Oxide Semiconductor TFTs for Display Devices

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Solution Overview

Problem

The existing display devices require multiple masks for manufacturing, increasing costs, and suffer from damage to the oxide semiconductor layer during etching, which hampers the improvement of electrical characteristics of thin film transistors (TFTs).

Innovation Solution

A display device design where pixel-driving TFTs have an oxide semiconductor active layer covering the separation section between source and drain electrodes, and driver circuit TFTs use a non-oxide semiconductor active layer, eliminating the need for an etching stopper layer and reducing the number of masks required, thereby lowering manufacturing costs and enhancing electrical characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If an etching stopper layer is provided on the oxide semiconductor layer, then damage to the oxide semiconductor layer during etching is prevented, but the number of masks increases and manufacturing cost increases

Engineering Contradiction:

Improvedamage prevention to oxide semiconductor layerVSAvoidnumber of masks

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The invention extracts and removes the etching stopper layer from the conventional structure. By forming the oxide semiconductor layer to directly cover the source and drain electrodes without an intermediate etching stopper layer, the patent eliminates the need for this protective layer while still preventing damage to the oxide semiconductor layer during etching processes.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of adding a protective layer on top of the oxide semiconductor layer to prevent damage, the invention inverts the approach by having the oxide semiconductor layer itself serve as the protective element by directly covering the electrodes. This reversal of the conventional protective layer approach eliminates the need for additional masks and process steps.

Inventive Principle:

Principle #13The other way round (Inversion)

2Device complexity

If an etching stopper layer is not provided, then the number of masks is reduced and manufacturing cost is lowered, but heavy damage to the oxide semiconductor layer by etching is unavoidable

Engineering Contradiction:

Improvenumber of masksVSAvoiddamage to oxide semiconductor layer

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The oxide semiconductor layer is formed in advance to directly cover the source and drain electrodes before the etching process. This preliminary protective coverage prevents etching damage to the oxide semiconductor layer without requiring an additional etching stopper layer, thus reducing the number of masks needed.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The oxide semiconductor layer serves a dual function: as the active semiconductor layer and as a protective layer during etching. By having the oxide semiconductor layer directly cover the electrodes, it protects itself and the underlying structure from etching damage without requiring a separate protective layer.

Inventive Principle:

Principle #25Self-service

3Reliability

If pixel-driving TFTs use oxide semiconductor active layer, then off leakage current is greatly reduced, but manufacturing complexity increases due to additional masks

Engineering Contradiction:

Improveoff leakage currentVSAvoidmanufacturing process

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The invention extracts and removes the etching stopper layer from the manufacturing process, thereby reducing the number of masks required. This simplification is achieved while maintaining the oxide semiconductor active layer structure that provides low off leakage current, thus reducing manufacturing complexity without sacrificing reliability.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention merges the function of the oxide semiconductor layer with the protective function previously provided by a separate etching stopper layer. By having the oxide semiconductor layer directly cover the source and drain electrodes, it combines the active semiconductor function with the protective function, eliminating the need for additional masks and simplifying the manufacturing process.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS10438973B2Display device and method for manufacturing same

Publication Date: 2019.10.08 SHARP KK

AI summary

This display device is provided with: a circuit substrate having a display region and a non-display region; pixel-driving TFTs for driving pixels, formed in the display region and having source electrodes and drain electrodes being spaced apart from each other on an insulating film and a first active layer formed from an oxide semiconductor, provided on the opposite side from the insulating film so as to cover a separation section between a source electrode and a drain electrode and part of the source electrode and part of the drain electrode adjacent to the separation section; and a driver circuit TFT for driving the pixel-driving TFTs, formed in the non-display region and having a second active layer formed from a non-oxide semiconductor.