Lateral-Junction Photodiode with Oxide Semiconductor Transistor
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Solution Overview
Problem
Current semiconductor devices with photosensors face challenges in achieving high accuracy and sensitivity in light detection due to limitations in light-receiving area and leakage current.
Innovation Solution
The use of a semiconductor device with a lateral-junction photodiode and transistors, including an oxide semiconductor for reduced leakage current and increased light-receiving area, along with light-transmitting wiring to enhance light sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the light-receiving area is increased to improve light sensitivity, then the accuracy of light detection is improved, but the device area or circuit layout complexity increases
Solution Approach 1:
The patent merges the light-receiving element with the transistor structure by allowing the n-region or p-region of the photodiode to overlap with the transistor body. This integration allows the transistor to serve dual purposes: circuit functionality and light reception, thereby increasing the effective light-receiving area without proportionally increasing the overall device area.
Solution Approach 2:
The patent utilizes vertical stacking and overlapping in the third dimension (depth) rather than only expanding in the planar area. By forming the light-receiving element and transistors in overlapping vertical layers, the design increases light-receiving area without linearly increasing the device footprint, effectively using dimensional transition to resolve the area constraint.
2Measurement precision
If oxide semiconductor is used for the first transistor to reduce leakage current, then the accuracy of light detection is improved, but the manufacturing complexity or material selection constraints increase
Solution Approach 1:
The patent changes the material parameter of the transistor from conventional semiconductor to oxide semiconductor. This material substitution fundamentally alters the electrical characteristics, particularly reducing leakage current in the off state, which directly improves light detection accuracy by minimizing signal noise.
Solution Approach 2:
The patent employs a composite material structure where oxide semiconductor is specifically used for the first transistor while other components may use different materials. This selective material composition optimizes each component's performance: oxide semiconductor for low leakage, silicon for high-speed photodetection, achieving overall system improvement through material diversity.
3Measurement precision
If wiring over the light-receiving region is made of light-transmitting material, then the light-receiving area is increased, but the electrical conductivity or wiring design complexity increases
Solution Approach 1:
The patent applies different material properties to different regions: light-transmitting materials are used specifically for wirings located over the light-receiving region, while conventional conductive materials can be used in other areas. This localized material selection ensures optical transparency where needed while maintaining overall electrical performance.
Solution Approach 2:
The patent changes the optical parameter (transparency) of the wiring material for specific regions. By selecting materials with appropriate optical transmission properties for wirings over the light-receiving area, the design allows light to pass through to the photodiode while still providing necessary electrical connectivity, thus increasing effective light-receiving area without compromising circuit function.
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 improves light detection accuracy and sensitivity by increasing the light-receiving area and reducing leakage current, enabling high-accuracy light detection.
Implementation Method 1
a light-receiving element which converts light into an electric signal
Implementation Method 2
an oxide semiconductor is used for the first transistor which transfers an electric signal, resulting in a reduction in the leakage current of the first transistor in the off state
Data Source
AI summary
An object of the invention is to improve the accuracy of light detection in a photosensor, and to increase the light-receiving area of the photosensor. The photosensor includes: a light-receiving element which converts light into an electric signal; a first transistor which transfers the electric signal; and a second transistor which amplifies the electric signal. The light-receiving element includes a silicon semiconductor, and the first transistor includes an oxide semiconductor. The light-receiving element is a lateral-junction photodiode, and an n-region or a p-region included in the light-receiving element overlaps with the first transistor.