Image Sensor Dielectric Grid for Crosstalk Reduction
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Solution Overview
Problem
Image sensors suffer from optical crosstalk due to incident light overflowing from one pixel grid to neighboring elements, leading to reduced optical sensitivity and poor color separation.
Innovation Solution
The design incorporates a grid structure with a first and second portion, where the second portion has a greater angle than the first, causing incident light to be refracted or reflected back into the same pixel, preventing crosstalk. This is achieved through a manufacturing process involving etching and deposition of dielectric and metal materials, with color filters aligned to the grid to enhance light refraction and reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pixel grid structure is used, then the device complexity is low and manufacturing is easy, but optical crosstalk occurs between neighboring pixels reducing optical sensitivity and color separation
Solution Approach 1:
The grid structure is divided into multiple portions (first portion and second portion) with different angles relative to the substrate. This segmentation allows each portion to perform different optical functions: the first portion allows light transmission while the second portion reflects light back into the pixel, thereby reducing optical crosstalk and improving optical sensitivity without requiring complete structural redesign
Solution Approach 2:
Different portions of the grid are assigned different local properties (angles). The first portion has a first angle that allows light transmission, while the second portion has a second angle that reflects light. This local differentiation enables the grid to simultaneously achieve light transmission and crosstalk reduction functions in different spatial locations
2Manufacturing precision
If the grid structure is modified to reduce crosstalk, then optical sensitivity and color separation improve, but the manufacturing process becomes more complex involving multiple etching and deposition steps
Solution Approach 1:
The grid structure with different angles is formed before depositing the color filters. This preliminary formation of the angular grid structure allows the subsequent color filter deposition to align with the existing grid features, ensuring precise color separation while using standard deposition processes without requiring additional complex alignment steps
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 solution effectively reduces crosstalk, improving optical sensitivity and color separation by ensuring light is focused within its intended pixel, thereby enhancing the overall performance of the image sensor.
Implementation Method 1
causing incident light to be refracted or reflected back into the same pixel
Implementation Method 2
causing incident light to be refracted or reflected back into the same pixel
Data Source
AI summary
An image sensor includes a substrate, a first photosensitive unit, a second photosensitive unit, a buffer layer, a dielectric grid, a first color filter, and a second color filter. The first photosensitive unit and the second photosensitive unit are in the substrate. The buffer layer covers the substrate, the first photosensitive unit and the second photosensitive unit. The dielectric grid is over the buffer layer and between the first photosensitive unit and the second photosensitive unit. The dielectric grid has a round top surface. The first color filter is over the first photosensitive unit. The first color filter is in contact with the round top surface and the buffer layer. The second color filter is over the second photosensitive unit.