Light Sensing Unit Layout for High-Resolution Signal Detection
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Solution Overview
Problem
As light sensing devices require higher resolution, reducing the size of light sensing elements decreases the light-receiving area, leading to a lower signal-to-noise ratio and image definition, particularly in applications like fingerprint detection.
Innovation Solution
A light sensing unit with a light sensing element and a switching element, where at least one of the source and drain is formed of a light-transmissive conductive layer, allowing increased light penetration and absorption, and a gate structure that overlaps one source or drain but not the other, enhancing the light-receiving area and signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the size of light sensing elements is reduced to increase density, then the resolution is improved, but the light-receiving area is reduced
Solution Approach 1:
The gate electrode is positioned offset from the center of the light sensing element, creating an asymmetric overlap configuration. This dimensional arrangement allows the gate to overlap one source/drain region while leaving the other source/drain region fully exposed to incident light, thereby maintaining adequate light-receiving area even as element size is reduced for higher resolution.
Solution Approach 2:
The light-transmissive conductive layer is selectively applied only to the source or drain region that is not overlapped by the gate electrode. This localized application ensures that the critical light-receiving area maintains high transmissivity while the gate overlap region provides necessary electrical functionality, optimizing both resolution and light reception locally.
2Manufacturing precision
If the size of light sensing elements is reduced to increase density, then the resolution is improved, but the signal-to-noise ratio is reduced
Solution Approach 1:
By positioning the gate electrode offset in the planar dimension rather than centered, the design creates an asymmetric configuration where one source/drain region remains fully exposed. This dimensional arrangement preserves adequate light-receiving area, maintaining signal strength and thus signal-to-noise ratio even as overall element size is reduced for higher resolution.
Solution Approach 2:
The light-transmissive conductive layer is selectively applied to the non-overlapped source or drain region, ensuring that the critical light-receiving area maintains high transmissivity. This localized optimization preserves signal quality and signal-to-noise ratio while allowing element size reduction for improved resolution.
3Reliability
If a conventional gate structure overlapping both source and drain is used, then the transistor control is improved, but the light-receiving area is reduced
Solution Approach 1:
The gate electrode is positioned offset in the planar dimension, creating an asymmetric configuration where it overlaps one source/drain region but not the other. This dimensional repositioning maintains sufficient gate control over the channel while preserving a larger light-receiving area in the non-overlapped region, resolving the trade-off between transistor control and light reception.
Solution Approach 2:
The light-transmissive conductive layer is selectively applied to the source or drain region that is not overlapped by the gate, ensuring high light transmissivity in the critical light-receiving area. This localized approach maintains adequate transistor control through gate overlap while maximizing light reception in the exposed region.
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 improves the signal-to-noise ratio and maintains image definition even at higher resolutions, enabling effective detection of light intensity and greyscale values, such as in fingerprint recognition.
Implementation Method 1
at least one of the first source and the first drain is formed of a light-transmissive conductive layer
Data Source
AI summary
The present invention discloses a light sensing unit of a light sensing device including a light sensing element and a switching element. The light sensing element includes a gate, a semiconductor layer, a gate insulating layer, a source, and a drain. The gate and the semiconductor layer are disposed on a substrate, the gate insulating layer separates the gate from the semiconductor layer, and the source and the drain are connected to the semiconductor layer respectively. At least one of the source and the drain are formed of a light-transmissive conductive layer. The semiconductor layer is disposed between one of the source and the drain and the gate, and when viewed along a normal direction of the substrate, the gate overlaps the one of the source and the drain, and the gate does not overlap another one of the source and the drain.