Image Sensor Antireflection Stack for Blue QE and Low Dark Current
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Solution Overview
Problem
Current image sensors face challenges in achieving sharp images due to issues such as light reflection and leakage currents, which affect image quality and quantum efficiency, particularly in blue light detection.
Innovation Solution
The proposed image sensor incorporates an antireflection structure with a stacked configuration of dielectric layers, including a titanium oxide layer, and grooves on the edge region to reduce reflectivity and prevent leakage currents, while also utilizing a microlens array and color filters to enhance light reception and image clarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional single-layer antireflection coating is used, then the manufacturing process is simple, but light reflection is not sufficiently reduced and quantum efficiency is poor
Solution Approach 1:
The patent applies composite materials by stacking multiple dielectric layers (first dielectric layer, titanium oxide layer, second dielectric layer, and third dielectric layer) with different refractive indices to form an antireflection structure. This multi-layer composite configuration reduces light reflection more effectively than a single-layer coating while maintaining manufacturing feasibility through sequential deposition processes.
Solution Approach 2:
The patent transitions from a single-layer to a multi-layer antireflection structure by adding dimensional complexity in the vertical stacking direction. This dimensional change allows for better control of optical properties across different wavelengths and angles, improving light-receiving efficiency without significantly complicating the manufacturing process.
2Object-affected harmful factors
If the antireflection structure covers the entire substrate including edge regions, then light reflection is reduced across the surface, but leakage currents increase between adjacent pixels
Solution Approach 1:
The patent applies local quality by making the third dielectric layer penetrate through the second dielectric layer and titanium oxide layer to contact the first dielectric layer specifically in the edge region, while maintaining the full stacked structure in the pixel array region. This localized modification reduces leakage currents at pixel boundaries while preserving the antireflection performance in active pixel areas.
Solution Approach 2:
The patent segments the antireflection structure into different configurations for different regions: the pixel array region maintains the complete four-layer stack, while the edge region has the third dielectric layer extending downward to contact the first dielectric layer. This segmentation allows independent optimization of each region to address both reflection and leakage current issues.
3Reliability
If blue light detection is enhanced, then quantum efficiency for blue pixels improves, but dark current and white spots increase affecting image quality
Solution Approach 1:
The patent uses composite materials with the titanium oxide layer having high refractive index and appropriate thickness to enhance blue light absorption and quantum efficiency. The combination of multiple dielectric layers with different optical properties allows selective enhancement of blue light detection while the structured configuration helps suppress dark current and white spot formation.
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 increases light-receiving efficiency, reduces dark current and white spots, and improves quantum efficiency, particularly for blue color pixels, resulting in sharper image quality and reduced operation errors.
Implementation Method 1
an antireflection structure on the second surface... The antireflection structure may include a first dielectric layer, a titanium oxide layer, a second dielectric layer, and a third dielectric layer that are sequentially stacked
Implementation Method 2
a microlens array on the antireflection structure
Implementation Method 3
Each of the pixels includes a photodiode (PD). The photodiode serves to transform an incident light into an electrical signal
Data Source
AI summary
Disclosed is an image sensor including a first substrate that has a first surface and a second surface opposite to the first substrate and including a pixel array region and an edge region, an antireflection structure on the second surface, a pixel separation part in the first substrate and separating pixels from each other, and a microlens array on the antireflection structure. The antireflection structure includes a first dielectric layer, a titanium oxide layer, a second dielectric layer, and a third dielectric layer that are sequentially stacked. The first dielectric layer, the second dielectric layer, and the third dielectric layer include different materials from each other. On the edge region, the third dielectric layer penetrates the second dielectric layer and the titanium oxide layer to contact with the first dielectric layer.