CMOS Image Sensor Pixel Structure with Deep Groove Light Reflection Shielding
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Solution Overview
Problem
Conventional CMOS image sensors face issues with optical crosstalk between adjacent pixels due to low light transmission through semiconductor materials, leading to reduced pixel resolution and sensitivity, especially as pixel size shrinks.
Innovation Solution
A CMOS image sensor pixel structure featuring a deep groove with a light-transmitting space surrounded by a continuous light reflection shielding layer, primarily made of metal materials, which reflects incident light back onto the photosensitive element, reducing crosstalk and enhancing light absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pixel size is reduced to increase integration, then the number of pixels increases, but the space between adjacent pixels decreases causing increased optical crosstalk
Solution Approach 1:
The patent divides the pixel structure into distinct regions by introducing deep grooves that physically separate adjacent pixels. These grooves create isolated light-receiving regions, preventing light from one pixel from interfering with adjacent pixels, thereby solving the optical crosstalk problem while maintaining high pixel density
Solution Approach 2:
The patent introduces a light-blocking layer as an intermediary substance filled into the deep grooves between pixels. This light-blocking material acts as a mediator that absorbs or blocks stray light, preventing it from reaching adjacent pixels and eliminating optical crosstalk without reducing the number of pixels
2Illumination intensity
If dielectric layers are removed and light-transmitting material is filled to increase light absorption, then light transmission improves, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies different material properties to different regions: the deep grooves between pixels are filled with light-blocking material to prevent crosstalk, while the pixel active regions maintain their light-transmitting characteristics. This localized differentiation achieves both light absorption enhancement and crosstalk reduction without requiring complete removal of dielectric layers
Solution Approach 2:
The patent introduces a vertical dimension by creating deep grooves that extend downward into the substrate. This vertical separation allows light-blocking material to be positioned strategically in the depth direction, preventing lateral light propagation between pixels while maintaining a relatively simple planar manufacturing process
3Reliability
If a light reflection shielding layer is added to reduce optical crosstalk, then pixel resolution and sensitivity improve, but device complexity increases
Solution Approach 1:
The patent combines the light reflection shielding function with the existing deep groove structure. The light-blocking layer is integrated into the grooves that are already necessary for pixel separation, merging the anti-crosstalk function with the structural separation function, thereby reducing overall device complexity while maintaining improved pixel resolution and sensitivity
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 optical crosstalk and improves pixel resolution and sensitivity by ensuring all incident light is absorbed by the photosensitive element, thereby enhancing the overall performance and reliability of the CMOS image sensor.
Implementation Method 1
the side wall of the deep groove is surrounded by a light reflection shielding layer continuously arranged in a longitudinal direction to reflect the light incident on the light reflection shielding layer
Data Source
AI summary
A pixel structure of a CMOS image sensor pixel structure and a manufacturing method thereof. The structure comprises a photosensitive element (37) and a multi-layer structure of a standard CMOS device arranged on the silicon substrate (31). A deep groove (38) having a light-transmitting space therein is formed above the photosensitive element, a side wall of the deep groove is surrounded by a light reflection shielding layer (39) continuously arranged in a longitudinal direction to reflect the light incident on the light reflection shielding layer. The side wall of the deep groove is surrounded by metal interconnects, vias, contact holes and polysilicon in annular configurations, thus the incident light on the deep grove is substantially completely reflected, which avoids the optical crosstalk and effectively improves the optical resolution and sensitivity of the pixel and the performance and reliability of the chip.