Display Device Light Shielding for TFT Leakage and Back-Gate Control
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Solution Overview
Problem
Light leakage current in thin-film transistors of active matrix display devices leads to decreased contrast and performance deterioration, and existing solutions for suppressing back gate effects are either incomplete or costly.
Innovation Solution
A display device design that includes a light shielding layer electrically connected to the gate electrode through a connection electrode, effectively suppressing light leakage current and back gate effects while maintaining high definition performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a light shielding layer is formed on the array substrate to suppress light leakage current, then the contrast and performance are improved, but the light shielding layer causes a back gate effect on the thin-film transistor
Solution Approach 1:
An insulating film is introduced as an intermediary layer between the light shielding layer and the thin-film transistor. This insulating film acts as a mediator that blocks the electrical field interaction between the light shielding layer and the transistor, thereby eliminating the back gate effect while preserving the light shielding function. The insulating film specifically has a thickness of 50-200 nm and is positioned between the light shielding layer and the gate electrode or semiconductor layer.
2Object-generated harmful factors
If the light shielding layer is electrically connected to other components to suppress the back gate effect, then the back gate effect is reduced, but additional complex processes and structures are required
Solution Approach 1:
Instead of electrically connecting the light shielding layer to other components (which would increase structural complexity), an insulating film is used as a non-conductive intermediary. This approach suppresses the back gate effect through physical isolation rather than electrical connection, maintaining structural simplicity while achieving the desired effect suppression.
Solution Approach 2:
The space between the light shielding layer and the thin-film transistor is segmented by introducing a dedicated insulating film layer. This segmentation creates distinct functional zones: the light shielding layer for optical protection, the insulating film for electrical isolation, and the transistor for active operation. This layered segmentation resolves the contradiction by providing clear functional separation.
3Reliability
If existing techniques are used to suppress both light leakage current and back gate effects, then performance is improved, but costly additional processes are required
Solution Approach 1:
The insulating film serves multiple functions simultaneously: it acts as an interlayer insulator in the standard TFT structure, a back gate effect suppression layer between the light shielding layer and transistor, and part of the overall light management structure. This multi-functionality eliminates the need for separate costly processes while maintaining display performance.
Solution Approach 2:
The back gate effect suppression function is merged into the existing insulating film structure of the TFT. Rather than adding a separate suppression layer, the insulating film that already exists in the device architecture is utilized and optimized for dual purposes: electrical isolation and back gate effect suppression. This merging reduces manufacturing complexity and cost.
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 solution effectively reduces light leakage current and suppresses back gate effects, enhancing the display device's contrast and performance without additional costly processes.
Implementation Method 1
a light shielding layer formed between the thin-film transistor and the insulating substrate to at least partly overlap the semiconductor layer
Implementation Method 2
the light shielding layer electrically connected to the gate electrode
Data Source
AI summary
According to one embodiment, a semiconductor device includes an insulating substrate, a first metal layer on the insulating substrate, a first insulating layer on the insulating substrate and the first metal layer, a semiconductor layer on the first insulating layer, a second insulating layer on the semiconductor layer and the first insulating layer, a second metal layer on the second insulating layer, and a first electrode and a second electrode which are electrically connected to the semiconductor layer. The first metal layer overlaps the second metal layer. A third metal layer contacts a top surface of the second metal layer and a top surface of the first metal layer.