Memory Device Read Voltage Offset Extraction
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Solution Overview
Problem
The reliability of memory devices deteriorates due to the widening threshold voltage distribution of memory cells over time, leading to errors in read operations and potential failure of error correction, which affects the overall performance of the memory system.
Innovation Solution
A memory system that generates specific read voltages based on initial voltages and offset voltages to perform read operations on multi-bit memory cells, using a state counter to count data bits and extract the number of memory cells in different threshold voltage regions, thereby maintaining the accuracy of data retrieval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If read operations are performed using initial read voltages, then data can be read from memory cells, but the reliability deteriorates as threshold voltage distribution widens over time
Solution Approach 1:
The patent performs preliminary read operations using initial read voltages to obtain first and second data before the threshold voltage distribution widens significantly. This preliminary action allows the system to capture data states early when the distribution is narrower, improving subsequent extraction accuracy of the threshold voltage distribution characteristics.
Solution Approach 2:
The patent changes the read voltage parameters by applying offset voltages to generate multiple sets of read voltages (first read voltages and second read voltages). By varying the voltage parameters and comparing results across different voltage conditions, the system can accurately extract threshold voltage distribution even as it widens over time.
2Measurement precision
If multiple read voltages with offset voltages are generated and read operations are performed, then threshold voltage distribution can be accurately extracted, but the operation complexity increases
Solution Approach 1:
The voltage generating circuit is designed to universally generate multiple types of read voltages (initial read voltages, first read voltages with first offset, second read voltages with second offset) using the same hardware infrastructure. This multi-functionality allows accurate threshold voltage extraction without requiring separate dedicated circuits for each voltage type, thereby managing complexity.
Solution Approach 2:
The system uses feedback by comparing first data and second data obtained from different read voltage conditions. The memory controller analyzes the differences between these data sets to extract threshold voltage distribution characteristics, creating a feedback mechanism that improves measurement precision while using standard hardware components.
3Duration of action of moving object
If the threshold voltage distribution is allowed to widen naturally over time, then memory operation follows normal degradation, but read operation reliability deteriorates
Solution Approach 1:
The patent performs preliminary read operations and data processing while the threshold voltage distribution is still relatively narrow. By extracting distribution characteristics early in the memory's operational life, the system creates a reference that can be used to maintain reliable read operations even as the distribution widens with continued use and time.
Solution Approach 2:
The system creates a copy or model of the threshold voltage distribution characteristics by analyzing data from multiple read operations. This extracted distribution model serves as a reference that can be used to adjust and maintain read operation reliability throughout the memory's operational duration, compensating for natural degradation.
Data Source
AI summary
There are provided a memory system and an operating method thereof. A memory system includes: a memory device configured to generate first read voltages and second read voltages, based on initial read voltages and first and second offset voltages, in response to a user read command, and output first data and second data, which are acquired by performing read operations on multi-bit memory cells, based on the first read voltages and the second read voltages; and a memory controller configured to output the user read command, wherein the memory controller includes a state counter configured to count numbers of data bits respectively corresponding to a plurality of threshold voltage states from the first data and the second data, and extract numbers of memory cells respectively included in a plurality of threshold voltage regions divided by the first read voltages and the second read voltages by calculating the counted result.