Transparent Storage Capacitor in Oxide Semiconductor TFTs
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Solution Overview
Problem
The use of metal film gate wiring for storage capacitor electrodes in TFT substrates for liquid crystal display apparatuses leads to a decrease in aperture ratio and light transmittance, complicating the production process and limiting the formation of storage capacitors within pixels.
Innovation Solution
A semiconductor device with a thin-film transistor and a metal oxide layer containing indium, tin, and zinc, where the transparent conductive layer overlaps the conductor region of the metal oxide layer, allowing for the formation of a transparent storage capacitor with reduced resistance, thereby maintaining high aperture ratio and transmittance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal film is used for storage capacitor electrodes, then electrical conductivity is improved, but aperture ratio and light transmittance deteriorate
Solution Approach 1:
The patent changes the material parameter from metal film to transparent conductive oxide film (such as ITO, IZO, or In-Sn-Zn-O), which maintains electrical conductivity while being transparent. This material substitution allows the storage capacitor electrodes to remain electrically functional while enabling light transmission, thereby resolving the contradiction between conductivity and transmittance.
Solution Approach 2:
The patent employs composite material structures where transparent conductive oxide layers are combined with insulating layers (such as silicon oxide or silicon nitride) to form the storage capacitor. This composite approach achieves both electrical functionality and optical transparency, allowing the storage capacitor to be formed within the pixel area without blocking light.
2Reliability
If metal film is used for storage capacitor electrodes, then electrical conductivity is improved, but production process complexity increases
Solution Approach 1:
The transparent conductive oxide film serves multiple functions: it acts as both the storage capacitor electrode and maintains electrical connectivity, while also being transparent for display purposes. This multi-functionality eliminates the need for separate metal film layers, simplifying the production process while maintaining conductivity requirements.
Solution Approach 2:
By changing from metal film deposition to transparent conductive oxide deposition, the patent utilizes deposition processes that are already established in oxide semiconductor TFT manufacturing, thereby avoiding additional process complexity while achieving the required electrical conductivity.
3Reliability
If storage capacitor area is increased, then capacitance is improved, but aperture ratio deteriorates
Solution Approach 1:
The patent uses thin film structures for the storage capacitor, allowing the capacitor to be formed in a planar configuration within the pixel area. The thin film nature enables high capacitance density, achieving sufficient storage capacitance without occupying excessive pixel area, thus maintaining high aperture ratio.
Solution Approach 2:
By forming the storage capacitor using transparent conductive oxide and insulating material composites, the patent achieves high capacitance within the available pixel area. The composite structure allows optimized capacitance density while maintaining transparency, enabling sufficient storage capacitance without sacrificing 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 solution enables the formation of storage capacitors with low electric resistance and high transmittance, improving the aperture ratio and simplifying the production process by using a transparent material for the storage capacitor electrodes.
Implementation Method 1
the oxide semiconductor layer and the metal oxide layer contain indium, tin, and zinc, and the transparent conductive layer overlaps at least a portion of the conductor region with the interlayer insulating layer therebetween
Data Source
AI summary
A semiconductor device (1001) includes a thin-film transistor (101) including a gate electrode (3), an oxide semiconductor layer (7), a gate insulating layer (5), a source electrode (9s), and a drain electrode (9d); a metal oxide layer (8) including a conductor region (70c) and formed from an oxide film from which the oxide semiconductor layer (7) is also formed; an interlayer insulating layer (13) covering the thin-film transistor and the metal oxide layer (8); and a transparent conductive layer (15) disposed on the interlayer insulating layer and electrically connected to the drain electrode, wherein the oxide semiconductor layer (7) and the metal oxide layer (8) contain indium, tin, and zinc, and the transparent conductive layer (15) overlaps at least a portion of the conductor region (70c) with the interlayer insulating layer (13) therebetween.