Dual Tunnel Oxide Layer Flash Memory Endurance
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Solution Overview
Problem
The existing flash memory architecture with a single-sided tunnel oxide layer affects the operating speed and reduces the endurance and lifespan of the memory, necessitating an improvement in structure and operation method to enhance durability.
Innovation Solution
A semiconductor memory device with two tunnel oxide layers arranged between a floating gate and a substrate, including a select transistor and a floating gate transistor, where the first and second tunnel oxide layers have specific thicknesses and are used for writing and erasing operations, improving the endurance and lifespan of the memory.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-sided tunnel oxide layer is used for writing or erasing operations, then the structure is simpler, but the operating speed decreases and the endurance and lifespan are reduced
Solution Approach 1:
The patent divides the single tunnel oxide layer into two separate tunnel oxide layers (first tunnel oxide layer and second tunnel oxide layer) positioned at different locations. This segmentation allows independent optimization of each layer's thickness and doping configuration, enabling faster electron injection and extraction operations while maintaining structural manageability through modular design
2Device complexity
If a single-sided tunnel oxide layer is used, then the device structure is simpler, but the endurance and lifespan of the memory are reduced
Solution Approach 1:
By segmenting the tunnel oxide structure into two layers with different doping configurations (first tunnel doping region with first conductivity type, second tunnel doping region with second conductivity type), the patent distributes the stress and degradation mechanisms across multiple interfaces, reducing the cumulative damage per operation and extending overall device endurance
Solution Approach 2:
Each tunnel oxide layer is configured with locally optimized properties: the first tunnel oxide layer has specific thickness and doping suitable for write operations, while the second tunnel oxide layer has different parameters optimized for erase operations. This local quality optimization ensures that each layer performs its specific function efficiently without compromising the other, thereby improving reliability
3Speed
If dual tunnel oxide layers with different doping regions are implemented, then the operating speed and endurance are improved, but the device complexity increases
Solution Approach 1:
The patent merges the functions of two separate tunnel oxide structures into a single integrated memory cell design, where both tunnel oxide layers share common elements such as the floating gate, control gate, and substrate connections. This merging approach achieves the performance benefits of dual-layer architecture while reducing the overall device complexity compared to fully independent structures
4Reliability
If dual tunnel oxide layers are used, then the endurance and lifespan are improved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent employs preliminary doping actions where the first and second tunnel doping regions are pre-configured with opposite conductivity types before the tunnel oxide layers are formed. This preliminary preparation simplifies the subsequent manufacturing steps by establishing the electrical characteristics in advance, reducing the complexity of the overall fabrication process while ensuring the desired reliability outcomes
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 dual tunnel oxide layers enhance the operating speed, endurance, and lifespan of the memory device, reducing the need for high-voltage components and lowering production costs while being power-efficient and suitable for embedded applications.
Implementation Method 1
two tunnel oxide layers arranged between a floating gate and a substrate... the first tunnel doping region under the floating gate and between the floating gate oxide layer and the source doping region, a first tunnel oxide layer on the first tunnel doping region
Data Source
AI summary
A semiconductor memory device includes a select transistor and a floating gate transistor on a substrate. The select transistor includes a select gate, a select gate oxide layer and a drain doping region. The floating gate transistor includes a floating gate, a floating gate oxide layer, a source doping region, a first tunnel doping region and a second tunnel doping region under the floating gate, a first tunnel oxide layer on the first tunnel doping region, and a second tunnel oxide layer on the second tunnel doping region. The floating gate oxide layer is disposed between the first tunnel oxide layer and the second tunnel oxide layer. A lightly doped diffusion region surrounds the source doping region and the second tunnel doping region.