SPAD Pixel Avalanche Region Layout for Higher Light Sensitivity
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Solution Overview
Problem
The existing image sensors with a single photon avalanche diode (SPAD) structure face limitations in miniaturization and light-receiving sensitivity due to the contact between P-type and N-type semiconductor layers, hindering further improvement in pixel size and sensitivity.
Innovation Solution
A solid-state imaging element with an avalanche photodiode featuring a semiconductor region of one polarity with an annular structure and a hole at the center, and a semiconductor region of the second polarity positioned subsequent to the hole in the incident light direction, optimizing the electric field distribution for enhanced light reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the P-type semiconductor layer and N-type semiconductor layer are in contact with each other to form an avalanche region, then the image sensor can achieve signal multiplication through electron avalanche effect, but the pixel size cannot be further miniaturized due to structural limitations
Solution Approach 1:
The semiconductor layer is divided into multiple regions with different polarities (first polarity region and second polarity region) separated by a hole. This segmentation allows the avalanche region to be formed without direct contact between P-type and N-type layers, enabling pixel miniaturization while maintaining signal multiplication capability through the alternating polarity structure.
Solution Approach 2:
The invention transitions from a conventional planar contact structure to a stacked structure with alternating polarities separated by holes. This dimensional reorganization allows the formation of multiple avalanche regions in a compact vertical arrangement, achieving pixel miniaturization while preserving the electron avalanche effect for signal multiplication.
2Reliability
If the P-type semiconductor layer and N-type semiconductor layer are in contact with each other to form an avalanche region, then the image sensor can achieve signal multiplication through electron avalanche effect, but the light-receiving sensitivity is limited in miniaturized pixels
Solution Approach 1:
The semiconductor layer is divided into multiple regions with different polarities (first polarity region and second polarity region) separated by a hole. This segmentation allows the avalanche region to be formed without direct contact between P-type and N-type layers, enabling pixel miniaturization while maintaining signal multiplication capability through the alternating polarity structure.
Solution Approach 2:
The invention creates localized electric field enhancement at the hole edges where the first and second polarity regions are positioned. This local quality optimization concentrates the electric field intensity in specific regions, improving light-receiving sensitivity by enhancing the electron avalanche effect at critical locations while maintaining overall pixel miniaturization.
3Device complexity
If a conventional contact structure is used between P-type and N-type semiconductor layers, then the device structure is simple, but further miniaturization and sensitivity improvement are limited
Solution Approach 1:
The semiconductor layer is divided into multiple regions with different polarities (first polarity region and second polarity region) separated by a hole. This segmentation allows the avalanche region to be formed without direct contact between P-type and N-type layers, enabling pixel miniaturization while maintaining signal multiplication capability through the alternating polarity structure.
Solution Approach 2:
The invention embeds the hole structure within the semiconductor layer, creating a nested configuration where the first and second polarity regions are positioned around the hole. This nesting approach achieves compact pixel structure with enhanced functionality, allowing miniaturization while maintaining relatively simple fabrication processes.
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 light-receiving sensitivity by suppressing potential barriers and optimizing electric field intensity, enabling more efficient electron multiplication and improved performance in miniaturized pixel structures.
Implementation Method 1
an electronic element that outputs one large electric pulse signal by a multiplication effect due to an electron avalanche when one light particle (hereinafter, photon) is incident on the pixel
Implementation Method 2
an avalanche photodiode including an avalanche region
Implementation Method 3
electrons generated by photoelectric conversion
Data Source
AI summary
The present disclosure relates to a solid-state imaging element, an imaging device, and an electronic device capable of improving light-receiving sensitivity. An avalanche region is formed by forming a P+ type semiconductor region connected to an anode into an annular structure having a hole at a center portion at a pixel center as seen in an incident direction of incident light, and forming an N+ type semiconductor region connected to a cathode at a subsequent stage as seen in the incident direction of the hole. This may be applied to an avalanche photodiode.