Memory Programming Error Detection via Multi-Voltage Off-Cell Counting
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Solution Overview
Problem
Memory devices face challenges in reliably detecting programming errors, particularly due to sudden power-offs during programming operations, which can lead to abnormal threshold voltage distributions and increased reading errors over time.
Innovation Solution
A method is introduced to count and compare the number of memory cells at different reading voltages to determine programming errors, involving a programming error detector with an off-cell counter, comparator, and determiner, which calculates ratios or variations to identify abnormal programming based on predetermined reference values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single reading voltage is used to detect programming errors, then the detection process is simple, but the accuracy of programming error detection is insufficient
Solution Approach 1:
The detection process is segmented into multiple independent reading operations at different reading voltages. The programming error detector counts off-cells at a first reading voltage and compares this count with off-cell counts at a second reading voltage, allowing accurate detection of programming errors by analyzing the relationship between counts from multiple voltage levels rather than relying on a single reading operation
Solution Approach 2:
The system changes the reading voltage parameter to multiple discrete values (first reading voltage and second reading voltage) to detect programming errors. By varying the reading voltage and observing how off-cell counts change across different voltage levels, the system can distinguish between normal wear and actual programming errors, thereby improving detection accuracy without requiring complex additional hardware
2Reliability
If programming errors are not detected, then the memory device operates continuously, but data storage reliability deteriorates over time
Solution Approach 1:
The programming error detector performs preliminary detection of programming errors by counting and comparing off-cell counts at different reading voltages before data becomes corrupted. This preliminary action identifies potentially problematic memory cells early in the wear process, allowing reprogramming to be performed proactively rather than waiting for actual data corruption to occur, thus maintaining reliability while minimizing time loss
Solution Approach 2:
The system implements feedback by continuously monitoring off-cell counts at multiple reading voltages and using this information to determine whether programming errors exist. The comparison results from different voltage levels provide feedback about the health of memory cells, enabling the system to trigger reprogramming operations when degradation patterns indicate impending failures, thereby maintaining data storage reliability
3Reliability
If all memory cells are reprogrammed when errors are detected, then data storage stability is improved, but the productivity of the memory system decreases
Solution Approach 1:
The programming error detector applies local quality by targeting only the specific memory cells or blocks that exhibit error patterns through off-cell count comparisons, rather than reprogramming the entire memory array. When the comparison of off-cell counts at different reading voltages indicates programming errors in a particular region, only that localized region undergoes reprogramming, preserving data storage stability while minimizing the impact on overall system productivity
Solution Approach 2:
The system performs partial reprogramming action by reprogramming only the affected memory blocks identified through error detection rather than performing excessive full-array reprogramming. The programming error detector enables selective reprogramming of specific blocks where off-cell count comparisons indicate errors, achieving sufficient data storage stability improvement without the excessive time cost of reprogramming all memory cells
Data Source
AI summary
A method is provided for operating a memory device. The method includes counting, from among memory cells, a number of first off-cells with respect to a first reading voltage and a number of second off-cells with respect to a second reading voltage, comparing the number of first off-cells and the number of second off-cells, and determining, based on a result of the comparing, whether a programming error exists in a storage region in which the memory cells are included.