfaces, and the replacement of remaining silicon nitride layers with electrically conductive layers to enhance memory device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods are used to form replacement insulating layers, then the manufacturing process is simpler, but the nitrogen concentration gradient in silicon oxynitride layers is insufficient, affecting memory performance
Solution Approach 1:
The patent applies preliminary action by forming the alternating stack of silicon nitride layers and disposable material layers before the actual replacement process. The silicon nitride layers are prepared in advance with specific thicknesses and patterns, and the disposable material layers are deposited beforehand to enable selective removal. This preliminary preparation allows for precise control of nitrogen concentration gradients in the final insulating layers without adding complexity to the core replacement process.
Solution Approach 2:
The patent implements local quality by creating regions with different nitrogen concentrations within the silicon oxynitride insulating layers. The selective removal of disposable material layers exposes specific portions of silicon nitride layers to oxidation, resulting in insulating layers with spatially varying nitrogen concentrations. This local variation in composition optimizes memory performance by providing different electrical properties in different regions of the same layer.
2Reliability
If selective removal of disposable material layers is performed, then insulating layers with nitrogen concentration gradients are formed, but the process requires additional steps through backside trench formation
Solution Approach 1:
The patent applies dimensionality change by introducing backside trench formation as a new access path from the opposite side of the substrate. Instead of accessing the silicon nitride layers only from the top surface, the backside trenches provide a vertical pathway from below, enabling selective removal of disposable material layers and subsequent oxidation of silicon nitride layers. This additional dimensional approach achieves the desired nitrogen concentration gradients while maintaining manufacturing feasibility.
Solution Approach 2:
The patent uses the disposable material layers as intermediaries that facilitate the formation of insulating layers with nitrogen concentration gradients. These temporary layers are deposited between the silicon nitride layers, serve as masks during selective removal processes, and are later eliminated. The backside trenches act as intermediaries to access and process specific regions of the alternating stack, enabling precise control over the oxidation process and resulting nitrogen distribution.
3Reliability
If remaining silicon nitride layers are replaced with electrically conductive layers, then memory device conductivity is enhanced, but the process complexity increases
Solution Approach 1:
The patent applies the extraction principle by selectively removing the silicon nitride layers from the alternating stack structure. After the disposable material layers are selectively removed and the silicon nitride layers are oxidized to form insulating layers, the remaining silicon nitride layers are extracted and replaced with electrically conductive materials. This selective extraction allows for enhanced electrical conductivity in specific regions while maintaining the insulating properties of the oxidized silicon oxynitride layers, thereby improving memory device performance without requiring complete restructuring of the alternating stack.
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 approach enables the creation of memory devices with improved electrical conductivity and nitrogen concentration gradients, leading to enhanced memory performance and reliability.
Implementation Method 1
oxidizing portions of the silicon nitride layers exposed in the laterally-extending cavities to form insulating layers
Data Source
AI summary
A method of forming a memory device includes forming an alternating stack of disposable material layers and silicon nitride layers over a substrate, forming a memory opening through the alternating stack, forming a memory film in the memory opening, forming a vertical semiconductor channel over the memory film in the memory opening, forming a backside trench through the alternating stack, forming laterally-extending cavities by removing the disposable material layers selective to the silicon nitride layers through the backside trench, oxidizing portions of the silicon nitride layers exposed in the laterally-extending cavities to form insulating layers, and replacing remaining portions of the silicon nitride layers with electrically conductive layers.