Oxide Semiconductor Non-Linear Element for Display Protective Circuit
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Solution Overview
Problem
Existing display devices using thin film transistors face challenges in achieving high field effect mobility and reliable operation at low temperatures, with amorphous silicon transistors having low mobility and polycrystalline silicon transistors requiring costly crystallization steps, while also occupying significant area due to complex protective circuits.
Innovation Solution
A display device structure incorporating a non-linear element with oxide semiconductors of varying oxygen content, where the second oxide semiconductor layer with higher conductivity is directly connected to the gate electrode or conductive film, reducing contact resistance and area occupancy by minimizing interfaces and contact holes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If amorphous silicon is used for thin film transistor, then larger substrate area can be covered, but field effect mobility is low
Solution Approach 1:
The patent changes the material parameter from amorphous silicon to oxide semiconductor, which fundamentally alters the electrical properties and enables high field effect mobility while maintaining compatibility with large substrate areas and low temperature processing
Solution Approach 2:
The patent uses composite oxide semiconductor materials with specific compositions (e.g., In-Ga-Zn-O) that combine the advantages of different materials to achieve both high mobility and manufacturability on large substrates
2Reliability
If polycrystalline silicon is used for thin film transistor, then field effect mobility is high, but crystallization step such as laser annealing is necessary
Solution Approach 1:
The patent changes the processing temperature parameter from high temperature (required for polycrystalline silicon crystallization) to low temperature (room temperature to 300°C), enabling simple manufacturing processes while maintaining high field effect mobility through oxide semiconductor materials
Solution Approach 2:
The patent replaces expensive and complex laser annealing processes with simpler, more cost-effective low temperature deposition and annealing methods, making the manufacturing process more accessible and scalable
3Reliability
If protective circuit is added to display device, then operational reliability is improved, but area occupied by protective circuit increases
Solution Approach 1:
The patent merges the protective circuit functionality with the existing pixel portion structures by using the same oxide semiconductor material system and fabrication processes, allowing the protective circuit to be integrated without requiring additional dedicated area
Solution Approach 2:
The patent creates universal oxide semiconductor-based transistor structures that can serve multiple functions - both as pixel switching elements and as protective circuit elements - thereby eliminating the need for separate protective circuit areas
Data Source
AI summary
A display device including an oxide semiconductor, a protective circuit and the like having appropriate structures and a small occupied area is necessary. The protective circuit is formed using a non-linear element which includes a gate insulating film covering a gate electrode; a first oxide semiconductor layer which is over the gate insulating layer and overlaps with the gate electrode; and a first wiring layer and a second wiring layer each of which is formed by stacking a conductive layer and a second oxide semiconductor layer and whose end portions are over the first oxide semiconductor layer and overlap with the gate electrode. The gate electrode of the non-linear element is connected to a scan line or a signal line, the first wiring layer or the second wiring layer of the non-linear element is directly connected to the gate electrode layer so as to apply potential of the gate electrode.