Distributed Row Redundancy in Flash Memory Sectors
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Solution Overview
Problem
Implementing row redundancy in flash memory devices is challenging due to the large die area overhead associated with adding small non-standard physical sectors, which requires additional X-decoders and Y-decoders, limiting the efficiency and feasibility of post-manufacture defect correction.
Innovation Solution
Distributing row redundancy word lines among multiple normal physical sectors, allowing the same decoding and auxiliary circuitry to be used, thereby minimizing die area usage and maintaining robust redundancy without the need for a dedicated redundant sector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dedicated small non-standard physical sector is added for row redundancy, then redundancy capability is improved, but die area increases significantly
Solution Approach 1:
The patent merges the row redundancy functionality with the normal physical sectors by distributing redundant word lines across multiple standard sectors. Instead of creating a separate dedicated redundancy sector, the invention integrates redundancy into the existing sector structure, allowing standard X-decoders and Y-decoders to serve both normal and redundant sectors, thereby eliminating the need for additional decoder area.
Solution Approach 2:
The patent implements multi-functionality by enabling standard physical sectors to serve dual purposes: storing user data and providing row redundancy. The distributed sectors can be configured to replace defective sectors, and the same decoding circuitry serves both normal and redundant functions, maximizing resource utilization without requiring dedicated redundancy infrastructure.
2Ease of operation
If normal size X-decoders and Y-decoders are used for small non-standard physical sector, then decoding functionality is maintained, but die area increases due to redundant decoder requirements
Solution Approach 1:
The patent combines the decoding functions for normal sectors and redundant sectors into a single shared decoder infrastructure. The X-decoders and Y-decoders are designed to handle both normal data sectors and distributed redundancy sectors using the same circuitry, eliminating the need for separate decoder sets and reducing overall die area while maintaining full decoding capability.
3Area of stationary object
If distributed row redundancy is implemented among multiple normal physical sectors, then die area overhead is reduced, but complexity of memory layout increases
Solution Approach 1:
The patent segments the row redundancy functionality across multiple standard physical sectors rather than concentrating it in one dedicated sector. Each standard sector contains a portion of the total redundancy, distributed evenly across the memory array. This segmentation allows the use of standard sector layouts and decoding circuits while achieving the desired redundancy coverage, balancing area efficiency with implementation simplicity.
Data Source
AI summary
A semiconductor device comprises an embedded flash memory with row redundancy. The embedded flash memory comprises a memory bank that includes multiple physical sectors, where each physical sector comprises a plurality of erase sectors. In the memory bank, multiple portions of an additional erase sector are respectively distributed among the multiple physical sectors. The multiple portions of the additional erase sector are configured as a row-redundancy sector for the memory bank.