Back-Side Illuminated Image Sensor Internal Reflection Enhancement
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Solution Overview
Problem
Back-side illuminated (BSI) image sensors face reduced quantum efficiency due to low absorption of near-infrared (NIR) radiation, as forward-traveling NIR light reflects back and escapes, rather than being absorbed by the sensor.
Innovation Solution
An image sensor integrated chip with an internal reflection enhancement structure, featuring protrusions, recesses, and absorption enhancement layers on the substrate, designed to increase internal reflection of NIR radiation, thereby reducing backscattered light and enhancing quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If back-side illuminated (BSI) image sensors are used, then low power consumption and small size are achieved, but quantum efficiency is reduced due to low absorption of near-infrared (NIR) radiation
Solution Approach 1:
The patent converts the harmful backscattered NIR light that would normally escape into a beneficial resource by introducing an internal reflection enhancement structure. This structure reflects the escaped NIR light back into the sensor substrate, allowing it to be absorbed and utilized by the imaging element, thereby converting energy loss into useful signal detection and improving quantum efficiency
Solution Approach 2:
The patent adds a new dimensional element to the BSI sensor structure by introducing an internal reflection enhancement structure with specific geometric features (protrusions and recesses). This three-dimensional structure creates additional light paths and reflection surfaces within the substrate, enabling NIR light that would have escaped in straight lines to be redirected and absorbed, thus adding a spatial dimension to light management
2Device complexity
If forward-traveling NIR light is allowed to pass through the sensor, then device simplicity is maintained, but backscattered light escapes reducing performance
Solution Approach 1:
The patent introduces an intermediary component - the internal reflection enhancement structure - that mediates between the incoming NIR light and the imaging element. This structure acts as an intermediate layer that first receives the forward-traveling light, reflects it back, and then allows the reflected light to be absorbed by the imaging element, thereby maintaining device simplicity while improving performance
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 internal reflection enhancement structure effectively increases the absorption of NIR radiation within the sensor, improving quantum efficiency and performance by reflecting and re-absorbing NIR light, thus reducing the amount of backscattered radiation.
Implementation Method 1
An internal reflection enhancement structure arranged along a first side of the substrate. The internal reflection enhancement structure is configured to reflect reflected NIR radiation back into the substrate.
Implementation Method 2
forward-traveling NIR light in the BSI sensors can touch the circuit electronics at the front side of the BSI sensors. The NIR light can then reflect backward through the substrate.
Data Source
AI summary
The present disclosure, in some embodiments, relates to an integrated chip. The integrated chip has an image sensor within a substrate. A first dielectric has an upper surface that extends over a first side of the substrate and over one or more trenches within the first side of the substrate. The one or more trenches laterally surround the image sensor. An internal reflection structure arranged over the upper surface of the first dielectric. The internal reflection structure is configured to reflect radiation exiting from the substrate back into the substrate.