Multi-Layer Metal Stack Layout for Image Sensor Crosstalk Control

Solution Overview

Problem

As image pixels become smaller, sensitivity to light decreases and electrical and optical crosstalk between adjacent pixels increases, affecting the performance of image sensors.

Innovation Solution

The use of multi-layer metal stacks for both active and black pixel regions, where the metal grid structure enhances light sensitivity and reduces crosstalk by directing light to active pixels while the light shield attenuates light to black pixels, using a common base number of metal layers to simplify fabrication.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If image pixels are reduced in size to increase resolution, then the resolution of the image sensor is improved, but light sensitivity decreases and crosstalk between adjacent pixels increases

Engineering Contradiction:

ImproveresolutionVSAvoidlight sensitivity

Core Design Contradiction:

Measurement precisionVSIllumination intensity

Solution Approach 1:

The patent segments the metal stack into region-specific configurations: a first metal stack for active pixel regions and a second metal stack for black pixel regions. This segmentation allows each region to have optimized metal layer structures that address their specific functional requirements, thereby improving light sensitivity without compromising resolution.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies local quality by providing different metal stack configurations in different regions of the image sensor. Active pixel regions receive a first metal stack design optimized for light guidance, while black pixel regions receive a second metal stack design optimized for light blocking. This localized optimization resolves the contradiction by allowing high resolution through small pixel size while maintaining light sensitivity through region-specific metal structures.

Inventive Principle:

Principle #3Local quality

2Measurement precision

If image pixels are reduced in size to increase resolution, then the resolution of the image sensor is improved, but crosstalk between adjacent pixels increases

Engineering Contradiction:

ImproveresolutionVSAvoidcrosstalk

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent segments the metal stack into region-specific configurations: a first metal stack for active pixel regions and a second metal stack for black pixel regions. This segmentation allows each region to have optimized metal layer structures that address their specific functional requirements, thereby improving light sensitivity without compromising resolution.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies local quality by providing different metal stack configurations in different regions of the image sensor. Active pixel regions receive a first metal stack design optimized for light guidance, while black pixel regions receive a second metal stack design optimized for light blocking. This localized optimization resolves the contradiction by allowing high resolution through small pixel size while maintaining light sensitivity through region-specific metal structures.

Inventive Principle:

Principle #3Local quality

3Illumination intensity

If different metal stack configurations are used for active and black pixel regions to optimize performance, then light sensitivity and crosstalk reduction are improved, but fabrication complexity increases

Engineering Contradiction:

Improvelight sensitivityVSAvoidfabrication complexity

Core Design Contradiction:

Illumination intensityVSDevice complexity

Solution Approach 1:

The patent applies universality by establishing a common base number of metal layers that serves both active and black pixel regions. This common foundation reduces fabrication complexity by standardizing the base structure, while region-specific additional layers provide the necessary functional differentiation for optimized light sensitivity and crosstalk reduction in each region type.

Inventive Principle:

Principle #6Universality (Multi-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

This approach enhances light sensitivity and reduces crosstalk, improving the overall performance of image sensors by tailoring the thickness and structure of the metal stacks for each region.

Implementation Method 1

the metal grid structure enhances light sensitivity and reduces crosstalk by directing light to active pixels

Methodology Applied

Scientific EffectLight reflection and refraction: Reflection

Implementation Method 2

the light shield attenuates light to black pixels

Methodology Applied

Scientific EffectLight absorption and attenuation: Absorption (EM radiation)

Data Source

PatentUS12080740B2Multi-layer metal stack for active pixel region and black pixel region of image sensor and methods thereof

Publication Date: 2024.09.03 OMNIVISION TECHNOLOGIES INC

AI summary

An image sensor includes an active pixel photodiode, a black pixel photodiode, a metal grid structure, and a light shield. Each of the active pixel photodiode and the black pixel photodiode are disposed in a semiconductor material having a first side and a second side opposite the first side. The first side of the semiconductor material is disposed between the light shield and the black pixel photodiode. The metal grid structure includes a first multi-layer metal stack including a first metal and a second metal different from the first metal. The light shield includes a second multi-layer stack including the first metal and the second metal. A first thickness of the first multi-layer metal stack is less than a second thickness of the second multi-layer metal stack.