Semiconductor Memory Device Foggy-Fine Programming Scheme
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Solution Overview
Problem
Existing semiconductor memory devices face challenges in ensuring reliable operation, particularly during programming operations, due to issues with data verification and voltage control, which can lead to errors and reduced reliability.
Innovation Solution
The implementation of a foggy-fine programming scheme, where memory cells are programmed using different verify voltages and voltages applied to bit lines, allowing for precise control of threshold voltages and initiating the flag cell programming only after completing the foggy programming operation, enhances operational reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single programming operation is used for all memory cells, then the programming process is simple and fast, but the reliability and accuracy of data programming are reduced
Solution Approach 1:
The programming operation is divided into two distinct segments: foggy programming for general memory cells and fine programming for flag cells. This segmentation allows each type of cell to receive appropriately optimized programming parameters, improving overall reliability while maintaining manageable complexity through systematic division of the programming process.
Solution Approach 2:
Different programming parameters (verify voltages, program pulses, bit line voltages) are applied to different locations within the memory array. General memory cells receive one set of programming parameters while flag cells receive another set, allowing local optimization for each cell type's specific requirements and improving programming accuracy.
2Reliability
If flag cell programming is performed simultaneously with memory cell programming, then the programming process is completed faster, but programming errors increase and reliability decreases
Solution Approach 1:
Foggy programming is performed as a preliminary action on general memory cells before fine programming is applied to flag cells. This preliminary programming establishes a foundation that reduces interference during subsequent flag cell programming, improving accuracy while the sequential nature minimizes time loss through efficient parameter optimization.
Solution Approach 2:
The programming process uses periodic verification operations with different verify voltages for foggy and fine programming phases. This periodic verification ensures accurate programming at each stage while maintaining a structured rhythm that prevents errors and improves reliability without excessive time consumption.
3Measurement precision
If high verify voltages are used for all memory cells, then programming accuracy is improved, but energy consumption increases and device stress increases
Solution Approach 1:
Different verify voltage levels are applied to different locations: higher verify voltages are used for flag cells to ensure accurate detection of programming state, while lower verify voltages suffice for general memory cells. This local differentiation maintains necessary accuracy while reducing overall energy consumption and device stress.
Solution Approach 2:
The verify voltage parameter is dynamically changed between foggy programming phase (lower verify voltages) and fine programming phase (higher verify voltages for flag cells). This parameter adaptation ensures sufficient verification accuracy at each stage while optimizing energy consumption by using higher voltages only when absolutely necessary.
4Reliability
If programming operations are performed without differentiated voltage control, then the control circuit is simpler, but programming errors increase particularly during sudden power-offs
Solution Approach 1:
The voltage control is segmented into distinct control schemes for foggy programming and fine programming. This segmentation creates a modular control structure that improves error resistance through systematic voltage management while keeping circuit complexity manageable by organizing control logic into distinct, reusable modules for each programming phase.
Solution Approach 2:
Foggy programming with its specific voltage control scheme is performed as a preliminary action that prepares memory cells in a stable state before fine programming. This preliminary voltage control establishes conditions that reduce susceptibility to power-off errors during subsequent operations, improving reliability while the structured approach keeps control circuit complexity manageable.
Data Source
AI summary
Provided herein may be a method of operating a semiconductor memory device. The method of operating a semiconductor memory device may include programming selected memory cells with first page data, and programming the selected memory cells with second page data and programming a flag cell with flag data according to a foggy-fine programming scheme. The flag data may indicate whether data programmed according to the program operation is the first page data or the second page data. An operation of programming the flag cell with the flag data may be initiated after foggy programming of the second page data is completed.