Thin Film Transistor Array Substrate Contact Hole Configuration
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Solution Overview
Problem
The existing digital X-ray detectors suffer from high leakage current due to the formation of contact holes with large inclination angles, which affects the reliability and uniformity of the photodiode characteristics, especially when exposure and etching processes are not uniformly controlled.
Innovation Solution
The contact hole connecting the source electrode of the thin film transistor to the first electrode of the photodiode is formed outside the photodiode area, rather than in its lower part, to reduce leakage current and improve reliability by maintaining uniformity in leakage current characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If contact holes are formed with large inclination angles to connect source electrode to photodiode, then electrical connection is achieved, but leakage current increases and reliability deteriorates
Solution Approach 1:
The contact hole formation process is extracted and optimized independently. The patent applies specific etching conditions and inclination angle control to the contact hole formation step, separating it from other fabrication processes to achieve precise control over hole geometry and minimize leakage current paths.
Solution Approach 2:
The patent changes critical parameters including contact hole inclination angle, etching conditions, and formation timing. By optimizing these parameters, the contact hole geometry is controlled to reduce leakage current while maintaining reliable electrical connection between source electrode and photodiode.
2Ease of manufacture
If exposure and etching processes are not uniformly controlled, then manufacturing flexibility is maintained, but photodiode characteristic uniformity deteriorates
Solution Approach 1:
The contact holes are formed at predetermined positions and with predetermined inclination angles before final photodiode layer formation. This preliminary action ensures that subsequent manufacturing steps can proceed with standard processes while the critical connection geometry is already optimized, reducing variability in final photodiode characteristics.
3Reliability
If contact holes are formed in the lower part of photodiode, then electrical connection is achieved, but leakage current increases due to large inclination angles
Solution Approach 1:
The patent changes the spatial dimension and timing of contact hole formation. Instead of forming contact holes in the lower part of photodiode after standard layer formation, the method forms contact holes at predetermined positions with controlled inclination angles during a dedicated step, utilizing three-dimensional positioning control to minimize leakage paths while achieving electrical connection.
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 configuration effectively reduces leakage current and enhances the reliability of the digital photo-detector by forming the contact hole outside the photodiode area, minimizing variations in photodiode characteristics and maintaining uniformity despite variations in etching processes.
Implementation Method 1
a photodiode (PD) that detects an X-ray and outputs a detection signal... The photodiode (PD) is a device that converts incident light into an electrical detection signal through photoelectric effect
Data Source
AI summary
A thin film transistor array substrate for a digital photo-detector is provided. The thin film transistor array substrate includes a plurality of gate lines to supply a scan signal; a plurality of data lines to output data, the data lines arranged in a direction crossing the gate lines, wherein cell regions are defined by the gate lines and the data lines; a photodiode in each of the cell regions to perform photoelectric conversion; and a thin film transistor at each intersection between the gate lines and the data lines to turn on according to the scan signal of the gate lines and output the photoelectric conversion signal from the photodiode to the data lines. A contact area between a source electrode of the thin film transistor and a first electrode of the photodiode is at a portion outside an area covered by a photodiode region.