Back Side Illuminated Image Sensor Pixel Isolation
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Solution Overview
Problem
Current image sensors face challenges in maximizing quantum efficiency and minimizing optical crosstalk, which affects their performance by allowing photons to be absorbed by adjacent pixels, thereby reducing precision and efficiency.
Innovation Solution
A back side illuminated (BSI) image sensor manufacturing method involving a semiconductive substrate with a recess, a conductive column, and dielectric layers is employed to isolate pixels and prevent cross-talk, using a conductive column to separate light within individual pixels and a second dielectric layer to reflect light back into the intended pixel, enhancing quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional image sensor structure is used, then manufacturing is simpler, but optical crosstalk occurs between adjacent pixels reducing precision
Solution Approach 1:
The device divides the sensor into isolated pixel units using deep trenches and conductive columns. Each pixel is segmented from its neighbors by these structural elements, preventing optical crosstalk while maintaining individual pixel functionality. The segmentation creates physical barriers that confine light to intended detection areas.
Solution Approach 2:
The patent applies different structural characteristics to different regions: deep trenches with conductive filling at pixel boundaries for isolation, specific dielectric materials for light reflection, and tailored pixel depth variations. These localized structural modifications optimize light confinement and reflection properties at critical interfaces without affecting the entire device uniformly.
2Reliability
If light is allowed to travel freely through the sensor, then quantum efficiency might be improved, but optical crosstalk increases as photons are absorbed by adjacent pixels
Solution Approach 1:
The patent introduces intermediary structures between pixels including deep trenches filled with conductive material and dielectric layers with specific refractive indices. These intermediaries act as barriers and light-manipulating elements that prevent direct optical interaction between adjacent pixels while allowing each pixel to efficiently capture its designated light.
Solution Approach 2:
The patent converts potentially harmful optical crosstalk into beneficial light reflection by using dielectric layers with carefully selected refractive indices. These layers reflect stray light back into the intended pixel rather than allowing it to reach adjacent pixels, transforming what would be interference into a useful light-recapture mechanism that enhances quantum efficiency.
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 method effectively reduces optical crosstalk and enhances quantum efficiency by ensuring light is captured within the intended pixel, thereby improving the precision and performance of the image sensor.
Implementation Method 1
a second dielectric layer covering the conductive column and the first dielectric layer
Data Source
AI summary
Some embodiments of the present disclosure provide a method of manufacturing a back side illuminated (BSI) image sensor. The method includes receiving a semiconductive substrate; forming a photosensitive element at a front side of the semiconductive substrate; forming a transistor coupled to the photosensitive element; forming a recess at a back side of the semiconductive substrate; forming a first dielectric layer lining to a side portion of the recess and over the back side of the semiconductor substrate; covering a conductive material over the first dielectric layer and filling in the recess; forming a conductive column on top of the recess by patterning the conductive material; and forming a second dielectric layer covering the conductive column and the first dielectric layer.