Back-illuminated CMOS Image Sensor Light Shielding for Parasitic Sensitivity

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Solution Overview

Problem

Back-illuminated CMOS image sensors with global shutter function face challenges in preventing parasitic light sensitivity (PLS) due to light leakage into the charge holding section.

Innovation Solution

Incorporating a light shielding section with a first light shielding surface extending from between the charge holding section and the photoelectric converter, which effectively blocks light entry into the charge holding section, thereby suppressing PLS.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the charge holding section is stacked on the photoelectric converter to achieve global shutter function, then the global shutter capability is improved, but light leakage into the charge holding section occurs causing parasitic light sensitivity

Engineering Contradiction:

Improveglobal shutter capabilityVSAvoidparasitic light sensitivity

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The light shielding section is divided into multiple surfaces (first light shielding surface and second light shielding surface) that segment the light blocking function. The first light shielding surface extends from between the charge holding section and photoelectric converter, while the second light shielding surface is positioned between the charge holding section and photoelectric converter, together forming a comprehensive light shielding structure that prevents parasitic light sensitivity while maintaining global shutter capability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The light shielding section acts as an intermediary element positioned between the photoelectric converter and charge holding section. This intermediate structure blocks light paths that would otherwise cause parasitic light sensitivity in the charge holding section, while allowing the global shutter function to operate normally

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If the light shielding section is added to prevent light leakage, then parasitic light sensitivity is suppressed, but device complexity increases

Engineering Contradiction:

Improveparasitic light sensitivityVSAvoidstructure complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The light shielding section is merged with the charge holding section or photoelectric converter structure, forming an integrated component rather than a separate added element. This merging approach reduces device complexity while still providing effective light shielding to suppress parasitic light sensitivity

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The light shielding section serves multiple functions: it blocks light leakage to prevent parasitic light sensitivity, maintains the stacked structure between photoelectric converter and charge holding section, and supports the global shutter operation. This multi-functionality reduces the need for additional separate components

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

The implementation of the light shielding section significantly reduces light leakage into the charge holding section, effectively preventing parasitic light sensitivity and enhancing the imaging device's performance.

Implementation Method 1

a light shielding section that includes a first light shielding surface extending toward the charge holding section from between the charge holding section and the photoelectric converter

Methodology Applied

Scientific EffectLight shielding: Absorption (EM radiation)

Data Source

PatentUS11728361B2Imaging device and manufacturing method thereof

Publication Date: 2023.08.15 SONY SEMICON SOLUTIONS CORP

AI summary

An imaging device includes a photoelectric converter, a charge holding section that is provided on a side of the photoelectric converter opposite to a light entrance side of the photoelectric converter and holds a signal charge generated by the photoelectric converter, and a light shielding section that has a first light shielding surface extending toward the charge holding section from between the charge holding section and the photoelectric converter.