Nonvolatile Memory Over-Program Verification and ECC Correction
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Solution Overview
Problem
The reliability of programming operations in nonvolatile memory devices is compromised due to irregular increases in threshold voltages of memory cells, leading to over-programmed cells that can interfere with neighboring cells, causing incorrect data readouts.
Innovation Solution
A method that involves inputting program data into page buffers, performing program operations with incremental step pulse programming, and including over-program verification to identify and correct over-programmed cells, ensuring threshold voltages reach target levels while enabling error checking and correction processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If incremental step pulse programming is used to raise threshold voltages, then programming speed is improved, but threshold voltage irregularity increases causing over-programmed cells
Solution Approach 1:
The patent applies preliminary action by performing an over-program verification operation after the main program operation to identify and correct cells that have been over-programmed. This preliminary check prevents data corruption before it occurs during subsequent read operations, resolving the contradiction by maintaining both programming speed and threshold voltage precision.
Solution Approach 2:
The patent implements feedback through the over-program verification operation that checks threshold voltages after programming and provides correction information back to the system. This feedback mechanism allows the system to identify over-programmed cells and apply corrections, thereby maintaining precision while preserving the speed benefits of incremental step pulse programming.
2Productivity
If program voltage level is increased to raise threshold voltages, then programming efficiency is improved, but threshold voltage irregularity increases
Solution Approach 1:
The over-program verification operation serves as a preliminary action that identifies cells with irregular threshold voltage increases before they cause reliability issues. By detecting over-programmed cells early and applying corrections, the system maintains both programming efficiency and operational reliability.
Solution Approach 2:
The verification operation provides feedback on threshold voltage distribution, allowing the system to identify and correct irregularities caused by high program voltage application. This feedback loop ensures that programming efficiency gains do not compromise reliability.
3Measurement precision
If over-program verification operation is added to identify over-programmed cells, then data accuracy is improved, but operation time increases
Solution Approach 1:
The over-program verification operation applies partial action by focusing only on detecting over-programmed cells rather than verifying every cell in detail. This selective verification approach maintains high measurement precision for threshold voltages while minimizing the time penalty, as the verification targets only the problematic subset of cells.
Data Source
AI summary
A method of programming a nonvolatile memory device includes inputting program data to page buffers; performing a program operation and a program verification operation until threshold voltages of memory cells included in a selected page reach a target level according to the program data; when the threshold voltages of the memory cells reach the target level, performing an over-program verification operation to determine over-programmed memory cells in the memory cells; and making a determination of whether error checking and correction (ECC) processing for the over-programmed memory cells is feasible.