SPAD Light Receiving Element Electric Field Relaxation
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Solution Overview
Problem
Existing light receiving elements in direct time-of-flight distance-measurement schemes face challenges in relaxing the electric field between cathode and anode contact regions while preventing the area from expanding, which affects dark-current properties and increases the element's size due to shallow trench isolation.
Innovation Solution
A light receiving element with a single photon avalanche diode (SPAD) integrated in a semiconductor layer, featuring a cathode and anode electrode in a wiring layer for reverse bias voltage application, an insulating buried layer between contact regions, and a surface pinning layer connected to ground potential, along with an N-type diffusion layer covered by the buried layer to manage the electric field and prevent area expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If shallow trench isolation is used to relax the electric field between cathode and anode contact regions, then dark-current properties are improved, but the area of the light receiving element expands
Solution Approach 1:
The patent introduces a buried layer that extends vertically into the semiconductor substrate from the rear surface, creating a three-dimensional electric field relaxation structure. This vertical dimension allows the isolation effect to occur without increasing the planar area of the light receiving element, thereby resolving the contradiction between improving dark-current properties and maintaining compact area.
Solution Approach 2:
The buried layer acts as an intermediary structure between the cathode and anode contact regions. It provides electric field relaxation and isolation functionality without requiring the traditional shallow trench isolation structure that would expand the device area. The buried layer mediates the electric field interaction while maintaining compact geometry.
2Reliability
If the area of the light receiving element is increased to relax the electric field, then dark-state properties are improved, but the element size expands
Solution Approach 1:
The buried layer extends vertically into the substrate, utilizing the depth dimension to achieve electric field relaxation. This allows improvement of dark-state properties without increasing the lateral dimensions of the element, thereby preventing overall volume expansion while maintaining reliable dark-state performance.
3Manufacturing precision
If shallow trench isolation is implemented to manage electric field, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts the electric field management function from the traditional shallow trench isolation structure and implements it through a buried layer. This simplifies the overall device structure by eliminating the need for complex trench isolation formation processes while maintaining precise electric field control through the buried layer configuration.
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 effectively relaxes the electric field between the cathode and anode contact regions, improving dark-state properties and preventing area expansion, thus enhancing the performance of the light receiving element.
Implementation Method 1
an insulating buried layer located between either one of the cathode contact region and the anode contact region, and a surface on an opposite side to a light incident side of the semiconductor layer
Implementation Method 2
a single photon avalanche diode (SPAD) element formed in a semiconductor layer and provided for each of pixels disposed into an array form
Implementation Method 3
single photon avalanche diode (SPAD) element
Data Source
AI summary
An embodiment of the present technology includes an avalanche photodiode including a substrate including a first side with a first surface and a second side with a second surface that is opposite the first surface. The second surface is a light-incident surface of the substrate. The avalanche photodiode includes an anode region disposed in the substrate at the first side of the substrate, an anode electrode coupled to the anode region, a cathode region disposed in the substrate at the first side of the substrate, a cathode electrode coupled to the cathode region, and an insulating layer disposed in the substrate at the first side of the substrate. The anode electrode or the cathode electrode passes through the insulating layer.