Semiconductor Memory Device Region Segmentation for Data Retention
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Solution Overview
Problem
As semiconductor memory devices become more integrated, their data retention characteristics degrade, leading to reduced refresh periods and the need for increased redundancy cells, which are inefficient, especially as device integration increases.
Innovation Solution
A semiconductor memory device with a cell array divided into regions of different memory characteristics, using a nonvolatile array for storing group information and conversion information to manage memory operations based on these characteristics, allowing for efficient address conversion and refresh management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If device integration is increased, then memory density is improved, but data retention characteristic deteriorates
Solution Approach 1:
The cell array is divided into multiple regions (first region, second region, third region) with different memory characteristics. Each region is managed separately with region-specific refresh periods and replacement policies, allowing the system to optimize for both high density and reliable data retention in different areas simultaneously.
Solution Approach 2:
Different regions of the cell array are assigned different memory characteristics and management strategies. The first region has shorter refresh period, the second region has medium refresh period, and the third region has longer refresh period, creating local optimization for data retention while maintaining high overall density.
2Reliability
If refresh period is reduced, then data retention reliability is improved, but device complexity increases
Solution Approach 1:
The refresh management is segmented into multiple regions with different refresh periods. Instead of implementing a single complex refresh mechanism for the entire array, the system uses simpler region-specific refresh strategies, reducing overall complexity while maintaining reliability.
Solution Approach 2:
The refresh period is made dynamic and adaptive based on region characteristics. The system automatically adjusts refresh timing for each region according to its specific memory characteristics, eliminating the need for complex manual refresh management while ensuring data retention reliability.
3Reliability
If redundancy cells are increased, then reliability is improved, but device complexity increases
Solution Approach 1:
The cell array is segmented into regions with different characteristics, and redundancy cells are strategically placed in specific regions rather than uniformly distributed throughout. This segmented approach reduces the total number of redundancy cells needed while maintaining reliability, and simplifies management by associating redundancy with specific functional regions.
Solution Approach 2:
Redundancy cells are allocated based on local requirements of each region. Regions with more variable or critical memory characteristics receive appropriate levels of redundancy, while regions with stable characteristics have minimal redundancy. This local quality approach improves reliability where needed without unnecessarily increasing overall device complexity.
Data Source
AI summary
A semiconductor memory device includes a cell array including a plurality of regions accessed by first addresses, where the plurality of regions including at least two groups of regions having respectively different memory characteristics. The device further includes a nonvolatile array for nonvolatile storage of group information indicative of which of the least two groups each of the plurality of regions belongs.