Dielectric Layer Isolation for Image Sensor Pixel Crosstalk
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Solution Overview
Problem
Conventional photo diode architectures suffer from significant cross-talk issues due to light interference from tilt angles, affecting the accuracy of color sensing in image sensors used in digital cameras and other image technology products.
Innovation Solution
The implementation of a photo diode structure that includes a photo conversion layer, a color filter layer, and a dielectric layer with a refractive index lower than the photo conversion layer, where the dielectric layer separates the pixels and causes total internal reflection, preventing light from passing between adjacent pixels and reducing cross-talk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional photo diode architecture is used, then manufacturing is simple, but cross-talk between adjacent pixels occurs due to light interference from tilt angles
Solution Approach 1:
A dielectric layer with refractive index n1 is introduced as an intermediary between adjacent photo diodes. This dielectric layer has a lower refractive index than the surrounding semiconductor materials, creating optical barriers that prevent light from one pixel from interfering with adjacent pixels. The dielectric layer acts as a mediator that blocks harmful light propagation while allowing the photo diode structure to function normally.
Solution Approach 2:
The refractive index parameter of the materials surrounding the photo diode is changed by introducing a dielectric layer with specifically controlled refractive index n1. This parameter change creates total internal reflection at the interfaces, preventing light from escaping one pixel and entering adjacent pixels. The refractive index is carefully selected to be lower than both the semiconductor substrate and the overlying layers to achieve optimal light isolation.
2Measurement precision
If dielectric layer with lower refractive index is added to reduce cross-talk, then color sensing accuracy improves, but manufacturing complexity increases
Solution Approach 1:
The dielectric layer serves multiple functions simultaneously: it acts as a refractive index barrier to prevent light cross-talk, provides electrical isolation between adjacent pixels, and can serve as part of the passivation structure. By combining multiple functions into a single layer, the manufacturing process complexity is minimized while achieving effective light isolation and color sensing accuracy.
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 effectively reduces light crosstalk between pixels, enhancing the accuracy of color sensing and improving the overall performance of image sensors by ensuring that each pixel receives and processes light independently.
Implementation Method 1
a dielectric layer that is between the portions of the photo conversion layer and that has a refractive index lower than a refractive index of the photo conversion layer
Data Source
AI summary
A photo diode includes a pixel unit, a photo conversion layer, and a dielectric layer. The pixel unit includes a pair of pixels. The photo conversion layer is above the pixel unit and has a pair of portions, each of which corresponds to a respective one of the pixels. The dielectric layer is between the portions of the photo conversion layer. A method of manufacturing the photo diode is also disclosed.