Back Side Illuminated Near Infrared Image Sensor Optical Confinement
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Solution Overview
Problem
Conventional back side illuminated image sensors face a trade-off between visible light performance and near infrared sensitivity due to the thinning of semiconductor material, which degrades near infrared performance despite the need for thicker material to absorb more infrared light.
Innovation Solution
The integration of deep trench isolation (DTI) structures, total internal reflection, and a scattering structure with an antireflective coating on the semiconductor material to confine near infrared light within the sensor, enhancing sensitivity and reducing optical crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the semiconductor material is thinned to improve visible light performance, then manufacturing precision is improved, but optical crosstalk increases
Solution Approach 1:
The patent employs segmentation through deep trench isolation structures that physically separate adjacent pixels. These trenches, etched into the semiconductor substrate, create optical barriers that prevent light from one pixel from leaking into neighboring pixels, thereby reducing optical crosstalk while maintaining the thinned structure benefits for visible light detection.
Solution Approach 2:
The patent introduces intermediary structures (trenches filled with isolation material) between adjacent pixels. These intermediary elements act as optical barriers that block stray light paths, preventing crosstalk between neighboring photodetectors while allowing the overall sensor to maintain its thinned configuration for optimal visible light response.
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 improves near infrared sensitivity and reduces optical crosstalk by ensuring that near infrared light is absorbed within the sensor, maintaining high image quality across the visible and near infrared spectrum.
Implementation Method 1
a scattering structure proximate to a front side of the semiconductor material such that near infrared light that is reflected from the front side of the semiconductor material is scattered by the scattering structure
Implementation Method 2
The near infrared light that is reflected at the front side of the semiconductor and scattered back through the photodiode in the optical path is totally internally reflected by the deep trench isolation structure
Implementation Method 3
a photodiode disposed proximate to a front side of a semiconductor material to accumulate image charge in response to near infrared light directed into the semiconductor material through a back side of the semiconductor material
Data Source
AI summary
An image sensor includes a photodiode disposed in semiconductor material to accumulate image charge in response to light directed through a back side of the semiconductor material. A scattering structure is disposed proximate to the front side of the semiconductor material such that the light that is directed into the semiconductor material through the back side is scattered back through the photodiode. A deep trench isolation structure is disposed in the semiconductor material that isolates the photodiode and defines an optical path such that the light that is scattered back through the photodiode in the optical path is totally internally reflected by the DTI. An antireflective coating is disposed on the back side of the semiconductor material and totally internally reflects the light scattered by the scattering structure to confine the light to remain in the optical path until it is absorbed.