Flash Memory CSL Feedback Circuit for Noise Reduction

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Solution Overview

Problem

Flash memory devices face challenges in maintaining narrow threshold voltage distributions due to common source line (CSL) noise, which affects data retention and programming accuracy in multi-level cell (MLC) devices.

Innovation Solution

The implementation of a CSL feedback circuit and CSL feedback control logic that detects voltage changes in the common source line and compensates the selected word or bit line to maintain a constant voltage level during sensing operations, independent of CSL voltage changes, thereby preventing the spreading of threshold voltage distributions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If flash memory devices use multi-level cells (MLC) to increase storage capacity, then data storage capacity is improved, but threshold voltage distributions spread out due to CSL noise causing programming accuracy to deteriorate

Engineering Contradiction:

Improvedata storage capacityVSAvoidprogramming accuracy

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

The patent implements a common source line (CSL) feedback circuit that detects voltage changes on the CSL and applies compensating voltages to word lines or bit lines. This feedback mechanism counteracts CSL noise effects, maintaining narrow threshold voltage distributions and improving programming accuracy while preserving the high storage capacity of MLC devices

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent dynamically adjusts voltage parameters (word line voltages or bit line voltages) based on detected CSL voltage changes. By changing these voltage parameters in real-time compensation, the system maintains adequate margins between threshold voltage distributions despite the presence of CSL noise, thereby improving programming accuracy

Inventive Principle:

Principle #35Parameter changes

2Productivity

If flash memory devices perform read operations on MLCs, then data retrieval is enabled, but CSL noise causes threshold voltage distributions to spread reducing data retention reliability

Engineering Contradiction:

Improvedata retrieval speedVSAvoiddata retention reliability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The CSL feedback circuit operates during read operations to detect and compensate for voltage changes on the common source line. This real-time feedback compensation prevents threshold voltage distribution spreading, maintaining reliable data retention while enabling fast data retrieval from MLC devices

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The feedback circuit applies compensating voltages before CSL noise can significantly affect the read operation. By counteracting the noise effects in advance, the system prevents threshold voltage spreading and maintains data retention reliability throughout the read operation

Inventive Principle:

Principle #9Preliminary anti-action

3Productivity

If flash memory devices increase programming speed, then productivity is improved, but CSL noise effects become more significant causing threshold voltage distributions to spread

Engineering Contradiction:

Improveprogramming speedVSAvoidthreshold voltage distribution narrowness

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The feedback circuit provides real-time compensation during high-speed programming operations, detecting CSL voltage changes and applying corrective voltages to maintain narrow threshold voltage distributions. This enables fast programming while preserving programming precision

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The feedback compensation operates continuously throughout the programming process, ensuring that threshold voltage distributions remain narrow even during high-speed operations. This continuous compensation maintains manufacturing precision without sacrificing programming speed

Inventive Principle:

Principle #20Continuity of useful action

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 noise-induced errors, maintaining accurate data storage and programming by keeping the threshold voltage distributions narrow, enhancing the reliability of flash memory devices.

Implementation Method 1

a CSL feedback circuit connected to the common source line to detect a voltage level of the common source line

Methodology Applied

Scientific EffectVoltage detection: Electric Field

Implementation Method 2

CSL feedback control logic configured to control a voltage level of a selected word line or a selected bit line to be compensated to a constant level based on the voltage level detected by the CSL feedback circuit

Methodology Applied

Scientific EffectVoltage compensation: Feedback

Data Source

PatentUS8264888B2Flash memory device configured to reduce common source line noise, methods of operating same, and memory system incorporating same

Publication Date: 2012.09.11 SAMSUNG ELECTRONICS CO LTD

AI summary

A flash memory device comprises memory cells connected between a bit line and a common source line, word lines connected to the memory cells, a common source line feedback circuit connected to a common source line (CSL) to detect the voltage level of the common source line, and a CSL feedback control logic configured to control a voltage level of a selected word line or a selected bit line to be compensated to a substantially constant value during a sensing operation of the memory cells based on the detected voltage level of the CSL.