Word Line Grouping for Read Disturbance Control
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Solution Overview
Problem
The increasing number of word lines per block in semiconductor memory devices leads to varying threshold voltage distributions, causing read disturbances and differing read characteristics, which existing read retry methods struggle to address effectively.
Innovation Solution
A storage apparatus that groups word lines based on similar threshold voltage distributions and applies a representative read voltage to each group, optimizing read performance by adjusting group sizes to meet a set tolerance value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the number of word lines per block is increased to scale down chip size, then chip size is reduced, but read disturbance increases and read characteristics vary
Solution Approach 1:
The patent divides the word lines into multiple groups (first word line group, second word line group, etc.) based on their threshold voltage distributions. Each group is read using a dedicated read voltage level, preventing read disturbance in other groups during the read operation. This segmentation allows increased word line density while maintaining reliable reads through isolated voltage domains.
Solution Approach 2:
Different read voltage levels are applied to different word line groups according to their specific threshold voltage characteristics. The storage controller selectively applies first read voltage to the first word line group and second read voltage to the second word line group, ensuring each group receives optimized read parameters tailored to its local characteristics rather than a uniform approach.
2Area of stationary object
If the number of word lines per block is increased, then chip size is reduced, but read characteristics of word lines become different from each other
Solution Approach 1:
Word lines are segmented into distinct groups based on threshold voltage distribution characteristics. The storage controller maintains separate read voltage levels for each group, allowing each group to be read with optimized parameters that match its specific threshold voltage range, thereby preserving read characteristic uniformity within each group while accommodating overall chip density.
Solution Approach 2:
The patent changes the read voltage parameter according to the threshold voltage distribution of different word line groups. The storage controller adjusts read voltage levels (first read voltage, second read voltage, etc.) based on the specific characteristics of each word line group, enabling adapted read operations that account for variations in threshold voltage across the chip.
3Reliability
If read retry method is used to cope with threshold voltage variation, then read reliability is improved, but read operation complexity increases
Solution Approach 1:
The patent performs preliminary grouping of word lines into distinct groups based on threshold voltage distributions before read operations occur. The storage controller pre-establishes the mapping between word line groups and their corresponding read voltage levels. This preliminary organization eliminates the need for complex real-time threshold voltage detection and adaptive voltage selection during read operations, reducing operational complexity while maintaining reliability.
Solution Approach 2:
The storage controller uses feedback information about threshold voltage distributions to determine which read voltage level to apply to which word line group. By incorporating threshold voltage characteristics into the read operation planning, the system achieves reliable reads without requiring complex iterative retry procedures, as the appropriate voltage is selected based on pre-characterized group properties.
Data Source
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AI summary
A storage apparatus includes a memory device including a plurality of word lines; and a word line grouping device configured to group the plurality of word lines into a certain number of groups each serving as a memory block so that a read performance value, obtained by reading data of word lines included in a same group by using a representative read voltage, is satisfied with a set tolerance value.