Vertical NAND Source Contact Structure for Lower Channel Resistance
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Solution Overview
Problem
The increased resistance associated with the channel structure in semiconductor memory devices, particularly in NAND architectures with a high number of memory cells, poses challenges for efficient operations such as reading, writing, and storing data, as it prolongs the time required for access operations.
Innovation Solution
The implementation of a trench with deposited metal material in contact with a doped polysilicon material of the channel structure reduces the resistance by establishing an electrical coupling between the channel and the source line, thereby enhancing the efficiency of memory device operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the channel structure length is increased to accommodate more memory cells, then the storage capacity is improved, but the resistance increases
Solution Approach 1:
The source contact structure is segmented into multiple portions (first source contact portion, second source contact portion, third source contact portion) that are distributed at different heights along the channel structure. This segmentation allows the source contact to be established at multiple locations, reducing the overall resistance by providing multiple parallel conduction paths rather than a single long path.
Solution Approach 2:
The source contact is extended from a single-plane contact into a three-dimensional structure that contacts the channel at multiple vertical levels. By utilizing the vertical dimension (z-axis) in addition to the horizontal plane, the patent creates multiple contact points along the channel height, effectively reducing resistance without increasing the horizontal footprint.
2Quantity of substance
If the channel structure length is increased to accommodate more memory cells, then the storage capacity is improved, but the access operation time increases
Solution Approach 1:
The source contact is divided into multiple portions positioned at different heights along the channel structure. This segmentation creates multiple parallel current conduction paths, allowing charge to flow through shorter effective paths simultaneously, thereby reducing the overall access operation time despite the increased channel length for higher storage capacity.
3Productivity
If the source contact resistance is decreased by adding metal material, then the operational efficiency is improved, but the device complexity increases
Solution Approach 1:
The patent combines multiple functions into the source contact structure: it serves as both the electrical contact to reduce resistance and as a structural element that integrates with the trench formation process. The metal material is deposited within the trench structure, merging the source contact formation with the existing fabrication steps, thereby reducing operational efficiency losses without proportionally increasing device complexity.
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 effectively decreases the resistance in the channel structure, improving the operational speed and efficiency of memory devices by reducing the time needed for access operations.
Implementation Method 1
deposited metal material in contact with a doped polysilicon material of the channel structure... establishes an electrical coupling between the channel and the source line
Data Source
AI summary
For manufacturing a memory device, a system may form a trench between a first portion and a second portion of a stack. A bottom wall of the trench may include a spacer material. The system may remove a first and a second oxide material to reform the trench, and remove a polysilicon material in a lateral direction to expose a third oxide material and a channel structure. The third oxide material may form the bottom wall of the trench. The system may remove, in a lateral direction, the first oxide material, a portion of the second oxide material, the third oxide material, and a fourth oxide material of the channel structure. The system may deposit a metal material, in the trench, in contact with a doped polysilicon material of the channel structure.