Image Sensor Light Retention Structure for NIR Photon Absorption
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Solution Overview
Problem
Existing image sensors, particularly those used in near-infrared (NIR) applications, face challenges in light detection due to reduced photon absorption in the NIR wavelength band, leading to low light sensitivity and poor image quality.
Innovation Solution
The implementation of a pixel structure that includes a plurality of light diffusors and a light-focusing structure with multiple focusing portions, each optically coupled with a corresponding light diffusor, to enhance photon absorption within the photosensitive region while minimizing light escape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional photosensitive region is used for NIR imaging, then the device structure remains simple, but photon absorption is reduced leading to low light sensitivity
Solution Approach 1:
The pixel structure is segmented into multiple functional layers: a photosensitive region, a light-focusing structure with multiple focusing portions, and a light diffusor structure with multiple diffusor portions. This segmentation allows each layer to perform its specific function optimally, with the light-focusing structure concentrating photons onto the photosensitive region and the light diffusor structure redirecting escaped photons back for additional absorption opportunities
Solution Approach 2:
The patent implements a nested structure where the light-focusing structure is positioned above the photosensitive region, and the light diffusor structure is positioned above the light-focusing structure. This nested arrangement allows light to pass through multiple functional layers in sequence, with each layer contributing to photon retention and absorption enhancement without requiring lateral expansion of the device
2Reliability
If the light-focusing structure is made thicker to improve photon retention, then more photons are absorbed, but fabrication difficulty increases
Solution Approach 1:
Instead of increasing the lateral dimensions or thickness of the light-focusing structure to improve photon retention, the patent utilizes the vertical dimension by implementing a multi-layer stacked architecture. The light-focusing structure and light diffusor structure are arranged in vertical layers above the photosensitive region, allowing photon manipulation through vertical stacking rather than lateral expansion. This approach maintains compact device footprint while achieving enhanced photon retention through multiple optical interaction layers
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 the overall optical path in the photosensitive region, improving quantum efficiency and image quality by redirecting and absorbing more photons, and reduces the thickness of the light-focusing structure, facilitating easier IC device fabrication.
Implementation Method 1
a light-focusing structure overlying the plurality of light diffusors. The light-focusing structure includes a plurality of light-focusing portions. Each of the plurality of light-focusing portions overlies, and is configured to focus light on, a corresponding one or more of the plurality of light diffusors
Implementation Method 2
a plurality of light diffusors overlying the photodetector on a second side of the semiconductor layer opposite the first side
Data Source
AI summary
Some embodiments relate to an integrated circuit device including a semiconductor layer, a pixel including a photodetector in the semiconductor layer, a conductive structure electrically coupled to the pixel on a first side of the semiconductor layer, a plurality of light diffusors overlying the photodetector on a second side of the semiconductor layer opposite the first side, and a light-focusing structure overlying the plurality of light diffusors. The light-focusing structure includes a plurality of light-focusing portions. Each of the plurality of light-focusing portions overlies, and is configured to focus light on, a corresponding one or more of the plurality of light diffusors.