Dielectric Stack Reflective Element for Near-IR Quantum Efficiency
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Solution Overview
Problem
Current image sensor devices face challenges in achieving improved performance and reliability, particularly in sensing invisible light such as near-infrared wavelengths, where quantum efficiency is low due to limited absorption and reflection capabilities.
Innovation Solution
The implementation of a light-sensing device with a light-reflective element comprising a stack of multiple pairs of dielectric layers with varying refractive indices, positioned between the light-sensing region and the light-receiving surface, enhances reflection and absorption of specific wavelength ranges like red light and near-IR light, thereby improving quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional image sensor device is used, then the device structure is simple, but the quantum efficiency for longer wavelength lights (near-IR) is low
Solution Approach 1:
The patent applies composite materials by implementing a light-reflective element composed of multiple dielectric layers with different refractive indices (e.g., silicon oxide, silicon nitride, silicon oxynitride) stacked in specific sequences. This composite structure enables enhanced reflection of longer wavelength light through constructive interference, thereby improving quantum efficiency without requiring a complete redesign of the sensor architecture.
Solution Approach 2:
The patent addresses the limitation in light absorption by adding a new dimensional aspect to the optical path through the light-reflective element. By introducing multiple reflective interfaces at different depths (vertical dimension), the light is reflected multiple times through the photodetector region, increasing the interaction path length and probability of absorption for longer wavelengths that would otherwise pass through without being detected.
2Reliability
If the quantum efficiency for near-IR light is improved using a light-reflective element, then the performance in low-light conditions is enhanced, but the manufacturing process becomes more complex
Solution Approach 1:
The light-reflective element is segmented into multiple discrete dielectric layers, each with specific thickness and refractive index properties. This segmentation allows for optimized optical performance through interference effects while enabling modular manufacturing approaches where layers can be deposited sequentially using standard semiconductor fabrication techniques, balancing performance improvement with manufacturing feasibility.
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 significantly enhances the quantum efficiency for longer wavelength lights, improving the overall performance and reliability of the image sensor device, especially in low-light conditions.
Implementation Method 1
a light-reflective element over the semiconductor substrate. The light-sensing region is between the light-reflective element and a light-receiving surface of the semiconductor substrate
Implementation Method 2
enhances reflection and absorption of specific wavelength ranges like red light and near-IR light, thereby improving quantum efficiency
Data Source
AI summary
A method for forming a light-sensing device is provided. The method includes forming a light-sensing region in a semiconductor substrate. The semiconductor substrate has a front surface and a light-receiving surface opposite to the front surface. The method also includes forming a first dielectric layer over the front surface and forming a second dielectric layer over the first dielectric layer. The second dielectric layer has a different refractive index than that of the first dielectric layer, and the first dielectric layer and the second dielectric layer together form a (or a part of a) light-reflective element. The method further includes partially removing the first dielectric layer and the second dielectric layer to form a contact opening. In addition, the method includes forming a conductive contact to partially (or completely) fill the contact opening.