FSI Image Sensor Metal Shield Structure for Stray Light Blocking

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Solution Overview

Problem

Existing image sensor device structures face inefficiencies in global shutter mode due to unwanted stray light exposure, leading to crosstalk and reduced quantum efficiency, particularly in the storage region and storage gate structures.

Innovation Solution

A front side illuminated (FSI) image sensor device structure is developed with a metal shield structure that covers the top surface and sidewall surfaces of the storage gate structure, formed using a conductive material with optimal thickness and etching processes to prevent light entry, and is electrically connected to a conductive structure through a via to ensure effective shielding and charge transfer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a metal shield structure is added to cover the storage gate structure, then light blocking performance is improved and quantum efficiency is enhanced, but device complexity and manufacturing difficulty increase

Engineering Contradiction:

Improvelight blocking performanceVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The shield structure is divided into multiple segments including a first shield structure covering the pixel region and a second shield structure covering the storage region. This segmentation allows each shield to be optimized independently for its specific function while reducing overall manufacturing complexity compared to a single monolithic shield.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different shield structures are applied to different regions of the device based on local requirements. The pixel region receives a first shield structure with specific properties, while the storage region receives a second shield structure with different properties, optimizing light blocking performance for each region's specific function.

Inventive Principle:

Principle #3Local quality

2Reliability

If the metal shield structure is formed with optimal thickness using etching processes, then light blocking performance is improved, but manufacturing precision requirements increase

Engineering Contradiction:

Improvelight blocking performanceVSAvoidmanufacturing precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The shield structures extend beyond the minimum required coverage areas to ensure complete light blocking. The first shield structure covers not only the pixel region but also portions of the storage region, and the second shield structure provides additional coverage, ensuring that no stray light can reach sensitive areas even with manufacturing tolerances.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The thickness and material composition of the shield structures are optimized to achieve effective light blocking at practical manufacturing tolerances. By adjusting these parameters, the design achieves sufficient light blocking performance without requiring extreme manufacturing precision.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the metal shield structure covers both top surface and sidewall surfaces of the storage gate structure, then stray light prevention is improved, but device complexity and manufacturing difficulty increase

Engineering Contradiction:

Improvestray light preventionVSAvoidease of manufacture

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The shield structures are designed to extend in multiple dimensions - both vertically (covering top surfaces) and laterally (covering sidewall surfaces). This multi-dimensional coverage ensures that stray light from any direction is blocked, while the segmented design maintains manufacturability by allowing each dimensional extension to be formed using standard semiconductor fabrication processes.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 metal shield structure enhances light blocking, improves quantum efficiency, and increases global shutter efficiency by preventing stray light from entering the storage region and storage gate, thereby reducing crosstalk and enhancing overall image sensor performance.

Implementation Method 1

The metal shield structure covers a top surface and sidewall surfaces of the storage gate structure to prevent unwanted stray light from entering the storage gate structure and/or the storage region

Methodology Applied

Scientific EffectLight blocking: Absorption (EM radiation)

Implementation Method 2

The electrical signal is used to display a corresponding image on a monitor or provide information about the optical image

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS10868065B2Front side illuminated image sensor device structure and method for forming the same

Publication Date: 2020.12.15 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

An FSI image sensor device structure is provided. The FSI image sensor device structure includes a pixel region formed in a substrate and a storage region formed in the substrate and adjacent to the pixel region. The FSI image sensor device structure further includes a first gate structure formed over the storage region and a metal shield structure formed over the first gate structure. The FSI image sensor device structure further includes a conductive structure formed adjacent to the first gate structure. In addition, the conductive structure is electrically connected to the metal shield structure through a via.