Photodetector Wiring Structure With Light Shielding for Pixel Crosstalk
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Solution Overview
Problem
Avalanche photodiode (APD) pixels in arrays experience light leakage through wiring layers, leading to crosstalk and erroneous measurements.
Innovation Solution
A photodetector design incorporating a light shielding wall that divides the interlayer insulating films between adjacent photoelectric conversion sections, preventing light from one pixel from reaching adjacent pixels and reducing crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a wiring layer is provided to connect photoelectric conversion sections in an array, then electrical connectivity and signal readout are improved, but light leakage occurs through the wiring layer causing crosstalk between adjacent pixels
Solution Approach 1:
A light shielding wall is introduced as an intermediary element between adjacent photoelectric conversion sections. This wall is formed within the wiring layer structure and serves to block light from leaking between pixels while maintaining the electrical connectivity function of the wiring layer. The light shielding wall acts as a mediator that resolves the conflict between needing continuous wiring for electrical connection and preventing light transmission to avoid crosstalk.
2Object-generated harmful factors
If the wiring layer is made more opaque to block light, then crosstalk is reduced, but electrical conductivity and signal transmission may be compromised
Solution Approach 1:
The wiring layer is segmented into multiple parts: conductive wiring portions for electrical connection and light shielding wall portions for optical isolation. This segmentation allows different regions of the same layer to perform different functions - some areas maintain high electrical conductivity while other areas provide light blocking. The wiring layer is thus divided into functionally distinct segments that collectively solve both the connectivity and crosstalk problems.
3Measurement precision
If a light shielding wall is added to prevent crosstalk, then measurement precision is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The light shielding wall is merged with the existing wiring layer structure rather than being added as a completely separate component. The light shielding wall utilizes the same formation process and structural framework as the wiring layer, combining the electrical connection function and optical shielding function into a single integrated structure. This merging approach reduces overall device complexity compared to adding independent shielding structures.
Solution Approach 2:
The wiring layer is designed to serve multiple functions simultaneously: electrical connectivity, signal transmission, and optical shielding. By making the wiring layer multi-functional, the need for separate dedicated shielding structures is eliminated. The same layer that provides electrical connection also provides light blocking, reducing the total number of components and simplifying the overall device architecture.
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
The light shielding wall effectively suppresses crosstalk between adjacent pixels, enhancing measurement accuracy by preventing light leakage and improving the reliability of photodetector performance.
Implementation Method 1
a light shielding wall that divides at least one of at least a part of an interlayer insulating film of the first wiring layer or at least a part of a portion of an interlayer insulating film of the second wiring layer on a side of the first semiconductor substrate into respective portions corresponding to a first photoelectric conversion section and a second photoelectric conversion section
Implementation Method 2
The SPAD is a device capable of detecting one photon for each pixel by multiplying a carrier generated by photoelectric conversion in a PN junction region of a high electric field
Implementation Method 3
The Geiger-mode avalanche photodiode is also called a single photon avalanche diode (SPAD). The SPAD is a device capable of detecting one photon for each pixel by multiplying a carrier generated by photoelectric conversion in a PN junction region of a high electric field
Data Source
AI summary
Crosstalk is suppressed in a wiring layer. A photodetector includes a first semiconductor substrate including a first semiconductor layer in which a plurality of photoelectric conversion sections is provided in an array along a row direction and a column direction, and a first wiring layer provided on a main surface side of the first semiconductor layer, a second semiconductor substrate including a second semiconductor layer provided with an active element and a second wiring layer provided on a main surface side of the second semiconductor layer, the second wiring layer being overlapped with and joined to the first wiring layer, and a light shielding wall that divides at least one of at least a part of an interlayer insulating film of the first wiring layer or at least a part of a portion of an interlayer insulating film of the second wiring layer on a side of the first semiconductor substrate into respective portions corresponding to a first photoelectric conversion section and a second photoelectric conversion section adjacent to each other of the plurality of photoelectric conversion sections.