Fatal Wordline Leak Detection for Selective Block Retirement
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Solution Overview
Problem
Existing storage systems face challenges in detecting and managing fatal wordline leakage, which can lead to global fail and preemptive die retirement, causing performance degradation and unnecessary overprovisioning loss.
Innovation Solution
The implementation of a fatal wordline leak detection (F-WLLD) mode that accurately identifies potential CGI shorts, allowing for proactive retirement of affected blocks without retiring the entire die, thereby preventing fatal plane/die-level data loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If built-in self-test leak detection modes are used to screen-out leaky blocks, then data loss is limited to a few pages, but the system cannot detect fatal wordline leakage that leads to global fail
Solution Approach 1:
The patent applies preliminary action by performing enhanced leak detection during factory test before the product is shipped. The F-WLLD mode is activated during manufacturing to proactively identify fatal wordline leakage issues, allowing defective blocks to be marked as factory bad blocks before they cause problems in the field. This prevents future data loss and eliminates the need for complex runtime detection mechanisms.
2Reliability
If preemptive die retirement is performed to prevent global fail, then data loss is prevented, but performance degrades and overprovisioning capacity is lost
Solution Approach 1:
The patent applies segmentation by dividing the memory die into individual blocks and enabling selective retirement of only the affected blocks rather than the entire die. When F-WLLD detects a fatal wordline leakage in a specific block, the system marks only that block as a grown bad block and retires it, while leaving the rest of the die operational. This segmented approach maintains system performance and preserves overprovisioning capacity in other healthy blocks.
Solution Approach 2:
The patent implements feedback through continuous monitoring of block status during factory test and field operation. The F-WLLD mode provides real-time feedback on wordline leakage conditions, allowing the system to dynamically adjust block retirement decisions based on actual leakage detection results. This feedback mechanism ensures that only truly defective blocks are retired, preventing unnecessary performance degradation.
3Reliability
If entire die is retired instead of affected blocks, then global fail is prevented, but overprovisioning capacity is wasted
Solution Approach 1:
The patent applies segmentation by treating each block as an independent retireable unit rather than retiring the entire die. The F-WLLD detection mechanism identifies specific affected blocks, and the system then selectively retires only those blocks while preserving the rest of the die's overprovisioning capacity for future use. This eliminates the waste associated with blanket die retirement.
Solution Approach 2:
The patent applies discarding and recovering by selectively discarding (retiring) only the defective blocks that have been identified through F-WLLD detection, while recovering and retaining the healthy blocks and their overprovisioning capacity. This selective approach ensures that valuable overprovisioning resources are not wasted on dies that can still function with minor block retirements.
Data Source
AI summary
In some situations, a leak on a wordline may be a localized problem that causes data loss in a block that contains the wordline. In other situations, such as when the leak occurs near a peripheral wordline routing area, the leak can affect the entire memory die. The storage system provided herein has a fatal wordline leak detector that determines the type of leak and, accordingly, whether just the block should be retired or whether related blocks should be retired.