Oxide Thin-Film Transistor Buffer Layer for Hydrogen Blocking

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Solution Overview

Problem

Transistors fabricated in the back end of line (BEOL) portion of the semiconductor fabrication process are sensitive to hydrogen gas and free hydrogen atoms, which can diffuse and react with the channel layer, leading to doping and adverse effects on the electrical properties, such as a strong negative threshold voltage shift.

Innovation Solution

Incorporating a buffer layer between the source/drain contacts and the channel layer, formed from different materials or with different structural properties, to absorb hydrogen gas and free hydrogen atoms, thereby reducing hydrogen diffusion and its impact on the channel layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If transistors are fabricated in the back end of line (BEOL) portion of the semiconductor fabrication process, then manufacturing flexibility and integration are improved, but the transistors become sensitive to hydrogen gas and free hydrogen atoms that can diffuse and react with the channel layer, causing doping and adverse electrical effects

Engineering Contradiction:

Improvemanufacturing flexibilityVSAvoidhydrogen diffusion

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

A buffer layer is introduced as an intermediary component between the source/drain contacts and the channel layer. This buffer layer acts as a mediator that captures and holds hydrogen atoms, preventing them from diffusing into the channel layer and causing harmful doping effects, while allowing the transistor to function normally in the BEOL fabrication process

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a buffer layer is incorporated between the source/drain contacts and the channel layer, then hydrogen diffusion is reduced and electrical properties are improved, but device structure becomes more complex

Engineering Contradiction:

Improveelectrical propertiesVSAvoidstructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The transistor structure is segmented into distinct functional layers, with the buffer layer forming a separate segment between the source/drain contacts and the channel layer. This segmentation allows the buffer layer to perform its hydrogen-capturing function independently while maintaining the overall integrity and simplicity of the device structure

Inventive Principle:

Principle #1Segmentation

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 buffer layer effectively reduces hydrogen diffusion, minimizing the adverse effects on the channel layer's electrical properties and improving the robustness of the transistors by preventing hydrogen-induced doping and threshold voltage shifts.

Implementation Method 1

Methodology Applied

Scientific EffectAbsorption: Absorption (physical)

Implementation Method 2

hydrogen gas and free hydrogen atoms, which can diffuse and react with the channel layer

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS11869975B2Thin-film transistors and method for manufacturing the same

Publication Date: 2024.01.09 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A transistor includes a gate electrode, a gate dielectric located over the gate electrode, a channel layer that includes an oxide semiconductor material and that is located over the gate dielectric, a buffer located to cover at least a portion of the channel layer, and source/drain contacts disposed on the buffer. The buffer includes a material that receives hydrogen. A method for manufacturing the transistor is also provided.