Error Corrected Pre-Read for Upper Page Write in MLC Memory
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Solution Overview
Problem
In multi-level cell (MLC) flash memory, traditional programming methods often increase the voltage threshold of flash cells, which can erase other cells and are inefficient, especially when trying to program upper pages without correctly reading and correcting errors in lower pages, leading to slower read operations and potential errors.
Innovation Solution
A method is introduced to program MLCs by setting the voltage threshold based on both the first and second pages of data, allowing for efficient storage and correction of data without reading the MLC between the program request and programming, using error correction codes and specific voltage ranges to define different states, thereby optimizing programming operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional programming methods are used to program upper pages in MLC, then the voltage threshold is increased, but this erases other cells and reduces reliability
Solution Approach 1:
The patent applies parameter changes by using different voltage thresholds for programming upper pages versus lower pages. Instead of using a single high voltage threshold that erases cells, the system uses a lower voltage threshold for upper page programming while maintaining a separate threshold for lower page programming. This resolves the contradiction by changing the voltage parameter to avoid unintended cell erasure while maintaining programming efficiency.
2Reliability
If MLC programming requires reading and correcting errors in lower pages before programming upper pages, then data accuracy is improved, but read operation speed decreases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing error correction codes during the programming process itself. The system calculates ECC for both lower and upper pages during the programming operation, so that when reading occurs later, the correction data is already prepared and associated with the data, eliminating the need for time-consuming read-verify-correct cycles and thus improving read speed while maintaining accuracy.
3Quantity of substance
If multiple pages are programmed simultaneously in MLC, then storage density is improved, but error correction complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the error correction process into separate, manageable segments - one for lower page data and one for upper page data. Each page is processed independently with its own error correction codes, rather than attempting to correct errors across the entire multi-page structure simultaneously. This segmentation reduces the complexity of error correction while maintaining the ability to program multiple pages simultaneously for high storage density.
Data Source
AI summary
Methods, apparatuses and articles of manufacture may receive a first page of data and correct one or more errors in the first page of data to generate a page of corrected data. A program command may then be sent with a second page of data and the page of corrected data, to program a page of memory to store the second page of data.