Recessed Light Sensor Electrode Structure for Lower Reflection
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Solution Overview
Problem
Light detection sensors face issues of light loss and dark current due to reflection, absorption, and substrate damage during manufacturing, which affect photoelectric conversion efficiency.
Innovation Solution
A light detection sensor design featuring a substrate with a deep trench isolator, recesses, a transparent electrode, and insulating films to minimize light reflection and dark current, enhancing photoelectric conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional photodiode structure is used, then the device is simple to manufacture, but light is lost due to reflection and absorption at the substrate surface
Solution Approach 1:
The substrate surface is segmented into multiple regions including a light incident surface, a first surface with a first transparent electrode, and a second surface with a second transparent electrode. This segmentation allows light to be incident from multiple directions and reduces reflection loss by distributing the light reception across different surfaces and angles.
Solution Approach 2:
The patent transitions from a conventional single-sided light incident structure to a multi-sided structure where light can be incident from both the light incident surface and the first surface. This dimensional change enables light reception from multiple angles and reduces reflection loss by providing alternative light paths.
2Loss of energy
If the substrate is heavily processed during manufacturing, then the photoelectric conversion efficiency can be improved, but the substrate may be damaged causing dark current
Solution Approach 1:
A passivation layer is formed on the substrate surface before subsequent processing steps. This passivation layer acts as a protective cushion that prevents substrate damage during manufacturing processes, reducing the generation of dark current while still allowing for necessary processing to improve photoelectric conversion efficiency.
Solution Approach 2:
The passivation layer serves as an intermediary between the substrate and the manufacturing processes. It protects the substrate from direct damage while allowing the processing to continue, thus maintaining substrate integrity and reducing dark current generation.
3Illumination intensity
If transparent electrodes are added to reduce reflection, then light receptivity is improved, but the device complexity increases
Solution Approach 1:
The first transparent electrode and second transparent electrode serve multiple functions: they act as electrical contacts for the photodiode and simultaneously function as anti-reflection coatings to reduce light reflection. This multi-functionality improves light receptivity without proportionally increasing device complexity.
Solution Approach 2:
The transparent electrodes are designed with optical properties that reduce reflection across the visible spectrum. By optimizing the refractive index and thickness of these electrodes, the structure minimizes reflection loss and maximizes light absorption by the photodiode.
4Reliability
If deep trench isolators are used to define pixel areas, then pixel isolation is improved, but manufacturing complexity increases
Solution Approach 1:
The substrate is divided into discrete pixel areas by deep trench isolators that extend through the substrate thickness. This segmentation provides effective electrical and optical isolation between adjacent pixels, preventing cross-talk and improving image quality.
Solution Approach 2:
The deep trench isolators are formed early in the manufacturing process, before subsequent processing steps. This preliminary action establishes the pixel boundaries and isolation structures that will guide subsequent fabrication steps, simplifying the overall manufacturing sequence.
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 design improves light receptivity and reduces dark current, leading to enhanced photoelectric conversion efficiency and reduced substrate defects.
Implementation Method 1
a first insulating film between the transparent electrode and the second surface and between the transparent electrode and the inner surface of the at least one recess
Implementation Method 2
at least one recess into the pixel area from the second surface; a transparent electrode on the second surface and an inner surface of the at least one recess
Implementation Method 3
a light detection sensor may include a photodiode (PD) as a photoelectric conversion element... When the light is incident on the photodiode, part of the light may be lost due to reflection and/or absorption
Data Source
AI summary
Provided is a light detection sensor including: a substrate including a first surface and a second surface opposite to the first surface, wherein the second surface is a light incident surface; a deep trench isolator within a deep trench in the substrate and defining a pixel area; at least one recess into the pixel area from the second surface; a transparent electrode on the second surface and an inner surface of the at least one recess; and a first insulating film between the transparent electrode and the second surface and between the transparent electrode and the inner surface of the at least one recess.