Source-Side Programming for 3D NAND Bad Trigger Block Isolation
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Solution Overview
Problem
In 3D NAND flash memory systems, bad blocks can affect other blocks due to electrical dependencies, leading to programming failures, and traditional drain-side programming is inefficient in identifying and addressing these issues.
Innovation Solution
A source-side programming method is introduced, where a detection circuit identifies abnormal threshold voltage distributions on the drain side select gate to mark blocks as bad and apply voltage to word lines via the source side, isolating and correcting bad trigger blocks by blocking leakage paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional drain-side programming is used, then the programming process is simpler, but bad blocks cannot be effectively identified and isolated, leading to programming failures affecting other blocks
Solution Approach 1:
The programming method is segmented into distinct phases: detection phase (identifying bad trigger blocks through threshold voltage measurement), isolation phase (applying specific voltages to block bad blocks from affecting others), and programming phase (normal programming operations). This segmentation allows effective identification and isolation of bad blocks without compromising overall system reliability.
Solution Approach 2:
Before performing normal programming operations, the method performs preliminary detection of threshold voltage distributions on drain side select gates to identify bad trigger blocks. This preliminary action prevents programming failures by isolating problematic blocks in advance, ensuring that subsequent programming operations proceed without interference from bad blocks.
2Reliability
If source-side programming is implemented to isolate bad trigger blocks, then programming reliability improves, but the detection and voltage application process becomes more complex
Solution Approach 1:
The method replaces complex physical inspection or characterization of bad blocks with electrical measurement of threshold voltage distributions. By measuring the electrical property (threshold voltage) of drain side select gates, the system can identify bad trigger blocks through their abnormal electrical characteristics, simplifying the detection process while maintaining high reliability.
Solution Approach 2:
The method utilizes changes in threshold voltage parameters to identify bad trigger blocks. By measuring and comparing threshold voltage distributions against expected ranges, the system can detect anomalies indicating bad blocks. This parameter-based approach provides a quantitative and automated method for block identification and isolation.
3Productivity
If bad blocks are not isolated, then the programming process is faster, but programming failures occur due to electrical dependencies between blocks
Solution Approach 1:
The method extracts or removes bad trigger blocks from the programming process by identifying them through threshold voltage measurement and applying isolation voltages. This extraction prevents bad blocks from participating in subsequent programming operations, eliminating their harmful electrical influence on other blocks while allowing normal programming to proceed efficiently for good blocks.
Solution Approach 2:
The method converts the harmful electrical influence of bad blocks into a detectable signal. By measuring threshold voltage distributions, the abnormal electrical characteristics of bad blocks (which would otherwise cause programming failures) are transformed into useful identification information, allowing the system to isolate and exclude them from affecting other blocks.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively isolates and corrects bad trigger blocks, preventing programming failures by maintaining the source side select gate at 0V and applying voltage from the source side, thereby ensuring accurate data storage and retrieval in 3D NAND flash memory systems.
Implementation Method 1
a detection circuit to detect a threshold voltage distribution on a drain side select gate of a suspected block
Implementation Method 2
applying a voltage to at least one word line of the bad block via a source-side of the memory cell array
Implementation Method 3
maintaining the source side select gate at 0V and applying voltage from the source side
Data Source
AI summary
A source side programming method and system are provided. A bad trigger block, of a plurality of blocks of a memory array, may be detected by determining a threshold voltage distribution of a drain side select gate of a block and determining whether the distribution is abnormal. If the distribution is abnormal, the block is a bad trigger block which may cause a failure in another block. IF the block is a bad trigger block, source side programming is performed on at least one word line of the bad trigger block by applying a non-zero voltage to at least one source side word line of the bad trigger block via a source side line.