Memory Array Row Repair via Patch Table and Neighborhood Cache
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Solution Overview
Problem
In memory arrays, data stored in one row can become unreadable due to defects in adjacent rows, especially in antifuse-based memory cells, causing short circuits and rendering previously stored data inaccessible, which existing redundancy mechanisms struggle to address effectively.
Innovation Solution
A method utilizing a patch table to temporarily store data from affected rows, redirecting writes and reads to a repair area, and maintaining a neighborhood cache to manage a moving window of data across rows, ensuring data integrity by remapping addresses and using a direct mapping system to handle defects and errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If data is stored in adjacent rows in a memory array, then storage capacity is improved, but data reliability deteriorates due to short circuits caused by defects in antifuse-based memory cells
Solution Approach 1:
The memory array is segmented into normal data storage area and repair area, with separate address spaces. When a defect is detected in one row, only the affected row and its neighbors are redirected to the repair area, while the rest of the memory array continues to operate normally. This segmentation isolates the impact of defects and maintains overall system reliability.
Solution Approach 2:
A patch table is introduced as an intermediary data structure that stores the mapping relationship between normal row addresses and repair area addresses. This intermediary layer enables transparent redirection of memory access without requiring changes to the memory controller or external interfaces, thus maintaining storage capacity while improving reliability.
2Reliability
If redundancy mechanisms are implemented to repair defective rows, then data reliability is improved, but device complexity increases due to additional repair area and address mapping requirements
Solution Approach 1:
The repair mechanism uses local quality by creating a patch table entry only for the specific defective row and its affected neighbors, rather than allocating entire memory blocks for repair. Each patch table entry contains only the necessary address mapping information for the affected rows, minimizing the overhead and complexity of the redundancy mechanism.
Solution Approach 2:
The system performs preliminary detection of defects during or after programming operations. When a short circuit is detected between adjacent rows, the patch table is updated in advance to redirect future access to the repair area, preventing data corruption before it occurs. This preliminary action approach reduces the need for extensive error correction logic.
3Ease of operation
If a patch table is used to redirect addresses to repair area, then data accessibility is improved for defective rows, but access time increases due to additional address mapping lookups
Solution Approach 1:
The address mapping functionality is extracted from the main memory access path and implemented as a separate patch table lookup operation. This extraction allows the majority of memory accesses to proceed directly without additional overhead, while only accesses to defective rows require patch table consultation. The repair area itself is designed to provide fast access, minimizing the time penalty for redirected operations.
Data Source
AI summary
A method for repairing a neighborhood of rows in a memory array using a patch table is disclosed. First data to be stored in row N in a memory array of the memory device, second data, if any, stored in row N−1 in the memory array, and third data, if any, stored in row N+1 in the memory array are stored in a temporary storage area of a memory device. The first data is written in row N, and, in response to an error, the first data, the second data, if any, and the third data, if any, are written in respective rows in a repair area in the memory device. The addresses of rows N−1, N, and N+1 are added to a table stored in the memory device to indicate which rows in the repair area should be used instead of rows N−1, N, and N+1.