Partial Refresh During Flash Memory Erase

Solution Overview

Problem

Flash memory devices face limited lifespan due to program/erase cycle wear, requiring higher voltages for programming and erasing, leading to data retention issues, especially as block sizes increase while data file sizes remain static, necessitating an effective method to reduce unnecessary erase time and extend device life.

Innovation Solution

A method for partial refresh of non-volatile memory devices, dividing the memory into a target erase area and an unselected area, where the unselected area is conditioned and partially refreshed, reducing the total erase time by focusing on specific portions rather than the entire block.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the entire block is erased before programming, then data integrity is maintained, but erase time increases and device lifespan decreases

Engineering Contradiction:

Improvedata integrityVSAvoiderase time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The memory block is divided into a target erase area (where data needs to be updated) and an unselected area. Only the target erase area is fully erased, while the unselected area undergoes partial refresh. This segmentation allows selective erasing based on data validity, reducing unnecessary erase operations and time.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of erasing the entire block, the patent applies partial erase to only the necessary target area. The unselected area receives a partial refresh operation rather than a full erase, which is sufficient to maintain data integrity without the time cost of a complete erase operation.

Inventive Principle:

Principle #16Partial or excessive action

2Reliability

If the entire block is erased before programming, then data integrity is maintained, but device lifespan decreases

Engineering Contradiction:

Improvedata integrityVSAvoiddevice lifespan

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The memory block is divided into a target erase area (where data needs to be updated) and an unselected area. Only the target erase area is fully erased, while the unselected area undergoes partial refresh. This segmentation allows selective erasing based on data validity, reducing unnecessary erase operations and time.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of erasing the entire block, the patent applies partial erase to only the necessary target area. The unselected area receives a partial refresh operation rather than a full erase, which is sufficient to maintain data integrity without the time cost of a complete erase operation.

Inventive Principle:

Principle #16Partial or excessive action

3Quantity of substance

If block size increases while data file size remains static, then storage capacity improves, but unnecessary erase operations increase

Engineering Contradiction:

Improvestorage capacityVSAvoiderase time

Core Design Contradiction:

Quantity of substanceVSLoss of time

Solution Approach 1:

The memory block is divided into a target erase area (where data needs to be updated) and an unselected area. Only the target erase area is fully erased, while the unselected area undergoes partial refresh. This segmentation allows selective erasing based on data validity, reducing unnecessary erase operations and time.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different operations are applied to different areas of the memory block based on their specific needs. The target erase area receives a full erase operation to ensure data integrity, while the unselected area receives a partial refresh operation. This local differentiation optimizes erase time while maintaining storage capacity.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS8804436B1Method of partial refresh during erase operation

Publication Date: 2014.08.12 WINBOND ELECTRONICS CORP

AI summary

A method of erasing a target erase area of a non-volatile memory is provided, wherein the non-volatile memory is divided into an target erase area and an unselected area, and the method includes the steps in an erase cycle of: conditioning the target erase area of the non-volatile memory, wherein the unselected area is an area, excluding the target erase area, in the non-volatile memory; erasing target cells of the target erase area, wherein the threshold of the target cells is not greater than an erase verify voltage; soft-programming the target cells, wherein the threshold of the target cells is not less than a soft program verify voltage, wherein the soft program verify voltage is less than the erase verify voltage; and refreshing a predefined portion of the unselected area, wherein the predefined portion in the erase cycle is less than the unselected area.