Ferroelectric BDTI Structure for Low-Dark-Current CMOS Pixels

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Solution Overview

Problem

CMOS pixel sensors face challenges with increased dark current and white pixel number due to interface defects near the edges of back-side deep trench isolation (BDTI) structures, which are exacerbated by process limitations that prevent reduction of critical BDTI structure dimensions.

Innovation Solution

Incorporating a ferroelectric layer within the BDTI structures of CMOS image sensors, which enhances dipole moments and reduces interaction between image sensing elements and interface defects, thereby decreasing dark current and improving white pixel number performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of moving object

If the critical dimensions of BDTI structures are reduced to improve pixel density, then device integration increases, but interface defects increase causing higher dark current and white pixel number

Engineering Contradiction:

Improvepixel densityVSAvoiddark current

Core Design Contradiction:

Area of moving objectVSObject-affected harmful factors

Solution Approach 1:

A ferroelectric layer is introduced as an intermediary between the BDTI structure and the pixel region. This layer passivates interface defects at the BDTI-pixel interface, reducing dark current and white pixel defects while allowing the BDTI structure to maintain its isolation function. The ferroelectric layer's dipole moments counteract the harmful effects of interface defects, enabling continued scaling without proportional increase in defects.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the electrical parameters at the BDTI interface by introducing a ferroelectric material with specific dielectric properties. The ferroelectric layer's polarization state and dipole moment are controlled to optimize the electrical characteristics at the interface, reducing carrier generation from defects while maintaining the structural integrity of the scaled-down BDTI features.

Inventive Principle:

Principle #35Parameter changes

2Area of moving object

If the critical dimensions of BDTI structures are reduced to improve pixel density, then device integration increases, but interface defects increase causing higher white pixel number

Engineering Contradiction:

Improvepixel densityVSAvoidwhite pixel number

Core Design Contradiction:

Area of moving objectVSReliability

Solution Approach 1:

The ferroelectric layer serves as a protective intermediary that passivates interface defects responsible for white pixel defects. By positioning this layer at the BDTI-pixel interface, it prevents direct interaction between scaling-induced interface defects and the pixel region, thereby reducing white pixel number while allowing continued miniaturization of the BDTI structures.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Manufacturing precision

If process limitations are overcome to reduce BDTI structure dimensions, then manufacturing precision improves, but interface defects worsen due to process variability

Engineering Contradiction:

ImproveBDTI structure dimensionsVSAvoidinterface defects

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The ferroelectric layer is applied beforehand to cushion against the harmful effects of interface defects that arise from process variability. This layer provides a buffer that passivates defects before they can significantly impact pixel performance, allowing the manufacturing process to achieve smaller dimensions even with inherent process variability.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The ferroelectric material acts as an intermediary layer that decouples the relationship between BDTI structure dimensions and interface defect impact. By introducing this intermediate layer, the system can achieve smaller feature sizes without a proportional increase in harmful interface effects, as the ferroelectric layer absorbs and passivates the defect-related stress.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 ferroelectric layer effectively reduces dark current and improves white pixel number performance by enhancing dipole moments within the BDTI structures, leading to improved image quality in digital imaging devices without adverse side effects.

Implementation Method 1

Incorporating a ferroelectric layer within the BDTI structures of CMOS image sensors, which enhances dipole moments

Methodology Applied

Scientific EffectFerroelectric effect:

Data Source

PatentUS12349493B2Semiconductor structure and manufacturing method of the same

Publication Date: 2025.07.01 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A semiconductor device, a back-side deep trench isolation (BDTI) structure of a semiconductor device, and method of manufacturing a semiconductor structure are provided. The semiconductor device, comprising: a pixel region disposed within a substrate and comprising an image sensing element configured to convert electromagnetic radiation into an electrical signal; and one or more BDTI structures extending from a first-side of the substrate to positions within the substrate; wherein the one or more of BDTI structures comprise one or more ferroelectric materials.