Oxide Semiconductor Display Device Light Protection
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Solution Overview
Problem
Existing display devices using oxide semiconductors face degradation issues due to external light exposure, leading to variations in threshold voltage, which can affect image display quality, and previous methods for forming protective layers either decrease manufacturing throughput or result in undesirable characteristics.
Innovation Solution
A display device structure incorporating a gate electrode, gate insulating film, oxide semiconductor layer, channel protective layer, and source/drain electrodes, with a metal oxide layer formed on top of the channel protective layer to prevent light-induced degradation, and an etching stopper layer with contact holes for source/drain electrodes, enhancing reliability and manufacturing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer including titanium oxide or titanium oxynitride is formed using a direct current reactive sputtering method, then the protective layer can effectively function to prevent light-induced degradation, but the thickness must be sufficiently large which decreases manufacture throughput
Solution Approach 1:
The patent changes the formation method parameter from direct current reactive sputtering to alternating current sputtering. This parameter change allows the protective layer to be formed with sufficient thickness while maintaining manufacturing throughput, as AC sputtering enables better control of the deposition process and reduces the time required to form an effective protective layer compared to DC sputtering.
2Reliability
If an oxidation process is performed after formation of a pattern including titanium or titanium alloys on the upper part of the oxide semiconductor layer, then oxide titanium can be formed, but oxygen in the oxide semiconductor layer is absorbed and lost in the process resulting in difficulty in obtaining preferable characteristics
Solution Approach 1:
The patent applies preliminary action by forming the protective layer directly during the sputtering process rather than through a subsequent oxidation process. The protective layer is formed with appropriate oxygen content inherent to the sputtering deposition, eliminating the need for post-formation oxidation that would cause oxygen loss from the oxide semiconductor layer. This preliminary formation approach preserves the oxygen content and electrical characteristics of the oxide semiconductor layer.
3Reliability
If a thick protective layer is formed to effectively prevent light-induced degradation, then reliability improves, but the aperture ratio of the display device decreases
Solution Approach 1:
The patent changes the formation method parameter to alternating current sputtering, which enables the formation of a protective layer with sufficient thickness for light protection while achieving better coverage efficiency. The AC sputtering process allows for optimized deposition rates and uniform thickness distribution, providing effective light blocking with a thinner layer compared to DC sputtering, thereby maintaining a higher aperture ratio.
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 proposed solution effectively suppresses light-induced threshold voltage shifts, maintaining high reliability and aperture ratio while reducing power consumption, enabling high-performance and cost-effective manufacturing of liquid crystal display devices.
Implementation Method 1
a metal oxide layer which is formed on an upper part of the channel protective layer... effectively suppresses light-induced threshold voltage shifts
Implementation Method 2
Japanese Unexamined Patent Publication No. 2010-161373 discloses a technique for forming a protective layer including titanium oxide or titanium oxynitride, using a direct current reactive sputtering method
Implementation Method 3
Japanese Unexamined Patent Publication No. 2010-283326 discloses a technique for forming oxide titanium, by performing an oxidation process, after formation of a pattern including titanium or titanium alloys
Data Source
AI summary
Provided are a reliable high performance thin film transistor and a reliable high performance display device. The display device has: a gate electrode which is formed on a substrate; a gate insulating film which is formed to cover the substrate and the gate electrode; an oxide semiconductor layer which is formed on the gate electrode through the gate insulating film; a channel protective layer which is in contact with the oxide semiconductor layer and formed on the oxide semiconductor layer; and source/drain electrodes which are electrically connected to the oxide semiconductor layer and formed to cover the oxide semiconductor layer. A metal oxide layer is formed on an upper part of the channel protective layer. The source/drain electrodes are formed to be divided apart on the channel protective layer and the metal oxide layer.