Semiconductor Memory Device Foggy-Fine Programming Method
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Solution Overview
Problem
Semiconductor memory devices face challenges in reliably programming and verifying data due to interference phenomena in three-dimensional memory cell arrays, leading to issues with data integrity and reliability during program operations.
Innovation Solution
The implementation of a foggy-fine programming method, which includes foggy programming to temporarily change threshold voltage distributions to intermediate states and fine programming using specific verify voltages to achieve target program states, improving data reliability by separating memory cells into distinct groups for separate voltage applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If three-dimensional memory cell arrays are used to increase storage capacity, then storage density is improved, but interference phenomena occur between adjacent memory cells leading to reduced data reliability
Solution Approach 1:
The patent segments the programming process into two distinct phases: foggy programming that programs all selected memory cells to an intermediate threshold voltage state, and fine programming that selectively adjusts individual memory cells to their final target states. This segmentation allows cells to be programmed in groups first, then individually refined, reducing interference between adjacent cells while maintaining high storage density in three-dimensional arrays.
Solution Approach 2:
The foggy programming step serves as a preliminary action that pre-programs all selected memory cells to an intermediate state before the fine programming step refines them to final states. This preliminary programming establishes a baseline state that simplifies subsequent verification and adjustment operations, improving overall programming reliability in dense three-dimensional structures.
2Manufacturing precision
If multiple verify voltages are used to accurately program memory cells to target states, then manufacturing precision is improved, but the programming process complexity increases
Solution Approach 1:
The verification process is segmented into two stages corresponding to the two programming phases. During foggy programming, a first verify voltage checks if memory cells have reached the intermediate threshold voltage state. During fine programming, a second verify voltage checks if cells have reached their final target states. This segmentation simplifies verification by using distinct voltage thresholds for distinct programming stages, improving precision without overwhelming complexity.
Solution Approach 2:
The patent changes the verify voltage parameter between programming stages. A first verify voltage is used during foggy programming to verify intermediate states, and a second verify voltage is used during fine programming to verify final target states. This parameter change adapts the verification process to the specific requirements of each programming phase, ensuring accurate programming while maintaining process manageability.
3Productivity
If foggy programming is performed first to set intermediate states, then fine programming can be performed more efficiently, but the total programming time increases
Solution Approach 1:
The programming process is segmented into foggy programming and fine programming phases that can be executed in parallel across different memory cell groups. While some cells undergo fine programming adjustments, other cells may already be in their final states from the foggy programming phase, allowing overlapping execution and reducing overall time penalty.
Solution Approach 2:
The foggy programming step programs all selected memory cells to an intermediate state, which is more than the minimal action required for final programming. However, this excessive action benefits subsequent fine programming operations by establishing uniform intermediate states that require smaller adjustments to reach final states, improving overall efficiency despite the additional initial programming step.
Data Source
AI summary
A method of operating a semiconductor memory device programming selected memory cells to store bits of data in each of the selected memory cells includes foggy programming and fine programming.