Oxide Semiconductor Display Insulating Layer Segmentation

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Solution Overview

Problem

Display devices using oxide semiconductor transistors in both pixel and driver circuits face reliability issues due to moisture and hydrogen ingress, leading to variations in electrical characteristics, especially in high temperature and high humidity environments.

Innovation Solution

A display device structure is implemented where a pixel portion includes multiple insulating layers, including a first inorganic layer covering the pixel transistor, a second organic layer for planarization, and a third inorganic layer, while the driver circuit portion only has the first and third inorganic layers, preventing moisture and hydrogen from entering the oxide semiconductor layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Shape

If an organic insulating layer is formed over the oxide semiconductor layer to reduce unevenness, then the planarization is improved, but moisture and hydrogen from the organic material enter the oxide semiconductor layer causing carrier density increase and threshold voltage shift

Engineering Contradiction:

ImproveplanarizationVSAvoidelectrical characteristic stability

Core Design Contradiction:

ShapeVSReliability

Solution Approach 1:

The insulating layer structure is segmented into multiple distinct layers: an inorganic insulating layer directly contacting the oxide semiconductor layer to provide barrier protection, and an organic insulating layer positioned above to provide planarization. This segmentation allows each layer to perform its specialized function without interfering with the other's primary role.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The inorganic insulating layer acts as an intermediary barrier between the organic insulating layer and the oxide semiconductor layer. It prevents harmful impurities (moisture and hydrogen) from the organic layer from reaching the sensitive oxide semiconductor layer, while still allowing the organic layer to perform its planarization function.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If multiple insulating layers are formed to prevent impurity entry, then reliability is improved, but device complexity increases

Engineering Contradiction:

Improvetransistor performance stabilityVSAvoidinsulating layer structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The protective inorganic insulating layer is applied selectively only in regions where oxide semiconductor transistors are formed, rather than uniformly across the entire substrate. This localized approach provides necessary protection where needed while minimizing unnecessary structural complexity in other areas.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS9659968B2Display device comprising a metal oxide semiconductor channel and a specified insulating layer arrangement

Publication Date: 2017.05.23 SEMICON ENERGY LAB CO LTD

AI summary

Variation in the electrical characteristics of transistors is minimized and reliability of the transistors is improved. A display device includes a pixel portion 104 and a driver circuit portion 106 outside the pixel portion. The pixel portion includes a pixel transistor, a first insulating layer 122 which covers the pixel transistor and includes an inorganic material, a second insulating layer 124 which is over the first insulating layer and includes an organic material, and a third insulating layer 128 which is over the second insulating layer and includes an inorganic material. The driver circuit portion includes a driving transistor for supplying a signal to the pixel transistor, and the first insulating layer covering the driving transistor. The second insulating layer is not formed in the driver circuit portion.