Memory Controller Invalid Block Pattern Stabilization
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Solution Overview
Problem
Flash memory devices experience reliability issues due to variations in threshold voltages of memory cells over time, leading to data identification problems and decreased storage reliability.
Innovation Solution
A method for a memory controller to detect invalid blocks, determine their state as either charge gain or charge loss, and apply specific invalid patterns to stabilize threshold voltages, thereby improving data reliability by offsetting charge gain or charge loss phenomena.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flash memory devices are used for data storage, then data storage capacity is provided, but threshold voltage variations occur over time causing data identification problems and reliability decrease
Solution Approach 1:
The patent applies preliminary action by performing an invalid pattern operation on invalid blocks before they are reused. This pre-treatment stabilizes the threshold voltages of memory cells in invalid blocks by setting them to a specific invalid pattern (e.g., all 1s or all 0s), preventing future threshold voltage variations that would cause data identification problems when the blocks are subsequently reused for new data storage.
Solution Approach 2:
The patent changes the parameter of threshold voltage distribution by applying an invalid pattern operation that sets memory cells in invalid blocks to a uniform state. This parameter change stabilizes the threshold voltages, creating a known reference state that prevents drift over time and ensures reliable data storage when the blocks are reused.
2Productivity
If memory blocks are reused after becoming invalid, then storage capacity is maintained, but threshold voltage variations cause data identification errors
Solution Approach 1:
Before reusing invalid blocks for new data storage, the patent performs a preliminary invalid pattern operation to stabilize threshold voltages. This ensures that when blocks are reused, they start from a known stable state, preventing data identification errors while maintaining high block reuse efficiency.
Solution Approach 2:
The patent changes the threshold voltage distribution parameter of invalid blocks to a uniform invalid pattern before reuse. This parameter stabilization ensures accurate data identification in subsequently stored data, resolving the contradiction between maintaining productivity through block reuse and ensuring measurement precision for data identification.
3Ease of operation
If no invalid pattern operation is performed on invalid blocks, then operation simplicity is maintained, but threshold voltage variations decrease storage reliability
Solution Approach 1:
The patent implements a self-service mechanism where the memory controller automatically detects invalid blocks and performs invalid pattern operations on them without requiring complex external intervention. This automated process maintains ease of operation while significantly improving data storage reliability by preventing threshold voltage variations.
Solution Approach 2:
The patent uses feedback by detecting the state of memory blocks to identify invalid blocks, then automatically applying invalid pattern operations based on this detection. This closed-loop feedback mechanism ensures reliability improvement through systematic invalid block management while maintaining operational simplicity through automation.
Data Source
AI summary
A method of operating a memory controller, the memory controller configured to control a nonvolatile memory device, the nonvolatile memory device including a plurality of memory blocks. The method including detecting an invalid block among the plurality of memory blocks; determining an invalid pattern based on a state of the invalid block; and performing an operation on the invalid block such that the invalid block has the invalid pattern.