Flash Memory Data Retention Stabilization via Dummy Write
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Solution Overview
Problem
Flash memory, such as NAND Flash, experiences data retention issues due to floating gate transistors losing electronic charges, leading to increased error bits in data storage, particularly when word lines are not closed.
Innovation Solution
A data maintenance method where a controller writes dummy data into pages controlled by an open word line to stabilize data and reduce error bits by closing the word line, using error correction and read-retry tables to ensure accurate data retrieval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dummy data is written into pages controlled by open word lines to stabilize data, then data retention is improved, but device complexity and operation time increase
Solution Approach 1:
The controller proactively writes dummy data into pages controlled by open word lines before actual data storage operations occur. This preliminary action ensures that word lines are closed and floating gate transistors are stabilized in advance, preventing charge loss and data retention issues before they can affect actual data storage.
Solution Approach 2:
The system performs self-maintenance by automatically detecting open word lines and writing dummy data to close them. The controller monitors the state of word lines and autonomously executes the dummy data writing operation, making the system self-correcting without external intervention.
2Reliability
If dummy data is written into pages controlled by open word lines to stabilize data, then error bits are reduced, but operation time increases
Solution Approach 1:
The controller performs the dummy data writing operation in advance during idle periods or before actual data storage operations. By closing open word lines proactively, the system prevents future read errors without adding time penalties to critical data operations, as the stabilization occurs beforehand.
Solution Approach 2:
The controller continuously monitors the state of word lines and maintains them in a closed state through periodic dummy data writing operations. This continuous maintenance ensures that word lines remain stabilized throughout operation, preventing error bits from accumulating over time while distributing the operation time burden across the entire operational period rather than concentrating it at specific moments.
Data Source
AI summary
A data storage device including a flash memory and a controller. The flash memory includes a plurality of pages and a plurality of word lines, wherein each of the word lines controls at least two of the pages. The controller reads a first page of the pages in response to a read command, wherein the first page is controlled by a first word line of the word lines, and the controller further writes dummy data into the pages controlled by the first word line other than the first page when a predetermined condition is satisfied, wherein the predetermined condition includes that the first word line is not close.