Flicker-Mitigating Pixel-Array Substrate With Metal Annulus
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Solution Overview
Problem
Cameras installed on motor vehicles suffer from flicker artifacts and petal flare due to the periodicity of their image sensor pixel and microlens arrays, which are exacerbated by the flickering daytime running lights and diffraction effects.
Innovation Solution
Integration of a metal film above the pixel's photodiode with a metal annulus that fills the trench surrounding the small photodiode, attenuating incident light and mitigating saturation and diffraction issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal film is integrated with a metal annulus to attenuate incident light and mitigate saturation, then flicker artifacts are reduced, but device complexity increases
Solution Approach 1:
The patent merges the metal film (first metal layer) with the metal annulus (second metal layer) by making them integrally connected or adjacent, forming a unified light-attenuating structure. This integration allows the combination to function as a single element for mitigating flicker artifacts and petal flare, while reducing manufacturing steps compared to separate applications.
Solution Approach 2:
The metal film acts as an intermediary layer between the photodiode and incident light, selectively attenuating light at specific wavelengths (particularly in the blue region around 450nm) before it reaches the photodiode. This intermediary structure prevents saturation during integration operations without completely blocking useful light signal.
2Ease of manufacture
If the pixel array periodicity is maintained for compact design, then manufacturing is simplified, but petal flare artifacts increase due to diffraction effects
Solution Approach 1:
The patent extracts or removes the harmful diffracted light paths by introducing metal annulus structures that surround each pixel's photodiode. These annulus structures selectively block light that has been diffracted by the periodic pixel array, preventing it from reaching adjacent pixels and causing petal flare artifacts.
Solution Approach 2:
The patent applies local quality by making the metal annulus structure specific to each pixel region, with the annulus surrounding only the small photodiode. This localized approach allows the periodic pixel array to maintain its compact design while each individual pixel region has tailored light-blocking properties to prevent petal flare.
3Adaptability or versatility
If a small photodiode is used for bright-light detection, then dynamic range is improved, but saturation occurs during integration operations under daytime running lights
Solution Approach 1:
The patent changes the optical parameters of the small photodiode by introducing the metal film layer above it. This metal layer modifies the light transmission characteristics, attenuating specific wavelengths (particularly blue light around 450nm) to prevent the photodiode from saturating during integration operations while maintaining its small size and bright-light detection capability.
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 flicker artifacts and petal flare by preventing small photodiode saturation and absorbing diffracted light, thereby improving image sensor sensitivity and quality.
Implementation Method 1
A metal layer is disposed covering a light exposure surface of the small photodiode. The metal layer attenuates incident light propagating toward the small photodiode, which prevents the small photodiode from reaching saturation during an integration operation
Implementation Method 2
The periodicity of the image sensor's pixel array and microlens array thereon results in the image sensor resembling a reflective two-dimensional diffraction grating. Part of light incident on the image sensor is diffracted toward the camera's imaging lens
Implementation Method 3
The metal annulus (i) at least partially fills the trench, (ii) surrounds the small-photodiode region in the cross-sectional plane, and (iii) extends above the back surface... absorbing diffracted light
Data Source
AI summary
A flicker-mitigating pixel-array substrate includes a semiconductor substrate and a metal annulus. The semiconductor substrate includes a small-photodiode region. A back surface of the semiconductor substrate forms a trench surrounding the small-photodiode region in a cross-sectional plane parallel to a back-surface region of the back surface above the small-photodiode region. The metal annulus (i) at least partially fills the trench, (ii) surrounds the small-photodiode region in the cross-sectional plane, and (iii) extends above the back surface. A method for fabricating a flicker-mitigating pixel-array substrate includes forming a metal layer (i) in a trench that surrounds the small-photodiode region in a cross-sectional plane parallel to a back-surface region of the back surface above the small-photodiode region and (ii) on the back-surface region. The method also includes decreasing a thickness of an above-diode section of the metal layer located above the back-surface region.