Memory Device Dummy Cell Programming for Leakage Suppression

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Leakage currents in vertically stacked normal cells of memory devices increase integration density but pose operational challenges, such as error rates and charge leakage, due to voltage differences and transistor characteristics.

Innovation Solution

Incorporating a dummy program controller to generate control signals for programming dummy cells using mechanisms like hot carrier injection (HCI) or Fowler-Nordheim tunneling, which increases threshold voltages, thereby optimizing dummy cell programming to reduce leakage and enhance operational reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If normal cells are vertically stacked to increase integration density, then integration density is improved, but leakage currents increase

Engineering Contradiction:

Improveintegration densityVSAvoidleakage currents

Core Design Contradiction:

Quantity of substanceVSObject-generated harmful factors

Solution Approach 1:

The patent applies preliminary action by programming dummy cells before normal cells during the programming process. The dummy program controller generates control signals to program dummy cells in advance, establishing a reference threshold voltage that compensates for leakage effects before the actual data programming occurs. This preliminary programming action prevents leakage-induced errors during normal cell operation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces dummy cells as intermediary elements between the control circuitry and normal cells. These dummy cells serve as a buffer or mediator that absorbs leakage effects and provides a reference for threshold voltage compensation. The dummy program controller and associated circuitry act as intermediary components that manage the programming process to mitigate leakage impacts on normal cells.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-generated harmful factors

If dummy cells are programmed before normal cells, then leakage suppression is improved, but device complexity increases

Engineering Contradiction:

Improveleakage suppressionVSAvoiddevice complexity

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The patent merges the dummy cell programming function with the existing memory cell array structure. The dummy cells are integrated into the same physical array as normal cells, sharing common bit lines, word lines, and select transistors. The controller combines dummy cell programming with normal cell programming operations, using unified control signal generation and voltage application mechanisms, thereby reducing the complexity overhead of adding dummy cells.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The dummy cells and their programming circuitry serve multiple functions: they provide leakage compensation, establish threshold voltage references, and can be programmed using the same mechanisms as normal cells. The dummy program controller can operate in conjunction with the normal program controller, and the same voltage generation and signal routing infrastructure serves both dummy and normal cell programming, reducing overall system complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

The proposed solution effectively suppresses leakage phenomena by optimizing dummy cell threshold voltages, improving the reliability and uniformity of programming across non-uniform cell strings, thus enhancing the overall performance and control of memory devices.

Implementation Method 1

The dummy program controller may generate the second control signal such that the second control signal may correspond to programming the at least one dummy cell by a hot carrier injection (HCI) mechanism to increase a threshold voltage of the at least one dummy cell.

Methodology Applied

Scientific EffectHot carrier injection (HCI):

Implementation Method 2

The dummy program controller may generate the second control signal such that second control signal may correspond to programming the at least one dummy cell by a Fowler-Nordheim (F-N) tunneling mechanism to increase a threshold voltage of the at least one dummy cell.

Methodology Applied

Scientific EffectFowler-Nordheim tunneling:

Data Source

PatentUS9721664B2Memory devices and methods of operating the memory devices by programming normal cells after programming a first dummy cell

Publication Date: 2017.08.01 SAMSUNG ELECTRONICS CO LTD

AI summary

A method of operating a memory device including a first memory block having a plurality cell strings is provided. Each of the plurality of cell strings includes a string selection transistor connected in series to a first dummy cell, a plurality of normal cells, a second dummy cell and a ground selection transistor. The method includes programming the first dummy cell, and programming the normal cells in at least one of the cell strings after the programming the first dummy cell. The normal cells are selected based on a first program command inputted to the memory device. The programming the first dummy cell is performed at least twice before the normal cells are programmed. A number of times of programming the first dummy cell is different according to a level of a voltage applied to the first dummy cell and a level of a voltage applied to the normal cells.