Oxynitride Gate Insulator for High Mobility TFT Uniformity

Solution Overview

Problem

Conventional liquid crystal display (LCD) thin film transistors (TFTs) face challenges in achieving high charge mobility and uniform electrical characteristics over large-sized display devices, with amorphous silicon TFTs having low mobility and polysilicon TFTs requiring high uniformity.

Innovation Solution

A TFT array substrate is designed with a semiconductive oxide layer on an insulating substrate, featuring a gate electrode overlapping the oxide layer, a gate insulating layer with a higher oxygen concentration than nitrogen, and a passivation layer with an oxynitride structure, ensuring high charge mobility and uniformity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If amorphous silicon TFT is used, then uniformity in electrical characteristics is achieved, but charge mobility remains low

Engineering Contradiction:

Improveuniformity in electrical characteristicsVSAvoidcharge mobility

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The patent employs a composite gate insulating layer structure combining silicon oxide and silicon nitride layers. The silicon oxide layer provides good interface characteristics with the semiconductor layer, while the silicon nitride layer contributes to stable electrical properties and reduced defect density. This composite structure enables both high charge mobility and uniform electrical characteristics across large display areas.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent optimizes the thickness parameters of the gate insulating layer components, with the silicon oxide layer being 50-150 nm thick and the silicon nitride layer being 50-200 nm thick. By precisely controlling these dimensional parameters and their ratio, the invention achieves optimal balance between charge mobility enhancement and electrical uniformity maintenance.

Inventive Principle:

Principle #35Parameter changes

2Speed

If polysilicon TFT is used, then charge mobility increases, but achieving uniformity over large-sized display devices becomes difficult

Engineering Contradiction:

Improvecharge mobilityVSAvoiduniformity in electrical characteristics

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent employs a composite gate insulating layer structure combining silicon oxide and silicon nitride layers. The silicon oxide layer provides good interface characteristics with the semiconductor layer, while the silicon nitride layer contributes to stable electrical properties and reduced defect density. This composite structure enables both high charge mobility and uniform electrical characteristics across large display areas.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent optimizes the thickness parameters of the gate insulating layer components, with the silicon oxide layer being 50-150 nm thick and the silicon nitride layer being 50-200 nm thick. By precisely controlling these dimensional parameters and their ratio, the invention achieves optimal balance between charge mobility enhancement and electrical uniformity maintenance.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If conventional gate insulating layers are used, then manufacturing is simple, but electrical characteristics uniformity deteriorates

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidelectrical characteristics uniformity

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent employs a composite gate insulating layer structure combining silicon oxide and silicon nitride layers. The silicon oxide layer provides good interface characteristics with the semiconductor layer, while the silicon nitride layer contributes to stable electrical properties and reduced defect density. This composite structure enables both high charge mobility and uniform electrical characteristics across large display areas.

Inventive Principle:

Principle #40Composite materials

Data Source

PatentUS9954006B2Thin film transistor array substrate and method of manufacturing the same

Publication Date: 2018.04.24 SAMSUNG DISPLAY CO LTD

AI summary

A TFT array substrate includes a semiconductive oxide layer disposed on an insulating substrate and including a channel portion, a gate electrode overlapping the semiconductive oxide layer, a gate insulating layer interposed between the semiconductive oxide layer and the gate electrode, and a passivation layer disposed on the semiconductive oxide layer and the gate electrode. At least one of the gate insulating layer and the passivation layer includes an oxynitride layer, and the oxynitride layer has a higher concentration of oxygen than that of nitrogen in a location of the oxynitride layer closer to the semiconductive oxide layer.