Double-Gate FeFET Structure for Stable Ferroelectric Integration

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Solution Overview

Problem

It is challenging to integrate ferroelectric materials with semiconductor device materials and structures while maintaining suitable ferroelectric properties and device performance, particularly in forming ferroelectric field effect transistors (FeFETs) with oxide semiconductors.

Innovation Solution

The development of FeFET devices with a double gate structure, where a first ferroelectric material layer is disposed between a gate electrode and one side of a channel layer, and a second ferroelectric material layer is disposed between a second gate electrode and the opposite side of the channel layer, allowing for improved polarization, memory window, and on-current through common or separated gate control modes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If ferroelectric materials are integrated with semiconductor device materials and structures, then device performance and ferroelectric properties can be maintained, but integration difficulty increases

Engineering Contradiction:

Improveferroelectric propertiesVSAvoidintegration difficulty

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The device is divided into two separate gates (top gate and bottom gate) with ferroelectric layers positioned between each gate and the channel layer. This segmentation allows independent optimization of each gate-ferroelectric interface, simplifying the integration process while maintaining ferroelectric properties in each layer

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The channel layer acts as an intermediary between the two ferroelectric layers, enabling the integration of multiple ferroelectric materials with different semiconductor materials. The channel layer mediates the interface between ferroelectric and semiconductor materials, facilitating integration while preserving ferroelectric properties

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a double gate structure with ferroelectric layers is used, then polarization and memory window increase, but device complexity increases

Engineering Contradiction:

ImprovepolarizationVSAvoidstructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The single gate structure is segmented into two separate gates (top and bottom), each with its own ferroelectric layer. This segmentation enables independent control of polarization in each layer, increasing total polarization and memory window while managing complexity through modular design

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The double gate structure provides multi-functionality by enabling both independent gate control modes and combined gate control modes. The device can operate in different modes (independent control for fine-tuning, combined control for maximum performance), making the increased structural complexity worthwhile through enhanced functional capabilities

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If a double gate structure with ferroelectric layers is used, then memory window and on-current increase, but device complexity increases

Engineering Contradiction:

Improvememory windowVSAvoidstructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The memory window enhancement is achieved through segmentation into two ferroelectric layers that can contribute additively to the total memory window. Each layer can be optimized independently to maximize its contribution, increasing overall memory window while managing complexity through modular optimization

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The device transitions from a single-gate two-dimensional control to a double-gate three-dimensional control structure. This dimensional change enables enhanced memory window and on-current by utilizing the vertical stacking of ferroelectric layers, achieving performance improvement through spatial expansion

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 configuration enhances the reliability and performance of FeFET-based memory devices by increasing polarization, memory window, and on-current, while maintaining stable ferroelectric properties, enabling effective encoding and reading of logic states.

Implementation Method 1

a first ferroelectric material layer is disposed between a gate electrode and one side of a channel layer, and a second ferroelectric material layer is disposed between a second gate electrode and the other side of the channel layer

Methodology Applied

Scientific EffectFerroelectricity:

Data Source

PatentUS11908936B2Double gate ferroelectric field effect transistor devices and methods for forming the same

Publication Date: 2024.02.20 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A ferroelectric field effect transistor (FeFET) having a double-gate structure includes a first gate electrode, a first ferroelectric material layer over the first gate electrode, a semiconductor channel layer over the first ferroelectric material layer, source and drain electrodes contacting the semiconductor channel layer, a second ferroelectric material layer over the semiconductor channel layer, and a second gate electrode over the second ferroelectric material layer.