BSI Image Sensor Backside Dielectrics for Petal Flare Suppression

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Solution Overview

Problem

Existing back side illuminated (BSI) image sensor devices suffer from petal flare and other defects due to constructive interference and feedback noise, resulting in reduced image quality with visible artifacts like starbursts and haze.

Innovation Solution

Incorporating one or more dielectric layers under the color filter layer with specific refractive indices and thicknesses to achieve destructive interference, reducing petal flare by tuning light waves and optimizing layer patterns across the wafer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If no dielectric layers are added on the backside, then the device structure remains simple, but petal flare and image quality defects occur due to constructive interference of light waves

Engineering Contradiction:

Improvestructure simplicityVSAvoidpetal flare and image quality defects

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful constructive interference into beneficial destructive interference by introducing dielectric layers with specific refractive indices and thicknesses. These layers create optical path differences that cause destructive interference of reflected light waves, thereby eliminating petal flare and improving image quality.

Inventive Principle:

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

Solution Approach 2:

The dielectric layers act as intermediary elements between the semiconductor substrate and the external environment. By selecting materials with appropriate refractive indices (such as silicon oxide, silicon nitride, or silicon oxynitride), these intermediate layers modify the optical interference characteristics without requiring fundamental changes to the sensor structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If dielectric layers with specific refractive indices and thicknesses are incorporated, then petal flare is reduced through destructive interference, but the device structure and fabrication process become more complex

Engineering Contradiction:

Improvepetal flare reductionVSAvoiddielectric layer structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent systematically varies key parameters including the number of dielectric layers (one or more), their thicknesses (tuned to achieve destructive interference at specific wavelengths), and material compositions (different refractive indices). By optimizing these parameters, the patent achieves effective petal flare reduction while managing structural complexity.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If the thickness and material composition of dielectric layers are optimized, then light interference is controlled to enhance image quality, but the fabrication process becomes more difficult

Engineering Contradiction:

Improveimage quality and light interference controlVSAvoidfabrication process difficulty

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The dielectric layers are formed using standard semiconductor fabrication techniques such as chemical vapor deposition (CVD) or atomic layer deposition (ALD) before subsequent processing steps. The thickness and composition are predetermined based on optical design calculations, allowing the fabrication process to proceed systematically without requiring complex post-fabrication adjustments.

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 effectively minimizes petal flare issues, leading to improved image quality with reduced noise and enhanced contrast and color saturation.

Implementation Method 1

Incorporating one or more dielectric layers with specific refractive indices and thicknesses to achieve destructive interference of light waves, reducing petal flare by tuning the light interference.

Methodology Applied

Scientific EffectDestructive interference: Interference

Data Source

PatentUS20240006458A1Back side illuminated image sensor device with select dielectric layers on the backside and methods of forming the same

Publication Date: 2024.01.04 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

An image sensor device is disclosed which includes a semiconductor layer having a first surface and a second surface, where the second surface is opposite to the first surface. The device includes a conductive structure disposed over the first surface, with a dielectric layer disposed between the conductive structure and the first surface. The device includes a first dielectric layer disposed over the second surface of the semiconductor substrate. The device includes a second dielectric layer disposed over the first dielectric layer. The device includes a color filter layer disposed over the second dielectric layer. In some embodiments, the thickness, refractive index, or both of the first dielectric layer and the thickness, refractive index, or both of the second dielectric layer may be collectively determined to cause incident radiation passing through the first dielectric layer and the second dielectric layer and to the plurality of pixels to have destructive interference.