Nonvolatile Memory Leakage Compensation via Dummy Cell Biasing

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Solution Overview

Problem

Nonvolatile memory devices face reliability issues due to uneven leakage current in memory cells, which can cause operational errors, particularly in PRAM, MRAM, and RRAM, where structural characteristics lead to inadvertent current leakage.

Innovation Solution

The introduction of dummy cells and a bias circuit system that adjusts the leakage current by applying specific voltages to dummy word lines and bit lines, using a leakage detector to maintain a uniform leakage current level across memory cells, thereby stabilizing the bias voltage and reducing operational errors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If dummy cells and bias circuits are added to control leakage current, then reliability is improved, but device complexity increases

Engineering Contradiction:

ImprovereliabilityVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The memory array is segmented into functional memory cells and dummy cells. The dummy cells are specifically designed to mirror the structure of functional cells but are dedicated solely to leakage detection and compensation purposes, allowing independent control and measurement without affecting normal memory operations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Dummy cells act as intermediary elements between the memory array and the leakage detection system. They provide a controlled interface for measuring leakage current characteristics without directly interfering with the functional memory cells, enabling indirect monitoring and compensation of leakage effects.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If leakage current is controlled through dummy cells and bias adjustment, then operational error is reduced, but manufacturing complexity increases

Engineering Contradiction:

Improveoperational errorVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The system dynamically adjusts bias voltages applied to dummy cells based on detected leakage current levels. By changing voltage parameters in real-time, the system compensates for leakage variations without requiring physical modifications to the memory cell structure or additional manufacturing steps.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The memory system performs self-diagnosis and self-correction by using dummy cells to detect leakage current and automatically adjusting bias conditions to compensate for detected issues, eliminating the need for external calibration or manual intervention during operation.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS10431300B2Nonvolatile memory device and operating method of nonvolatile memory device

Publication Date: 2019.10.01 SAMSUNG ELECTRONICS CO LTD

AI summary

A memory device includes a delay locked loop that generates a first code for delaying a reference clock in a first operation mode that is a normal operation mode, generates a second code for delaying the reference clock in a second operation mode that is a refresh mode, and delays the reference clock in response to one of the first and second codes depending on one of the first and second operation modes, and a data output circuit that outputs a data strobe signal (DQS) using the delayed reference clock.