SPAD Photodetector Trench Shielding for Lower Capacitance
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Solution Overview
Problem
Existing photodetection devices face challenges in reducing power consumption, particularly in devices utilizing single photon avalanche diodes (SPADs), which tend to increase power consumption due to high capacitance and dark current.
Innovation Solution
The photodetection device incorporates a trench with a light-shielding film made of metal and a first wiring of polycrystalline or amorphous silicon that connects the anode electrode to the light-shielding film, reducing capacitance and dark current, thereby minimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a light-receiving element with high capacitance is used to improve light reception sensitivity, then detection capability is improved, but power consumption increases
Solution Approach 1:
The patent segments the capacitance-reducing function into a dedicated trench structure with light-shielding film, separating it from the light-receiving element itself. This allows the light-receiving element to maintain high capacitance for sensitivity while the trench structure provides capacitance reduction and dark current suppression, resolving the contradiction between detection capability and power consumption.
Solution Approach 2:
The trench structure with light-shielding film acts as an intermediary element between the light-receiving element and the surrounding environment. It mediates by providing electrical connection while simultaneously reducing capacitance and blocking stray light, enabling the light-receiving element to operate at optimal sensitivity without excessive power consumption.
2Reliability
If the anode electrode is positioned close to the light-receiving element to improve electrical connection, then connectivity is improved, but capacitance increases and dark current rises
Solution Approach 1:
The patent applies local quality by creating a specialized trench structure with light-shielding film at the specific location where the anode electrode connects to the light-receiving element. This localized structure provides excellent electrical connection while simultaneously suppressing dark current and reducing capacitance, resolving the contradiction between connectivity and dark current generation.
Solution Approach 2:
The patent moves the electrical connection from a planar two-dimensional arrangement to a three-dimensional trench structure. By connecting the anode electrode through the trench from a different spatial dimension, it achieves reliable electrical connection while maintaining sufficient distance to reduce capacitance and prevent dark current, thus resolving the contradiction between connectivity and harmful effects.
3Object-affected harmful factors
If a metal light-shielding film is used to block stray light, then light shielding performance is improved, but device complexity increases
Solution Approach 1:
The patent makes the trench structure multi-functional by combining light-shielding, electrical connection, and capacitance reduction functions into a single integrated structure. The light-shielding film within the trench simultaneously blocks stray light while the trench itself provides the electrical connection path and capacitance reduction, eliminating the need for separate components and reducing overall device complexity despite the added light-shielding capability.
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 power consumption while maintaining device performance by minimizing capacitance and dark current, allowing for stable voltage supply and wider area for reading circuits, thus achieving high-performance photodetection.
Implementation Method 1
a light-receiving element configured to receive light and output a current
Implementation Method 2
a light-shielding film provided in the trench, the light-shielding film including a metal material
Implementation Method 3
a first wiring provided on a first surface side of the first semiconductor layer. The first wiring includes polycrystalline silicon or amorphous silicon and electrically connects the first semiconductor region and the light-shielding film
Data Source
AI summary
A photodetection device according to one embodiment of the present disclosure includes: a first semiconductor layer including a light-receiving element configured to receive light and output a current; a trench provided in the first semiconductor layer, the trench surrounding the light-receiving element; a light-shielding film provided in the trench, the light-shielding film including a metal material; and a first wiring provided on a first surface side of the first semiconductor layer. The light-receiving element includes a first semiconductor region of first conductivity type and a second semiconductor region of second conductivity type that are provided on the first surface side of the first semiconductor layer. The first wiring includes polycrystalline silicon or amorphous silicon and electrically connects the first semiconductor region and the light-shielding film.