Flash Memory Data Conversion for Read Error Reduction

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

In flash memory systems, the E to A phenomenon, where interference between adjacent cells leads to increased threshold voltage and read errors, is exacerbated by micronization and decreased recording prohibition electric potential, making it difficult to maintain the frequency of the erased state distribution.

Innovation Solution

A memory system with a controller that performs data conversions to adjust the ratio of '1' and '0' appearances in each page of a nonvolatile memory, specifically decreasing the frequency of the erased state distribution being surrounded by higher threshold voltage distributions, thereby reducing read errors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If data is written to flash memory cells, then storage capacity is utilized, but interference between adjacent cells increases threshold voltage and causes read errors

Engineering Contradiction:

Improvedata storage capacityVSAvoidread error rate

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies local quality by converting data in specific pages (even or odd pages) differently based on their position. Even pages use one conversion pattern while odd pages use another, creating localized data characteristics that reduce adjacent cell interference. This selective conversion approach targets specific memory regions to minimize the E to A phenomenon while maintaining overall storage capacity.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the data parameters by converting between different representations (e.g., 8B/10B encoding conversions) to alter the distribution of threshold voltages. By modifying the data pattern parameters before writing, the system reduces the frequency of erased state distributions being surrounded by higher threshold voltage distributions, thereby reducing read errors.

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If micronization is applied to increase storage density, then storage capacity increases, but interference between adjacent cells increases causing more read errors

Engineering Contradiction:

Improvestorage densityVSAvoidadjacent cell interference

Core Design Contradiction:

Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

The patent addresses adjacent cell interference in micronized memory by applying different conversion strategies to different pages. This localized approach creates variations in data patterns that reduce the cumulative interference effect between closely spaced cells, allowing higher storage density while mitigating the E to A phenomenon.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent converts the harmful interference effect into a beneficial outcome by using data conversion to create threshold voltage distributions that, while potentially increasing interference in some cases, overall reduce the frequency of problematic erased state patterns. The conversion process transforms raw data into patterns that are less susceptible to adjacent cell interference.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS9865338B2Memory system and method of controlling nonvolatile memory by converting write data written to a page

Publication Date: 2018.01.09 KIOXIA CORP

AI summary

A controller executes a first data conversion for write data to be written into a first page. The first data conversion includes increasing a ratio of a number of a first value to a total number of pieces of data. The controller executes a second data conversion for write data to be written into a second page. The second data conversion includes increasing a ratio of the number of the second value to the total number of pieces of data.