Flag Cell Programming with Dummy Cells to Suppress Disturbance
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Solution Overview
Problem
Nonvolatile semiconductor memory devices face challenges in maintaining the threshold voltage of flag cells due to program disturbance and charge loss, leading to potential read errors, especially when adjacent cells are not properly managed during programming operations.
Innovation Solution
The implementation of a nonvolatile memory device with flag cells and dummy cells, where the program control logic controls the programming operations using an ISPP scheme, omitting verification read operations for dummy cells, and adjusting voltage levels to prevent unintended changes in threshold voltages, with dummy cells being programmed to specific levels to stabilize flag cell voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If verification read operations are performed on dummy cells to ensure proper programming, then programming accuracy is improved, but operation time and complexity increase
Solution Approach 1:
The patent extracts the verification read operation from the dummy cell programming process. Since dummy cells are only used to suppress program disturbance and not to store actual data, the patent removes the verification step that would be necessary for regular memory cells, thereby reducing operation time and complexity while maintaining programming accuracy for flag cells.
Solution Approach 2:
The patent treats dummy cells as disposable elements that serve a temporary protective function during programming. These cells are programmed solely to suppress program disturbance and do not require verification or long-term data integrity, allowing the system to use simpler, faster programming without verification reads.
2Stability of the object's composition
If dummy cells are programmed to the same voltage level as flag cells, then program uniformity is improved, but program disturbance increases
Solution Approach 1:
The patent applies different voltage levels to different cell types based on their specific functions. Flag cells receive higher programming voltages to ensure proper data storage, while dummy cells receive lower programming voltages sufficient only for suppressing program disturbance. This localized differentiation of programming parameters prevents program disturbance while maintaining the necessary uniformity for each cell type's function.
3Reliability
If flag cells are programmed with high voltage to ensure data retention, then reliability is improved, but adjacent dummy cells experience program disturbance
Solution Approach 1:
The patent applies preliminary anti-action by programming dummy cells to a specific voltage level before flag cell programming to create a protective barrier. The dummy cells are pre-programmed to a voltage that suppresses program disturbance, effectively counteracting the harmful effects that would otherwise propagate from high-voltage flag cell programming to adjacent cells.
Solution Approach 2:
The patent introduces dummy cells as intermediary elements between programming operations and flag cells. These dummy cells act as mediators that absorb and suppress the program disturbance generated during flag cell programming, protecting the overall memory structure from voltage-induced interference while allowing reliable data retention in flag cells.
Data Source
AI summary
A nonvolatile memory device includes a flag cell configured to store flag information, a plurality of dummy cells adjacent to the flag cell, and program control logic configured to control a program operation on the flag cell and a dummy program operation on the plurality of dummy cells. When the program operation on the flag cell is performed, the program control logic performs the dummy program operation on at least one of the plurality of dummy cells.