Flash Memory Programming via Proximate Cell Voltage Adjustment

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Solution Overview

Problem

The existing flash memory devices face challenges in accurately programming flash memory cells due to coupling effects between adjacent cells, leading to inefficiencies and potential read data errors as the spacing between cells decreases, necessitating a method to compensate for these intercellular coupling effects.

Innovation Solution

The proposed solution involves a flash memory device with a control logic unit that reads and temporarily stores data from adjacent rows, adjusts the read threshold voltage levels, and applies a program/verify loop to program cells to slightly lower target threshold voltages, then updates the threshold voltage sets to maintain accurate bit state assignments and prevent data errors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If flash memory cells are programmed using conventional methods, then programming can be completed, but coupling effects between adjacent cells cause threshold voltage shifts leading to read data errors

Engineering Contradiction:

Improvedata accuracyVSAvoidcoupling effects

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by adjusting the threshold voltage of proximate memory cells before programming the target cell. The control logic determines the initial threshold voltage of proximate cells, calculates adjusted threshold voltages that compensate for expected coupling effects, and programs the proximate cells to these adjusted voltages beforehand. This preliminary adjustment prevents the coupling effects from causing read data errors when the target cell is subsequently programmed and read.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If iterative programming loops are used to achieve accurate threshold voltages, then programming precision is improved, but programming time and complexity increase

Engineering Contradiction:

Improvethreshold voltage precisionVSAvoidprogramming time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The patent eliminates iterative programming loops by performing preliminary calculations of adjusted threshold voltages before programming begins. The control logic calculates the exact threshold voltage adjustments needed for proximate cells based on their initial voltages and the target cell's programming parameters. This preliminary calculation allows all cells to be programmed in a single pass with the correct final voltages, avoiding the time-consuming iterative verify-and-adjust cycles of conventional methods.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback by having the control logic continuously monitor the threshold voltages of proximate memory cells during programming operations. Based on this feedback information about the actual voltage states, the control logic dynamically adjusts the programming parameters for both proximate and target cells to compensate for coupling effects. This feedback mechanism ensures precise final threshold voltages without requiring multiple iterative loops.

Inventive Principle:

Principle #23Feedback

3Quantity of substance

If spacing between memory cells is reduced to increase density, then storage capacity is improved, but coupling effects between cells intensify causing more read errors

Engineering Contradiction:

Improvestorage densityVSAvoidintercellular coupling

Core Design Contradiction:

Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

The patent applies parameter changes by dynamically adjusting the threshold voltage parameters of proximate memory cells based on their initial states and the programming requirements of target cells. The control logic calculates adjusted threshold voltages that account for the intensified coupling effects caused by reduced cell spacing. By changing the voltage parameters of proximate cells to these adjusted values before programming, the patent compensates for the stronger coupling effects and prevents read data errors even at high storage densities.

Inventive Principle:

Principle #35Parameter changes

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 allows for more precise programming of flash memory cells by compensating for coupling effects, reducing the need for iterative programming and minimizing data errors, thereby improving the efficiency and accuracy of programming and reading operations.

Implementation Method 1

coupling effects between adjacent cells

Methodology Applied

Scientific EffectCoupling effects:

Implementation Method 2

programmed by storing charge on the floating gate

Methodology Applied

Scientific EffectCharge transfer:

Data Source

PatentUS9177653B2Method and system for programming non-volatile memory cells based on programming of proximate memory cells

Publication Date: 2015.11.03 MICRON TECHNOLOGY INC

AI summary

A multi-level non-volatile memory device programs cells in each row in a manner that takes into account the coupling from the programming of cells that are proximate the row to be programmed. In one example of the invention, after the row has been programmed, the proximate cells are verified by read, comparison, and, if necessary, reprogramming operations to compensate for charge added to proximate memory cells resulting from programming the row. In another example of the invention, a row of memory cells is programmed with charge levels that take into account the charge that will be added to the memory cells when proximate memory cells are subsequently programmed.