Memory Controller String Defect Leakage Check for 3D NAND Shorts
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Solution Overview
Problem
In three-dimensional memory architectures, large block sizes lead to select gate drain (SGD) to slit half etch (SHE) shorts, impacting string operations due to process or lithographic issues, which existing technologies fail to effectively resolve.
Innovation Solution
A memory controller with a memory interface and controller circuit that performs a string defect leakage check during programming operations to identify and resolve string to string shorts, allowing partial use of impacted memory blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If large block size is used in three-dimensional memory architectures, then manufacturing efficiency and storage capacity are improved, but string to string shorts occur due to process or lithographic issues
Solution Approach 1:
The patent performs a string defect leakage check during the first programming operation of a memory block to proactively detect string to string shorts before they impact normal operations. By identifying defective strings early in the programming process, the system can resolve these defects through additional programming pulses or voltage adjustments, preventing reliability issues before they manifest during regular read/write operations.
Solution Approach 2:
The patent implements a feedback mechanism where the controller monitors leakage current during programming operations and uses this information to identify and resolve string to string shorts. The system continuously checks for defects and adjusts programming parameters accordingly, creating a closed-loop control system that improves reliability while maintaining large block sizes for manufacturing efficiency.
2Reliability
If string to string shorts are detected, then memory block reliability is improved, but available memory capacity is reduced due to block retirement
Solution Approach 1:
The patent performs string defect leakage checks during the first programming operation to identify string to string shorts before the memory block is fully operational. By detecting and resolving these defects early, the system prevents the need to retire entire memory blocks, thereby maintaining maximum available memory capacity while ensuring reliability.
Solution Approach 2:
Instead of retiring memory blocks with string to string shorts, the patent recovers these blocks by resolving the shorts through additional programming operations. The system identifies defective strings, applies corrective programming pulses, and validates the resolution, thereby recovering the memory capacity that would otherwise be lost to block retirement.
3Reliability
If string defect leakage check is performed during first programming operation, then string to string shorts are identified early, but programming time is increased
Solution Approach 1:
The patent merges the string defect leakage check with the first programming operation of the memory block. By integrating the defect detection process into the existing programming sequence rather than adding a separate verification step, the system achieves reliable defect identification without significant increases in overall programming time. The leakage check is performed concurrently with or immediately during the initial programming pulses.
Data Source
AI summary
A memory controller includes, in one embodiment, a memory interface and a controller circuit. The memory interface is configured to interface with a memory interface configured to interface with a memory having a plurality of memory blocks. Each memory block has a plurality of strings. The controller circuit is configured to perform a string defect leakage check on one of the memory blocks during a first programming operation of the one memory block, determine whether the one memory block has one or more string to string shorts based on the string defect leakage check, and resolve the string to string shorts in response to determining that the one of the memory blocks has the string to string shorts.