CMOS Image Sensor Pixel Optics for Crosstalk and SNR Control
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Solution Overview
Problem
Image sensor devices with CMOS technology face issues with crosstalk due to dielectric films increasing the number of optical paths, leading to signal-to-noise ratio (SNR) degradation.
Innovation Solution
Incorporating a convex dielectric lens between the color filter and the substrate in each pixel region of the image sensor device, which condenses incident light into a photo-sensitive element, thereby improving quantum efficiency and avoiding crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If dielectric films are used in the image sensor device with CMOS technology, then the device structure is formed, but the number of optical paths increases causing crosstalk and SNR degradation
Solution Approach 1:
The patent extracts and removes the harmful optical paths created by dielectric films by introducing a light blocking structure (grid) that selectively blocks stray light while allowing useful light to pass through to the photodetector, thereby eliminating crosstalk without removing the necessary dielectric films
Solution Approach 2:
The patent introduces a light blocking grid as an intermediary element between the dielectric films and the photodetector. This grid acts as a mediator that selectively blocks harmful optical paths while permitting useful light transmission, resolving the contradiction between maintaining device structure and preventing crosstalk
2Object-affected harmful factors
If a grid is used to block optical paths, then crosstalk is reduced, but incident light may dissipate into other pixels resulting in SNR degradation
Solution Approach 1:
The patent applies local quality by making the light blocking grid selectively transparent in certain regions and opaque in others. The grid structure allows useful light to pass through while blocking stray light at specific locations, creating localized optical path control that prevents crosstalk without sacrificing signal intensity
Solution Approach 2:
The patent employs a convex lens structure with curved surface to focus incident light onto the photodetector. This curvature enables the lens to collect and concentrate light rays that would otherwise diverge or be blocked by the grid, maintaining high SNR while the grid blocks crosstalk
3Manufacturing precision
If micro-lenses are used to condense incident light, then light focusing is improved, but dielectric films still create multiple optical paths causing crosstalk
Solution Approach 1:
The patent merges the light focusing function of the convex lens with the light blocking function of the grid structure. These two elements work together synergistically - the lens concentrates useful light while the grid simultaneously blocks stray optical paths, achieving both improved focusing and eliminated crosstalk
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 implementation of convex dielectric lenses enhances the photo sensing quality by improving quantum efficiency and increasing the signal-to-noise ratio (SNR) of the image sensor device.
Implementation Method 1
a convex dielectric lens is formed in each pixel region between the color filter and the substrate... which condenses incident light into a photo-sensitive element
Data Source
AI summary
An image sensor device includes a semiconductor device, a plurality of photo sensitive regions, a dielectric layer, a grid structure, and a plurality of convex dielectric lenses. The photo sensitive regions are in the semiconductor substrate. The dielectric layer is over a backside surface of the semiconductor substrate. The grid structure is over a backside surface of the dielectric layer. The grid structure includes a plurality of grid lines. Each of the grid lines comprises a lower portion and an upper portion forming an interface with the lower portion. The convex dielectric lenses are alternately arranged with the grid lines over the backside surface of the dielectric layer. Apexes of the plurality of convex dielectric lenses are higher than an interface between the upper portion and the lower portion of each of the grid lines.