Semiconductor Memory Device Programming Method
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Solution Overview
Problem
Current semiconductor memory devices face challenges in achieving improved program speed and reliability, particularly in maintaining threshold voltage stability during programming operations.
Innovation Solution
The method involves performing a main program operation on memory cells and an additional program operation on cells with changed threshold voltages, using verification voltages and pulses to ensure accurate programming states, and applying program pulses only to cells that require additional programming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a main program operation is performed on all memory cells, then programming coverage is improved, but threshold voltage stability deteriorates due to unnecessary programming of cells that have already reached target states
Solution Approach 1:
The patent implements a feedback mechanism by performing a verification operation after the main program operation to detect memory cells whose threshold voltages have changed. This feedback loop identifies cells that require additional programming while excluding cells that have already achieved the target threshold voltage, thereby resolving the contradiction between comprehensive programming coverage and threshold voltage stability.
Solution Approach 2:
The patent applies partial action by performing additional program operations only on a subset of memory cells that are verified to have changed threshold voltages, rather than re-programming all memory cells. This selective approach maintains productivity while preventing unnecessary threshold voltage changes in already-programmed cells, thus preserving reliability.
2Measurement precision
If verification operations are performed on all memory cells, then programming accuracy is improved, but programming time increases due to verifying cells that do not require additional programming
Solution Approach 1:
The patent applies local quality by performing verification operations with differentiated purposes: a first verification checks for cells requiring additional programming (those with changed threshold voltages), while a second verification confirms successful programming. This localized, targeted verification approach improves programming accuracy for cells that need it while minimizing time spent on cells that are already correctly programmed.
Solution Approach 2:
The verification process is segmented into two distinct stages: first verification to identify cells with changed threshold voltages and second verification to confirm successful programming. This segmentation allows the system to focus verification resources on cells that actually require attention, improving accuracy while reducing overall verification time compared to a uniform verification approach.
3Reliability
If additional program operations are performed on all memory cells, then reliability is improved, but programming speed deteriorates due to redundant operations
Solution Approach 1:
The patent implements partial action by performing additional program operations only on memory cells that are verified to have changed threshold voltages, rather than applying redundant programming to all cells. This selective additional programming maintains reliability by ensuring cells that need re-programming receive it, while preserving speed by avoiding unnecessary operations on cells that have already achieved the target threshold voltage.
4Productivity
If program pulses are applied continuously to all word lines, then programming completeness is improved, but energy consumption increases due to pulsing word lines that do not require additional programming
Solution Approach 1:
The patent applies local quality by controlling program pulse application to be localized to specific word lines corresponding to memory cells that have been verified to require additional programming. Instead of continuously pulsing all word lines, the system selectively applies program pulses only where needed based on verification results, thereby maintaining programming completeness while significantly reducing overall energy consumption.
Data Source
AI summary
A memory device includes a plurality of memory cells each programmed to have any one program state among a plurality of program states divided based on a threshold voltage thereof, and a peripheral circuit for performing a main program operation on the plurality of memory cells, and performing an additional program operation on at least one memory cell of which a threshold voltage regarding the main program operation is changed while the main program operation is being performed.