Avalanche Photodiode Through-Electrode Spatial Separation
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Solution Overview
Problem
Existing photodetecting devices face challenges in achieving both high photodetection accuracy and resolution due to limitations in pixel size and pitch, which affect photosensitivity and time responsiveness, especially when using through-electrodes for signal reading.
Innovation Solution
A semiconductor substrate configuration with separate areas for avalanche photodiodes and through-electrodes, where the photodiodes are distributed in one direction and the through-electrodes are distributed two-dimensionally orthogonal to the photodiodes, allowing for reduced pixel pitch without compromising signal reading efficiency and minimizing parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pitch between pixels is reduced to improve photodetection resolution, then the photodetection resolution is improved, but the photodetection accuracy decreases due to lower photosensitivity
Solution Approach 1:
The patent separates the distribution of avalanche photodiodes (in the first direction) from the distribution of through-electrodes (two-dimensional distribution in orthogonal directions). This spatial separation in different dimensions allows pixel pitch to be reduced for higher resolution while maintaining adequate spacing for through-electrodes to ensure photosensitivity and prevent signal reading issues.
Solution Approach 2:
The semiconductor substrate is divided into distinct functional areas: a first area for distributing avalanche photodiodes in the first direction, and a second area for two-dimensional distribution of through-electrodes. This segmentation allows independent optimization of photodetection resolution (via photodiode spacing) and photosensitivity (via through-electrode spacing).
2Ease of operation
If through-electrodes are used to read signals from avalanche photodiodes, then signal reading is achieved, but the pitch between pixels is limited due to required arrangement area for through-electrodes
Solution Approach 1:
The patent transitions from co-located through-electrode arrangement to separated two-dimensional distribution in orthogonal directions. This allows through-electrodes to maintain adequate spacing for reliable signal reading while enabling smaller pixel pitch, thus improving photodetection resolution without compromising signal reading capability.
3Measurement precision
If bonding wires are used to read signals from avalanche photodiodes with small pitch, then signal reading is achieved, but time responsiveness decreases and noise is generated due to parasitic capacitance between wires
Solution Approach 1:
The patent extracts the signal reading function from bonding wires and implements it through through-electrodes that penetrate the semiconductor substrate. This eliminates parasitic capacitance between bonding wires, preventing noise generation and maintaining time responsiveness, while still enabling small pixel pitch for high photodetection resolution.
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 enhances photodetection accuracy and resolution by ensuring sufficient space for through-electrodes, reducing parasitic capacitance, and improving time responsiveness while maintaining high photosensitivity.
Implementation Method 1
a plurality of avalanche photodiodes arranged to operate in Geiger mode
Implementation Method 2
Avalanche photodiodes arranged to operate in Geiger mode has a much higher photosensitivity than generally-available photodiodes having the same pixel size because a reverse voltage equal to or more than the breakdown voltage is applied to the avalanche photodiode
Data Source
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AI summary
A photodetecting device includes a semiconductor substrate including a first principal surface and a second principal surface that oppose each other and a plurality of through-electrodes penetrating through the semiconductor substrate in a thickness direction. The semiconductor substrate includes a plurality of avalanche photodiodes arranged to operate in Geiger mode. The plurality of through-electrodes are electrically connected to the corresponding avalanche photodiodes. The semiconductor substrate includes a first area in which the plurality of avalanche photodiodes are distributed in at least a first direction and a second area in which the plurality of through-electrodes are distributed two-dimensionally. The first area and the second area are distributed in a second direction orthogonal to a first direction when viewed from a direction orthogonal to the first principal surface.