CMOS Image Sensor Pixel Isolation Structure for Lower Optical Cross-Talk

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Solution Overview

Problem

Existing CMOS image sensors face challenges in achieving high performance and yield due to issues with pixel isolation and photoelectric conversion efficiency, leading to issues such as optical cross-talk and reduced light collection efficiency.

Innovation Solution

The image sensor incorporates a pixel isolation pattern with a layered structure comprising insulating and conductive films stacked on the inner walls of pixel isolation trenches, including different materials for the first and second material films, which enhances pixel isolation and improves light collection efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a simple pixel isolation structure is used, then manufacturing complexity is reduced, but optical cross-talk between adjacent pixels increases and light collection efficiency decreases

Engineering Contradiction:

Improvepixel isolation structure complexityVSAvoidoptical cross-talk

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The pixel isolation pattern uses a composite structure with multiple insulating films (first insulating film, second insulating film) and conductive films (first material film, second material film, gap fill conductive film) stacked together. This composite structure provides both electrical isolation and optical isolation functions, effectively reducing optical cross-talk while maintaining manufacturing feasibility through standardized film deposition processes.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The pixel isolation pattern extends into the vertical dimension by stacking multiple films with different materials and properties. The first insulating film, first material film, second insulating film, second material film, and gap fill conductive film are sequentially stacked to create a multi-layer isolation structure that addresses optical cross-talk from multiple depths, thereby improving isolation effectiveness without significantly increasing lateral complexity.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Object-affected harmful factors

If a multi-layer pixel isolation pattern is implemented, then optical cross-talk is reduced and light collection efficiency is improved, but manufacturing process complexity increases

Engineering Contradiction:

Improveoptical cross-talkVSAvoidpixel isolation structure complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

Different films in the pixel isolation pattern serve specific local functions: the first insulating film provides base isolation, the first material film adds conductive properties in specific regions, the second insulating film provides additional dielectric layers, the second material film adds further functional properties, and the gap fill conductive film specifically addresses gap regions. This localized functional assignment optimizes performance while keeping each layer's purpose clear and manufacturable.

Inventive Principle:

Principle #3Local quality

3Object-affected harmful factors

If pixel isolation trenches are deeply etched, then pixel isolation effectiveness is improved, but manufacturing precision requirements increase and yield decreases

Engineering Contradiction:

Improveoptical cross-talkVSAvoidtrench etching precision

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The pixel isolation trenches are pre-formed with defined depths and widths before the multi-layer film stacking process. By establishing the trench structure first, subsequent film deposition can proceed with standard thicknesses without requiring ultra-precise depth control during later processing steps. This preliminary trench formation separates the isolation depth requirement from the film deposition precision requirement, improving overall manufacturing yield.

Inventive Principle:

Principle #10Preliminary action

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 increases the performance and yield of the image sensor by reducing optical cross-talk and enhancing light collection, resulting in improved image quality and reliability.

Implementation Method 1

a photoelectric conversion region inside each of the unit pixels

Methodology Applied

Scientific EffectPhotoelectric conversion: Photoelectric Effect

Data Source

PatentUS20250311461A1Image sensor and method for fabricating the same

Publication Date: 2025.10.02 SAMSUNG ELECTRONICS CO LTD

AI summary

A CMOS type image sensor includes a substrate that includes a first side and a second side that are opposite to each other, a pixel isolation pattern that defines a plurality of unit pixels that are two-dimensionally arranged inside the substrate, and a photoelectric conversion region inside each of the unit pixels. The pixel isolation pattern includes a first insulating film, a first material film, a second insulating film, a second material film, and a gap fill conductive film that are sequentially stacked on an inner wall of the substrate. One end of the first material film adjacent to the first side and one end of the second material film adjacent to the first side are each in contact with the gap fill conductive film, and the first material film and the second material film include a different material from the first insulating film and the second insulating film.