TFT Substrate Transparent Oxide Film Conductive Region Design
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Solution Overview
Problem
The manufacturing of TFT substrates for LCDs, particularly in the FFS mode, requires multiple photolithography processes, increasing costs and complexity due to the use of oxide semiconductor films that are easily dissolved by acid solutions used for etching metal films, and the need for special processes to enhance electrical conductivity and resistance.
Innovation Solution
A thin film transistor substrate design that includes a gate electrode, common electrode, transparent oxide film, and light transmissive pixel electrode, where the transparent oxide film forms a conductive region and semiconductor region, allowing for reduced photolithography processes and improved electrical characteristics by oxidizing the oxide film to increase resistance and maintain conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If oxide semiconductor films are used for TFT active layers, then light transmittance and electrical mobility are improved, but the films are easily dissolved by acid solutions used for etching metal films
Solution Approach 1:
The patent applies preliminary action by forming a protective film (such as silicon nitride or silicon oxide) on the oxide semiconductor film before the metal film etching process. This protective film is deposited in advance to prevent the oxide semiconductor from being dissolved by the acid solution during subsequent etching steps, thereby resolving the contradiction between maintaining light transmittance and ensuring etching resistance.
2Manufacturing precision
If multiple photolithography processes are used for FFS mode TFT substrates, then manufacturing precision is improved, but device complexity and manufacturing costs increase
Solution Approach 1:
The patent merges multiple photolithography processes into fewer steps by designing a structure where the pixel electrode and common electrode are formed in the same oxide semiconductor layer. This allows simultaneous patterning of both electrodes, reducing the number of separate photolithography processes while maintaining the precision required for FFS mode operation.
Solution Approach 2:
The oxide semiconductor layer serves multiple functions: it acts as the active layer for the TFT, the material for the pixel electrode, and the material for the common electrode. This multi-functionality reduces the number of separate fabrication processes needed, thereby simplifying device complexity while maintaining manufacturing precision.
3Productivity
If oxide semiconductor films are used, then productivity is improved through reduced processes, but electrical conductivity control becomes more difficult
Solution Approach 1:
The patent controls electrical conductivity by changing parameters such as the thickness of the oxide semiconductor film, its composition (ratios of metal oxides), and post-deposition treatment conditions. By adjusting these parameters, the conductivity can be precisely controlled to meet TFT requirements while maintaining the productivity benefits of reduced process steps.
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
This design reduces the number of photolithography processes, lowers manufacturing costs, and enhances the electrical performance of the TFT substrate, enabling high-definition and high-quality display with improved productivity and reliability.
Implementation Method 1
oxidizing the oxide film to increase resistance and maintain conductivity
Data Source
AI summary
A thin film transistor substrate includes: a gate insulating film that covers a gate electrode and a common electrode; a transparent oxide film selectively disposed on the gate insulating film; a source electrode and a drain electrode that are spaced from each other on the transparent oxide film; and a light transmissive pixel electrode electrically connected to the drain electrode. The transparent oxide film includes a conductive region and a semiconductor region. The conductive region is disposed in a lower portion of the source electrode and the drain electrode and disposed in a portion that continues from the lower portion of the drain electrode, extends to part of an upper portion of the common electrode, and forms the pixel electrode. The semiconductor region is disposed in a portion corresponding to a lower layer in a region between the source electrode and the drain electrode.