Non-Volatile Memory Pre-Charge Boosting to Eliminate Program Disturb

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Solution Overview

Problem

Existing flash memory systems face challenges in preventing program disturb, where unselected cells connected to the same word line as the selected cell for programming are inadvertently programmed, due to the application of program voltage to all cells on a word line, leading to errors and data integrity issues.

Innovation Solution

The solution involves pre-charging unselected groups of non-volatile storage elements to a higher boosted potential before applying the program voltage to the selected word line, using different pre-charge enable voltages for cells that have undergone partial programming to ensure proper pre-charging and boosting, thereby reducing or eliminating program disturb.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If program voltage is applied to all cells on a word line, then programming of selected cells is achieved, but unselected cells are inadvertently programmed causing program disturb

Engineering Contradiction:

Improveprogramming speedVSAvoiddata integrity

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent divides the word line into selected and unselected cell groups, applying different voltage treatments. Selected cells receive program voltage while unselected cells receive boosting voltage to prevent inadvertent programming, thus segmenting the treatment based on selection status.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies pre-charge and boosting voltages to unselected cells before applying program voltage to selected cells. This preliminary action ensures unselected cells are in a state resistant to program disturb before the programming operation begins.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If pre-charge is applied to unselected cells, then program disturb is reduced, but dependency on word line data creates complexity

Engineering Contradiction:

Improveprogram disturb reductionVSAvoidpre-charge control complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies different pre-charge enable voltages to different sets of unselected cells based on their specific conditions. First set cells receive first pre-charge enable voltages while second set cells receive second pre-charge enable voltages, tailoring the pre-charge treatment to local cell conditions.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the voltage parameters applied to unselected cells based on their programming state. By detecting whether cells have undergone partial programming and adjusting pre-charge enable voltages accordingly, the system optimizes program disturb reduction while managing complexity through conditional parameter adjustment.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If different pre-charge enable voltages are used for partially programmed cells, then pre-charging accuracy is improved, but control complexity increases

Engineering Contradiction:

Improvepre-charge voltage accuracyVSAvoidvoltage control complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent implements dynamic voltage selection where pre-charge enable voltages are adjusted based on the programming state of cells. The system dynamically determines which voltage level to apply to each cell set, optimizing pre-charge accuracy while adapting to changing cell states during the programming process.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent uses feedback from cell programming status to determine appropriate pre-charge enable voltages. By monitoring whether cells have undergone partial programming and using this information to select appropriate voltage levels, the system achieves precise voltage control while managing complexity through feedback-driven decision making.

Inventive Principle:

Principle #23Feedback

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach effectively reduces or eliminates program disturb by ensuring that unselected cells are not inadvertently programmed, improving data integrity and accuracy during the programming process.

Implementation Method 1

pre-charging unselected groups of non-volatile storage elements to a higher boosted potential before applying the program voltage

Methodology Applied

Scientific EffectElectrical potential boosting: Capacitance

Data Source

PatentUS7433241B2Programming non-volatile memory with reduced program disturb by removing pre-charge dependency on word line data

Publication Date: 2008.10.07 SANDISK TECHNOLOGIES LLC

AI summary

Unselected groups of non-volatile storage elements are boosted during programming to reduce or eliminate program disturb for targeted, but unselected memory cells connected to a selected word line. Prior to applying a program voltage to the selected word line and boosting the unselected groups, the unselected groups are pre-charged to further reduce or eliminate program disturb by providing a larger boosted potential for the unselected groups. During pre-charging, one or more pre-charge enable signals are provided at higher voltages for certain memory cells that may have undergone partial programming.