Thin-Film Transistor Passivation Stack for Leakage and Stability

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Solution Overview

Problem

Thin film transistors face challenges with increased leakage current and reduced drive current due to material degradation during fabrication processes, particularly in back-gated devices, which affect stability and performance.

Innovation Solution

Implementing a multi-layer passivation structure comprising a barrier layer, etch stop layer, and sealant layer to protect the channel layer from oxygen vacancy migration and hydrogen exposure, along with an electrical barrier layer to repel charge accumulation, thereby enhancing device stability and reducing leakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a thin film transistor uses non-silicon channel materials, then device performance and stability are improved, but resistance between drain and gate increases during operation

Engineering Contradiction:

Improvedevice stabilityVSAvoidresistance between drain and gate

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a passivation layer as an intermediary between the channel layer and the environment. This passivation layer prevents harmful interactions (oxygen exposure, hydrogen ingress) that cause material degradation and increased resistance, thereby resolving the contradiction between using non-silicon channel materials and maintaining low resistance during operation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent creates an inert environment by sealing the channel layer with a passivation layer that prevents oxygen and moisture exposure. This inert environment protects the non-silicon channel material from degradation, maintaining device stability and preventing resistance increase during operation.

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

2Ease of manufacture

If fabrication processes are performed without passivation, then manufacturing simplicity is maintained, but channel layer material degradation occurs due to oxygen vacancy migration and hydrogen exposure

Engineering Contradiction:

Improvefabrication simplicityVSAvoidchannel layer material stability

Core Design Contradiction:

Ease of manufactureVSStability of the object's composition

Solution Approach 1:

The patent applies preliminary protection by forming a passivation layer during the fabrication process that prevents oxygen vacancy migration and hydrogen exposure before they can degrade the channel layer. This preliminary action maintains material stability without significantly complicating the fabrication process.

Inventive Principle:

Principle #10Preliminary action

3Device complexity

If no passivation structure is implemented, then device complexity is reduced, but leakage current increases and drive current decreases

Engineering Contradiction:

Improvepassivation structure complexityVSAvoidtransistor performance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent employs a composite passivation structure consisting of multiple layers (e.g., aluminum oxide, silicon nitride) that work together to provide comprehensive protection. This composite approach effectively reduces leakage current and maintains drive current while keeping the added complexity manageable through the use of standard semiconductor materials and processes.

Inventive Principle:

Principle #40Composite materials

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 multi-layer passivation structure improves on-current by over two decades and significantly reduces off-state leakage, stabilizing the thin film transistor performance.

Implementation Method 1

protect the channel layer from oxygen vacancy migration

Methodology Applied

Scientific EffectOxygen vacancy migration: Diffusion

Implementation Method 2

protect the channel layer from oxygen vacancy migration and hydrogen exposure

Methodology Applied

Scientific EffectHydrogen exposure: Absorption (physical)

Implementation Method 3

an electrical barrier layer to repel charge accumulation

Methodology Applied

Scientific EffectElectrostatic repulsion: Electrostatics

Data Source

PatentUS12376342B2Passivation layers for thin film transistors

Publication Date: 2025.07.29 INTEL CORP

AI summary

A thin film transistor (TFT) structure includes a gate electrode, a gate dielectric layer on the gate electrode, a channel layer including a semiconductor material with a first polarity on the gate dielectric layer. The TFT structure also includes a multi-layer material stack on the channel layer, opposite the gate dielectric layer, an interlayer dielectric (ILD) material over the multi-layer material stack and beyond a sidewall of the channel layer. The TFT structure further includes source and drain contacts through the interlayer dielectric material, and in contact with the channel layer, where the multi-layer material stack includes a barrier layer including oxygen and a metal in contact with the channel layer, where the barrier layer has a second polarity. A sealant layer is in contact with the barrier layer, where the sealant layer and the ILD have a different composition.