Avalanche Photodiode Cell Isolation for Optical Crosstalk Reduction
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Solution Overview
Problem
Existing semiconductor photodetection devices experience significant optical crosstalk due to secondary light generated by avalanche photodiodes, which affects the reliability and sensitivity of the device.
Innovation Solution
Incorporating a light-shielding member with a projecting portion inside the trench and covered by an insulating layer to prevent secondary light from reaching adjacent cells, while using a material that reflects light to enhance sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the light-shielding member includes a projecting portion that extends out from the semiconductor substrate, then optical crosstalk is reduced more reliably, but the light-shielding member is exposed to the atmospheric environment and may corrode
Solution Approach 1:
An insulating layer is introduced as an intermediary between the light-shielding member and the atmospheric environment. This insulating layer covers the projecting portion of the light-shielding member, preventing direct exposure to atmospheric corrosion while maintaining the light-shielding function. The insulating layer acts as a protective mediator that resolves the contradiction between achieving superior optical isolation and ensuring structural durability.
2Object-affected harmful factors
If a low refractive index substance is disposed inside the trench as a light-shielding member, then optical crosstalk is reduced, but the light-shielding member may still be exposed to atmospheric environment and corrode
Solution Approach 1:
The solution employs a composite structure combining the light-shielding member (made of low refractive index substance) with an insulating layer. This composite configuration allows the inner material to provide optimal optical shielding properties while the outer insulating layer provides environmental protection and corrosion resistance, thereby resolving the contradiction between optical performance and durability.
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 configuration effectively reduces optical crosstalk, improves sensitivity by increasing photoelectron generation, and enhances the durability of the light-shielding member by protecting it from atmospheric corrosion.
Implementation Method 1
The low refractive index substance reflects plasma emission generated during carrier multiplication in the avalanche photodiode
Implementation Method 2
a plurality of cells each including an avalanche photodiode arranged to operate in a Geiger mode... makes use of avalanche multiplication
Data Source
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AI summary
A semiconductor substrate has a first main surface and a second main surface that oppose each other and a plurality of cells that are arrayed two-dimensionally in a matrix. Each cell includes at least one avalanche photodiode arranged to operate in a Geiger mode. A trench penetrating through the semiconductor substrate is formed in the semiconductor substrate to surround each cell when viewed in a direction orthogonal to the first main surface. A light-shielding member optically separates mutually adjacent cells of the plurality of cells. The light-shielding member includes a first portion extending in a thickness direction of the semiconductor substrate between an opening end of the trench at the first main surface and an opening end of the trench at the second main surface and a second portion projecting out from the second main surface. The insulating film includes a portion that covers the second portion.