Pixel Layout With Optical Waveguides for Higher Image Sensor Sensitivity
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Solution Overview
Problem
In solid-state imaging devices, the reduction in pixel size leads to inefficient light transmission to photodiodes, resulting in decreased sensitivity, and overlapping color filters create non-effective regions, causing shading and reduced light collection efficiency.
Innovation Solution
A solid-state imaging device with photodiodes formed separately for each pixel on a semiconductor substrate, an insulating film with optical waveguides covering the photodiodes, and color filters arranged in specific layouts to minimize overlapping, with on-chip lenses formed on the color filters to enhance light collection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If pixel size is reduced, then the number of pixels increases, but light transmission efficiency to photodiodes decreases, resulting in lower sensitivity
Solution Approach 1:
The patent introduces an optical waveguide layer positioned between the color filter and the photodiode to create a new optical path dimension. This waveguide structure guides incident light laterally to the photodiode, compensating for the reduced light collection area caused by smaller pixel dimensions, thereby maintaining light transmission efficiency while increasing pixel density
Solution Approach 2:
The optical waveguide acts as an intermediary component that mediates between the color filter and the photodiode. It captures light after it passes through the color filter and redirects it to the photodiode, ensuring efficient light transmission even when the photodiode area is reduced due to smaller pixel size
2Area of stationary object
If color filters are arranged in conventional patterns, then all pixels can be covered, but overlapping regions create non-effective areas, causing shading and reduced light collection efficiency
Solution Approach 1:
The patent segments the pixel array into different types (first pixels with green color filters and second pixels with other color filters) and arranges them in a specific non-overlapping pattern. This segmentation approach allows each color filter to be positioned optimally without creating overlapping regions, eliminating non-effective areas and improving overall light collection efficiency
Solution Approach 2:
The patent employs an asymmetric arrangement where first pixels and second pixels are positioned in a specific pattern that prevents color filter overlap. This asymmetric layout optimizes the positioning of optical waveguides and color filters, ensuring that light transmission paths do not intersect and creating no non-effective regions
3Adaptability or versatility
If multiple wiring layers are added to peripheral circuits, then circuit functionality increases, but the distance from semiconductor substrate to OCL increases, lowering light collection efficiency
Solution Approach 1:
The patent positions the optical waveguide above the peripheral circuit wiring layers, utilizing the vertical space that would otherwise be wasted. By creating a three-dimensional optical path that extends above the wiring structure, the design maintains efficient light collection while accommodating complex multi-layer peripheral circuits
Solution Approach 2:
The optical waveguide is positioned to nest above the peripheral circuit wiring structure, utilizing the vertical space created by the multi-layer wiring. This nested arrangement allows the optical components to coexist with complex peripheral circuits without interfering with each other, maintaining light collection efficiency while supporting enhanced circuit functionality
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 reduces non-effective regions, enhances sensitivity by improving light collection efficiency, and maintains high sensitivity for green pixels, which are most sensitive to human vision, thereby improving image luminance data.
Implementation Method 1
an optical waveguide configured to guide incident light to the photodiode
Implementation Method 2
an on-chip lens configured to focus incident light on the photodiode
Implementation Method 3
a photodiode configured to convert incident light into an electrical signal
Data Source
AI summary
A solid-state imaging device includes a semiconductor substrate; and a pixel unit having a plurality of pixels on the semiconductor substrate, wherein the pixel unit includes first pixel groups having two or more pixels and second pixel groups being different from the first pixel groups, wherein a portion of the pixels in the first pixel groups and a portion of the pixels in the second pixel groups share a floating diffusion element.