Non-volatile Memory Word Line Programming Sequence for Data Retention
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Solution Overview
Problem
Non-volatile memory devices face challenges in maintaining data reliability due to variations in word line characteristics, particularly in deterioration areas where data retention is compromised, leading to reduced overall system reliability and potential increases in chip size.
Innovation Solution
The implementation of a non-volatile memory device with a memory cell array and a voltage generator, where word lines are categorized into groups based on their deterioration characteristics, with control logic managing program sequences and threshold voltage distributions to minimize interference and enhance data retention, allowing for reduced data bits in deterioration areas without compromising integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If word lines in deterioration areas are used for data storage, then chip size can be reduced, but data reliability deteriorates due to reduced characteristics in deterioration areas
Solution Approach 1:
The patent divides word lines into two groups: a first group where data of at least one bit is written, and a second group where data of at least two bits is written. This segmentation allows different data storage capacities to be assigned to different word line groups, enabling the system to utilize deterioration areas while maintaining data reliability through differentiated usage patterns.
Solution Approach 2:
The patent applies local quality by controlling threshold voltage distributions differently for the first and second word line groups. Specifically, the threshold voltage level corresponding to an erase state of the first group is set higher than that of the second group, creating locally optimized characteristics for each group's specific data storage requirements and deterioration level.
2Quantity of substance
If more data bits are programmed in word lines of deterioration areas, then storage capacity increases, but interference between adjacent word lines increases, further degrading reliability
Solution Approach 1:
The patent implements preliminary action by controlling the program sequence such that word lines of the second group are programmed after adjacent word lines of the first group are programmed. This sequential approach prepares the system state in advance to minimize interference effects during subsequent programming operations, allowing higher storage capacity while maintaining reliability.
Solution Approach 2:
The patent changes parameters by setting different threshold voltage levels for different word line groups. The threshold voltage level corresponding to an erase state of the first group is controlled to be higher than that of the second group, creating distinct electrical characteristics that reduce interference and enable reliable multi-bit storage in the second group.
Data Source
AI summary
A non-volatile memory device includes multiple word lines, and a voltage generator. Some of the word lines correspond to a deterioration area. The voltage generator is configured to generate a program voltage provided to multiple memory cells through the word lines. Control logic implemented by the non-volatile memory device is configured to control a program operation and an erase operation on the word lines. The deterioration area includes word lines of a first group and word lines of a second group. The control logic is configured to control a program sequence so that each of the word lines of the second group is programmed after an adjacent word line of the first group is programmed, and to control a distribution so that a threshold voltage level corresponding to an erase state of each of the word lines of the first group is higher than a threshold voltage level corresponding to an erase state of each of the word lines of the second group.