Avalanche Photodetector Pixel Isolation for Crosstalk Control
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Solution Overview
Problem
Crosstalk occurs in photodetectors due to leakage of internal luminescence between adjacent pixels during avalanche multiplication, which affects the accuracy and performance of distance measurement.
Innovation Solution
The photodetector incorporates a pixel separation section and connection wiring that electrically isolates each pixel, reducing light leakage by providing independent connection paths for each pixel through vias and multilayer wiring layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If avalanche multiplication is performed in photodetectors, then signal amplification is achieved, but crosstalk occurs due to leakage of internal luminescence between adjacent pixels
Solution Approach 1:
The semiconductor substrate is divided into independently controllable regions using pixel separation sections that extend from the first surface to the second surface. These separation sections create independent electrical pathways for each pixel, preventing luminescence leakage between adjacent pixels during avalanche multiplication while maintaining signal amplification capability.
Solution Approach 2:
Pixel separation sections act as intermediary structures between adjacent pixels. These sections include insulating layers and conductive layers that mediate the electrical isolation, allowing each pixel to maintain its own electrical field and preventing harmful luminescence crosstalk while preserving the avalanche multiplication function.
2Reliability
If pixel separation sections extend from first surface to second surface, then electrical isolation between adjacent pixels is improved, but device complexity increases
Solution Approach 1:
The pixel separation sections are nested within the existing semiconductor substrate structure. The insulating layers and conductive layers are integrated into the substrate during fabrication, with the separation sections positioned between adjacent pixels. This nesting approach achieves effective electrical isolation without adding external complex structures.
Solution Approach 2:
The pixel separation sections utilize changes in electrical parameters (conductivity, insulation) achieved through controlled doping and layer deposition. By adjusting the electrical properties of the separation sections, effective isolation is achieved while maintaining compatibility with existing fabrication processes, thus avoiding excessive complexity.
3Object-affected harmful factors
If connection wiring is provided independently for each pixel, then light leakage from adjacent pixels is reduced, but manufacturing complexity increases
Solution Approach 1:
Multiple connection wirings for different pixels are merged into a single multilayer wiring layer structure. The connection wirings are integrated with the pixel separation sections and contact layers, allowing simultaneous electrical connection and isolation functions. This merging reduces the number of separate manufacturing steps while maintaining independent connection paths for each pixel.
Solution Approach 2:
The multilayer wiring layer serves multiple functions: it provides connection pathways for signal extraction, maintains electrical isolation between pixels, and integrates with the pixel separation sections. This multi-functionality reduces manufacturing complexity by consolidating multiple requirements into a single structural element that can be fabricated using standard 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 design effectively suppresses crosstalk between adjacent pixels, enhancing the accuracy and performance of distance measurement by minimizing light interference.
Implementation Method 1
a light-receiving section provided inside the semiconductor substrate for each of the pixels and generating carriers corresponding to a received light amount by photoelectric conversion
Implementation Method 2
the multiplication section performing avalanche multiplication of the carriers generated in the light-receiving section
Data Source
AI summary
A photodetector of an embodiment of the disclosure includes: a semiconductor substrate having opposed first and second surfaces and including a pixel array section including pixels in array in an in-plane direction; a light-receiving section provided inside the substrate for each pixel and generating carriers corresponding to a received light amount by photoelectric conversion; a multiplication section performing avalanche multiplication of the carriers generated in the light-receiving section and including, for each pixel, first and second electrically-conductive regions having different electrically-conductive types and stacked on the first surface side; a pixel separation section provided between the adjacent pixels to extend from the first surface to the second surface, and electrically separating the adjacent pixels; a first contact layer provided around each pixel along the pixel separation section on the first surface and electrically coupled to the light-receiving section; a second contact layer provided on the first surface and electrically coupled to the multiplication section; and connection wiring provided independently for each pixel and electrically coupling the first contact layer and one or more wiring layers provided on the first surface side and included in a multilayer wiring layer.