Flash Memory Programming Method for Reducing 2-Bit Errors

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Multi-bit flash memory devices face challenges with charge loss and over-programming, leading to 2-bit errors due to dense threshold voltage distributions, which increase the load on memory devices and error correction processes.

Innovation Solution

A programming method that selectively changes threshold voltage distributions by programming memory cells to a voltage higher than the verify voltage, with the verify voltage being either within or higher than the initial distribution, to reduce program errors and adjust voltage intervals between distributions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If multi-bit flash memory cells are programmed densely to include 2^k threshold voltage states within the limited threshold voltage range, then the storage capacity is improved, but the read margin between threshold voltage states is reduced

Engineering Contradiction:

Improvestorage capacityVSAvoidread margin

Core Design Contradiction:

Quantity of substanceVSMeasurement precision

Solution Approach 1:

The patent segments the programming process into multiple stages, programming different pages of data sequentially. Each page programming operation targets specific threshold voltage distributions, allowing the system to manage dense threshold voltage states in a controlled manner while maintaining adequate read margins through staged verification

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent performs preliminary programming of earlier pages before programming subsequent pages. By establishing threshold voltage distributions from previous pages first, the system creates a foundation that allows later pages to be programmed into adjacent distributions without causing errors, even when distributions are densely packed

Inventive Principle:

Principle #10Preliminary action

2Quantity of substance

If memory cells are programmed to higher threshold voltage states, then the storage density is improved, but charge loss and over-programming errors increase

Engineering Contradiction:

Improvestorage densityVSAvoidprogram error rate

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent implements verify read operations after programming each page to detect charge loss and over-programming errors. The verify voltage is dynamically adjusted based on the threshold voltage distribution established by previously programmed pages, allowing the system to detect and correct errors before they propagate to subsequent programming operations

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent changes the verify voltage parameter dynamically during the programming process. The verify voltage is set relative to the threshold voltage distribution of previously programmed pages, allowing the verification process to adapt to the current state of memory cells and detect errors caused by charge loss or over-programming

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS7903467B2Programming method of multi-bit flash memory device for reducing programming error

Publication Date: 2011.03.08 SAMSUNG ELECTRONICS CO LTD

AI summary

A method of programming a plurality of memory cells of a flash memory device by selectively changing a threshold voltage distribution thereof from a first distribution to a second distribution, the method includes selecting at least one of the memory cells to be programmed, and programming the at least one selected memory cell to a voltage higher than a verify voltage, wherein the verify voltage is one of threshold voltages included in the first distribution or is higher than the threshold voltages included in the first distribution.