Curved Light Blocking Structures in Image Sensors

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Solution Overview

Problem

Current image sensor devices face challenges with crosstalk between adjacent pixel regions, leading to reduced quantum efficiency and increased dark current and white pixel issues, which affect the performance and reliability of the devices.

Innovation Solution

The implementation of embedded light blocking structures in the semiconductor substrate, formed by creating recesses using an isotropic etching process and filling them with a light blocking material, helps prevent crosstalk by blocking light between adjacent pixel regions, thereby improving quantum efficiency and reducing dark current and white pixel issues.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If light blocking structures are implemented to reduce crosstalk, then quantum efficiency is improved, but device complexity increases

Engineering Contradiction:

Improvequantum efficiencyVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The semiconductor substrate is divided into isolated pixel regions by light blocking structures formed between adjacent pixels. This segmentation prevents optical crosstalk between neighboring pixels while maintaining individual pixel functionality, thereby improving quantum efficiency without requiring complete redesign of the sensor architecture.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Light blocking structures serve as intermediary elements positioned between adjacent pixel regions. These structures act as optical barriers that block stray light and prevent crosstalk, allowing each pixel to accurately detect only its intended light signal while maintaining close spacing for high pixel density.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If conventional light blocking methods are used, then crosstalk is reduced, but manufacturing precision requirements increase

Engineering Contradiction:

Improvecrosstalk reductionVSAvoidmanufacturing precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The light blocking structures are formed with curved sidewalls rather than vertical or angled profiles. This curvature is achieved through isotropic etching processes that naturally produce rounded profiles, reducing sensitivity to alignment variations and simplifying manufacturing while maintaining effective light blocking between pixels.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The invention changes the etching parameters to achieve isotropic etching behavior, which produces curved sidewalls in the light blocking structures. This parameter change from anisotropic to isotropic etching reduces manufacturing precision requirements while maintaining effective crosstalk suppression.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If aggressive etching is used to form light blocking structures, then crosstalk prevention is improved, but substrate damage increases

Engineering Contradiction:

Improvecrosstalk preventionVSAvoidsubstrate damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention converts the potential harm of aggressive etching into a benefit by using controlled isotropic etching to form curved sidewalls. The same etching conditions that could cause damage are instead used to create a beneficial curved profile that reduces stress concentration and prevents substrate damage while maintaining effective light blocking.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The curved sidewall profile formed by isotropic etching acts as a cushioning feature that prevents stress concentration at sharp corners. This beforehand geometric modification reduces the risk of substrate damage during subsequent processing steps and device operation, while still maintaining effective light blocking functionality.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 use of light blocking structures effectively reduces crosstalk and associated issues, enhancing the yield and performance of image sensor devices by minimizing damage during the formation process and improving the overall reliability of the devices.

Implementation Method 1

creating recesses using an isotropic etching process

Methodology Applied

Scientific EffectIsotropic etching:

Implementation Method 2

filling them with a light blocking material, helps prevent crosstalk by blocking light between adjacent pixel regions

Methodology Applied

Scientific EffectLight blocking: Absorption (EM radiation)

Data Source

PatentUS9324752B2Image sensor device with light blocking structure

Publication Date: 2016.04.26 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

The disclosure provides an image sensor device and a manufacturing method. The image sensor device includes a semiconductor substrate and a light sensing region in the semiconductor substrate. The image sensor device also includes a light blocking structure in the semiconductor substrate and adjacent to the light sensing region. A sidewall of the light blocking structure is a curved surface.