Weak Word Line Access Using Selective Read and Write Modes
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Solution Overview
Problem
Memory systems with weak word lines experience higher bit error rates and charge loss, leading to increased costs and system complexity due to the need for additional error correction capabilities.
Innovation Solution
The memory system identifies weak word lines during manufacturing and adjusts programming and reading operations accordingly, using extended programming times for writes and high reliability decoding for reads to improve endurance without additional error correction capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional error correction capabilities are added to handle weak word lines, then reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies preliminary action by identifying weak word lines during manufacturing testing and recording their locations in a lookup table before the memory device is deployed. This advance identification allows the system to proactively compensate for weak word lines through adjusted read operations, eliminating the need for complex real-time error correction hardware and reducing overall system complexity while maintaining reliability
2Reliability
If additional error correction capabilities are added to handle weak word lines, then reliability is improved, but cost increases
Solution Approach 1:
The patent uses copying by creating a lookup table that stores the locations of weak word lines identified during manufacturing. This table acts as a simplified copy or map of the physical memory structure, allowing the system to navigate around weak word lines using simple address adjustments rather than implementing expensive complex error correction circuitry, thereby reducing manufacturing costs while maintaining reliability
3Reliability
If extended programming times are used for weak word lines, then reliability is improved, but productivity decreases
Solution Approach 1:
The patent applies local quality by implementing differentiated programming strategies tailored to specific weak word lines identified during manufacturing. Instead of uniformly extending programming time for all word lines, the system selectively applies extended programming only to identified weak word lines, thereby improving their reliability while minimizing the impact on overall programming productivity
4Reliability
If high reliability decoding is used for reading weak word lines, then reliability is improved, but response time increases
Solution Approach 1:
The patent applies local quality by implementing differentiated read strategies for weak word lines versus normal word lines. The system uses high reliability decoding selectively only for weak word lines identified in the lookup table, while using standard faster decoding for normal word lines. This localized approach improves read accuracy for problematic lines without significantly impacting overall system response time
Data Source
AI summary
Methods, systems, and devices for access operations on weak word lines are described. A memory system may receive a command and may determine that the command is associated with a word line having a characteristic that satisfies a threshold value. If the command is a first type, such as a programming command (e.g., a write command), the memory system may perform the programming command using a first type of write operation (of a plurality of types of write operations). If the command is a second type, such as a read operation, the memory system may perform the read operation using a first type of read operation (of a plurality of types of read operations).