Transfer Transistor Voltage Transfer Reliability

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Solution Overview

Problem

Conventional NAND cell type flash memories face challenges in efficiently transferring high voltages required for data writing, particularly in preventing the formation of depletion regions that can impede the transfer of high voltage to memory cells, especially when dealing with multivalue data storage.

Innovation Solution

The design incorporates transfer transistors with a specific diffused region structure and M0 wires that are supplied with a predetermined voltage to prevent depletion region formation, ensuring effective high-voltage transfer by applying the same voltage to the gate electrode and M0 wires, thereby maintaining efficient operation and layout flexibility.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If transfer transistors are used to transfer high voltage for data writing, then data writing capability is improved, but depletion regions form in the diffused regions which impede voltage transfer

Engineering Contradiction:

Improvehigh voltage transfer reliabilityVSAvoiddepletion region formation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies equipotentiality by supplying the same predetermined voltage to both the gate electrode and the M0 wire. This creates equipotential regions that prevent potential differences from causing depletion region formation in the third diffused region, thereby ensuring reliable high voltage transfer without the harmful depletion effect

Inventive Principle:

Principle #12Equipotentiality

Solution Approach 2:

The M0 wire acts as an intermediary element between the control gate line and the third diffused region. By introducing this intermediate conductive structure and supplying it with an appropriate predetermined voltage, the patent mediates the voltage transfer process to prevent depletion region formation while maintaining effective control over the transfer transistor

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the same voltage is applied to gate electrode and M0 wire, then depletion region formation is prevented, but device complexity increases

Engineering Contradiction:

Improvevoltage transfer efficiencyVSAvoidvoltage supply structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The M0 wire serves multiple functions: it acts as a voltage supply line for the third diffused region, functions as a control electrode to prevent depletion region formation, and can be integrated with existing control gate line structures. This multi-functionality reduces the need for separate dedicated structures, thereby limiting the increase in device complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Quantity of substance

If transfer transistors transfer high voltage for multivalue data storage, then storage capacity is improved, but voltage margin becomes insufficient due to depletion regions

Engineering Contradiction:

Improvedata storage capacityVSAvoidvoltage margin

Core Design Contradiction:

Quantity of substanceVSUse of energy by moving object

Solution Approach 1:

By creating equipotential conditions through supplying the same predetermined voltage to the gate electrode and M0 wire, the patent eliminates potential differences that would otherwise cause depletion regions. This ensures sufficient voltage margin is maintained across the transfer transistor, enabling reliable multivalue data storage operations with adequate voltage headroom

Inventive Principle:

Principle #12Equipotentiality

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 solution enables reliable and efficient transfer of high voltages to memory cells, preventing depletion region formation and ensuring sufficient voltage margin for multivalue data storage, while also providing design arbitrariness in the layout of upper layer wires.

Implementation Method 1

a first wire supplied with at least a predetermined voltage for preventing formation of a depletion region in the third diffused region when the transfer transistor transfers the voltage used for writing

Methodology Applied

Scientific EffectDepletion region formation: Electric Field

Data Source

PatentUS8334557B2Nonvolatile semiconductor storage device including a transfer transistor

Publication Date: 2012.12.18 KIOXIA CORP

AI summary

A first diffused region is formed in a surface of a semiconductor substrate located under a gate electrode. A second diffused region is formed in a surface of the semiconductor substrate adjoining the first diffused region on a first side thereof. A third diffused region is formed in a surface of the semiconductor substrate adjoining the first diffused region on a second side thereof. The first side and the second side are opposite to one another. A first wire is disposed above an overlapping region where the first and third diffused regions overlap. The first wire is supplied with at least a certain voltage for preventing formation of a depletion region in the third diffused region when transfer transistor transfers the voltage used for writing.