Oxide Semiconductor Transistor Structure for Moisture-Stable Display Switching

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Transistors used in display devices face challenges in achieving high on-off ratios and operation speed, particularly in pixel and driver circuits, due to issues like moisture-induced degradation and parasitic channel generation in oxide semiconductor layers.

Innovation Solution

A transistor design featuring an oxide semiconductor layer with a microcrystal c-axis-oriented superficial region and an amorphous or mixed amorphous-microcrystal rest region, formed through dehydration or dehydrogenation using an RTA method, which reduces contact resistance and suppresses parasitic channel formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If an oxide semiconductor layer is used to form a channel region, then high field effect mobility is achieved, but moisture-induced degradation and parasitic channel generation occur

Engineering Contradiction:

Improvefield effect mobilityVSAvoidresistance to moisture-induced degradation

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The oxide semiconductor layer is structured with a first region (superficial portion) having microcrystals with c-axis orientation and a second region (rest portion) being amorphous or having mixed amorphous-microcrystal structure. This local differentiation allows the superficial region to provide high mobility while the amorphous region resists moisture-induced degradation and parasitic channel generation.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The oxide semiconductor layer combines crystalline and amorphous phases within a single layer structure. The microcrystalline region provides high field effect mobility while the amorphous region provides resistance to moisture-induced degradation, creating a composite material with both properties simultaneously.

Inventive Principle:

Principle #40Composite materials

2Speed

If the oxide semiconductor layer is made highly crystalline to improve mobility, then operation speed increases, but parasitic channel generation increases

Engineering Contradiction:

Improveoperation speedVSAvoidparasitic channel generation

Core Design Contradiction:

SpeedVSObject-generated harmful factors

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention changes the structural parameters of the oxide semiconductor layer by creating regions with different crystallinity levels. The superficial region has high crystallinity for mobility, while the rest portion has low crystallinity (amorphous or mixed) to suppress parasitic channels, optimizing both performance and reliability.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If dehydration or dehydrogenation is performed at high temperature for a short time, then the superficial portion becomes microcrystalline improving contact resistance, but the rest portion remains amorphous maintaining low parasitic channel

Engineering Contradiction:

Improvecontact resistanceVSAvoidlayer structure complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The invention uses rapid thermal annealing (RTA) to perform dehydration or dehydrogenation at high temperature for a short time. This periodic thermal action selectively crystallizes the superficial portion while maintaining the amorphous nature of the rest portion, achieving the desired dual-structure without excessive complexity.

Inventive Principle:

Principle #19Periodic action

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 solution provides transistors with improved electric characteristics and reliability, enabling high-speed operation and stable performance in display devices by preventing degradation and enhancing contact resistance between electrodes.

Implementation Method 1

As the oxide semiconductor layer, the one on which dehydration or dehydrogenation is performed with an RTA method or the like at high temperature for a short time is used.

Methodology Applied

Scientific EffectRapid Thermal Annealing (RTA): Heat Treatment

Implementation Method 2

Through this heating step, the superficial portion of the oxide semiconductor layer comes to include a crystal region formed of microcrystals

Methodology Applied

Scientific EffectCrystallization: Crystallisation

Data Source

PatentUS20240055533A1Transistor and display device

Publication Date: 2024.02.15 SEMICON ENERGY LAB CO LTD

AI summary

To provide a transistor having a favorable electric characteristics and high reliability and a display device including the transistor. The transistor is a bottom-gate transistor formed using an oxide semiconductor for a channel region. An oxide semiconductor layer subjected to dehydration or dehydrogenation through heat treatment is used as an active layer. The active layer includes a first region of a superficial portion microcrystallized and a second region of the rest portion. By using the oxide semiconductor layer having such a structure, a change to an n-type, which is attributed to entry of moisture to the superficial portion or elimination of oxygen from the superficial portion, and generation of a parasitic channel can be suppressed. In addition, contact resistance between the oxide semiconductor layer and source and drain electrodes can be reduced.