Flash Memory Top Oxide Layer Corner Thinning Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Degraded flash memory cell performance due to issues with the top oxide layer, such as 'corner thinning' and poor quality, which affect the reliability and performance of flash memory cells.
Innovation Solution
A semiconductor processing method that forms a tunneling dielectric layer, a charge trapping layer, and a blocking dielectric layer, followed by the formation of trench isolation regions and a polysilicon region, using a sacrificial layer and planarization process to ensure the top oxide layer is of high quality, avoiding exposure of silicon-rich nitride layers that can produce sub-standard oxides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional top oxide layer is formed in flash memory fabrication, then the manufacturing process is simple, but the oxide layer quality degrades due to corner thinning and exposure to silicon-rich nitride layers
Solution Approach 1:
A sacrificial layer is deposited over the silicon-rich nitride layer before forming the top oxide layer. This preliminary action prevents the silicon-rich nitride from degrading the oxide quality by blocking direct exposure, while the sacrificial layer is later removed to restore the original structure.
Solution Approach 2:
The sacrificial layer acts as an intermediary between the silicon-rich nitride layer and the top oxide layer formation process. It temporarily protects the underlying layers during oxide deposition, preventing harmful interactions while allowing the oxide to form with high quality.
2Reliability
If the top oxide layer is formed without protection, then the fabrication process is fast and simple, but corner thinning occurs which degrades memory cell performance
Solution Approach 1:
The sacrificial layer is deposited in advance before the top oxide layer formation. This preliminary protective action prevents corner thinning and performance degradation during oxide deposition, while the additional steps are minimal compared to the benefits gained in reliability.
Solution Approach 2:
The sacrificial layer provides localized protection specifically where needed - over the silicon-rich nitride regions that would otherwise cause corner thinning. This targeted approach improves reliability at critical locations without unnecessarily complicating the entire fabrication process.
3Reliability
If silicon-rich nitride layers are exposed during top oxide formation, then the process is straightforward, but poor quality oxides are produced which reduce flash memory reliability
Solution Approach 1:
The sacrificial layer serves as a mediator that prevents direct interaction between the top oxide formation process and the silicon-rich nitride layer. This intermediary barrier ensures high quality oxide production while adding only minimal complexity to the manufacturing process.
Solution Approach 2:
The process temporarily changes the structural parameters by adding the sacrificial layer, forming the oxide under protected conditions, then removing the sacrificial layer. This parameter change approach ensures oxide quality while maintaining ease of manufacture through straightforward sequential steps.
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 enhances the quality and reliability of the top oxide layer, improving the performance and reliability of flash memory cells by preventing corner thinning and poor quality issues, leading to improved storage density and performance.
Implementation Method 1
Oxidization of the blocking dielectric layer then takes place, which results in the final material for the blocking dielectric layer
Data Source
AI summary
A semiconductor processing method to provide a high quality bottom oxide layer and top oxide layer in a charged-trapping NAND and NOR flash memory. Both the bottom oxide layer and the top oxide layer of NAND and NOR flash memory determines array device performance and reliability. The method describes overcomes the corner thinning issue and the poor top oxide quality that results from the traditional oxidation approach of using pre-deposited silicon-rich nitride.