Image Sensor Pixel With Deep Insulated Trench For Cross-Talk Suppression
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Solution Overview
Problem
Current image sensor pixels experience cross-talk due to electron transmission from one pixel to adjacent pixels, leading to incorrect reproduction of the original image signal during electrical signal conversion.
Innovation Solution
A pixel structure is developed with a substrate surrounded by a trench filled with an insulator, featuring a photodiode with joined P-type and N-type diffusion areas and a pass transistor, where the trench penetrates the substrate from the upper to the lower portion and is filled with an insulator, completely isolating the pixel from adjacent pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the area of the photodiode is increased to improve image signal reception, then the fill factor is improved, but the area of the pixel must be increased which conflicts with the trend of decreasing pixel area for higher resolution
Solution Approach 1:
The patent introduces a vertical dimension by forming a deep trench structure that penetrates through the substrate thickness. This vertical isolation structure allows the photodiode area to be maximized in the horizontal plane without increasing the overall pixel footprint, as the isolation is achieved through the third dimension (depth) rather than horizontal expansion.
Solution Approach 2:
The pixel structure is segmented into distinct regions separated by the deep trench. The trench divides the substrate into isolated pixel regions, allowing each pixel's photodiode to occupy maximum area within its confined region while preventing interference with adjacent pixels. This segmentation enables independent optimization of each pixel's light-receiving area.
2Ease of manufacture
If a shallow trench insulator structure is used to isolate pixels, then manufacturing is simplified, but cross-talk between adjacent pixels occurs due to insufficient isolation depth
Solution Approach 1:
The patent changes the critical parameter of trench depth from shallow to deep (penetrating through the substrate). This parameter change fundamentally improves the isolation effectiveness and cross-talk suppression while maintaining compatibility with standard semiconductor manufacturing processes. The deep trench structure provides sufficient electrical isolation between pixels without requiring complex manufacturing steps.
3Area of stationary object
If the number of MOS transistors in each pixel is reduced to decrease pixel area, then the photodiode area can be increased, but the functionality and reliability of pixel operations may be compromised
Solution Approach 1:
The patent merges the photodiode and pass transistor into a single integrated structure where the pass transistor is formed within the same semiconductor region as the photodiode. This merging reduces the total component count and eliminates the need for separate transistor structures, thereby decreasing pixel area while maintaining full operational functionality through the integrated design.
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 design effectively suppresses cross-talk by blocking the path for charge transmission between pixels, ensuring accurate image signal reproduction.
Implementation Method 1
the pixel for picking up an image signal is surrounded by a trench which penetrates the substrate from the upper portion to the lower portion of the substrate, and the trench is filled with an insulator
Implementation Method 2
Each of the pixels includes a photodiode that directly receives the image signal. The photodiode PD generates a charge corresponding to the incident image signal.
Data Source
AI summary
Provided is a pixel for picking up an image signal capable of suppressing an occurrence of a cross-talk. The pixel for picking up an image signal includes a substrate surrounded by a trench, a photodiode, and a pass transistor. The photodiode is formed at an upper portion of the substrate and includes a P-type diffusion area and an N-type diffusion area which are joined with each other in a longitudinal direction. The pass transistor is formed at the upper portion of the substrate and includes the one terminal that is the joined P-type diffusion area and the N-type diffusion area, the other terminal that is a floating diffusion area, and a gate terminal disposed between the two terminals. The pixel for picking up an image signal is surrounded by the trench which penetrates the substrate from the upper portion to the lower portion of the substrate, and the trench is filled with an insulator.