Oxide TFT Photodetector Layout for Low Leakage Current
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Solution Overview
Problem
Photodetectors with thin-film transistors (TFTs) suffer from increased leakage current due to damage during the process of forming the photodiode, particularly from dry etching, which is exacerbated by the use of oxide semiconductors.
Innovation Solution
The photodetector design includes a TFT with an oxide semiconductor film configured such that its width in a specific direction is smaller than the source and drain electrodes, reducing process damage and leakage current by minimizing the interface area with the gate insulating film, thereby stabilizing the threshold voltage against X-ray irradiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the oxide semiconductor film width is reduced to minimize process damage, then leakage current is reduced, but the interface area with the gate insulating film is also reduced
Solution Approach 1:
The oxide semiconductor film is designed with different width characteristics in different regions: it has a first width in the channel region and a second width in the source/drain regions, with the ratio controlled between 0.5-2.0. This local variation optimizes both leakage current reduction and interface area maintenance, resolving the technical contradiction by applying different dimensional characteristics to different functional regions of the same component.
2Manufacturing precision
If the oxide semiconductor film width is reduced to minimize process damage, then manufacturing precision is improved, but device complexity increases due to specific width ratio requirements
Solution Approach 1:
The patent establishes a specific parameter range for the width ratio (0.5-2.0) between the channel region and source/drain regions of the oxide semiconductor film. By defining this quantitative parameter range, the invention transforms a complex geometric design problem into a controllable parameter specification, making the manufacturing process more precise while managing device complexity through clear numerical bounds.
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 design achieves reduced leakage current and improved sensitivity by minimizing process damage to the TFT, maintaining stable threshold voltage even under ionizing radiation, thus enhancing the photodetector's performance.
Implementation Method 1
a photodiode configured to convert light into an electric charge
Data Source
AI summary
A photodetector includes: a photodiode configured to convert light into an electric charge; and a TFT configured to detect the electric charge. The TFT includes a gate electrode, a source electrode, a drain electrode, and an oxide semiconductor film. The oxide semiconductor film includes a first region overlapping the source electrode in a plan view, a second region overlapping the drain electrode in the plan view, and a third region located between the first region and the second region, and overlapping only the gate electrode in the plan view. In the plan view, a width of the oxide semiconductor film in a second direction is smaller than widths of the source and drain electrodes, the second direction being perpendicular to a first direction and perpendicular to the oxide semiconductor film, the first direction being a direction passing through the individual first, second, and third regions in a shortest distance.