Curved Sidewall Absorption Structure for Image Sensor Quantum Efficiency

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Solution Overview

Problem

CMOS image sensors face limitations in quantum efficiency due to the design of absorption enhancement structures with straight sidewalls, which reduce the light receiving surface area and mitigate the sensor's performance.

Innovation Solution

The implementation of an absorption enhancement structure with protrusions having curved sidewalls on the back-side surface of the semiconductor substrate, increasing the light receiving surface area and enhancing quantum efficiency by redirecting incident electromagnetic radiation towards the photodetector.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If absorption enhancement structures with straight sidewalls are used, then the manufacturing process is simpler, but the light receiving surface area is reduced and quantum efficiency deteriorates

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidlight receiving surface area

Core Design Contradiction:

Ease of manufactureVSArea of moving object

Solution Approach 1:

The patent applies curvature to the sidewalls of the absorption enhancement structures, transforming them from straight vertical walls to curved surfaces that bow outward. This curvature increases the light receiving surface area by creating a larger effective aperture for capturing incident photons, while the curved geometry still allows for standard semiconductor fabrication processes to be used.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Reliability

If protrusions with curved sidewalls are implemented, then the quantum efficiency is enhanced by increasing light receiving surface area, but the manufacturing precision requirements increase

Engineering Contradiction:

Improvequantum efficiencyVSAvoidsidewall curvature precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent optimizes specific geometric parameters of the curved sidewalls, including the radius of curvature, the height of protrusions, and the spacing between adjacent structures. By carefully selecting these parameters, the design achieves high quantum efficiency while remaining compatible with standard fabrication tolerances, thus balancing performance improvement with manufacturing feasibility.

Inventive Principle:

Principle #35Parameter changes

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 curved sidewall design increases the light receiving surface area, thereby enhancing the quantum efficiency of the image sensor, improving its ability to absorb photons and generate electric signals.

Implementation Method 1

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Implementation Method 2

redirecting incident electromagnetic radiation towards the photodetector

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS11600647B2Absorption enhancement structure to increase quantum efficiency of image sensor

Publication Date: 2023.03.07 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

Various embodiments of the present disclosure are directed towards an image sensor having a photodetector disposed within a substrate. The substrate has a front-side surface and a back-side surface. An absorption enhancement structure is disposed along the back-side surface of the substrate and overlies the photodetector. The absorption enhancement structure includes a plurality of protrusions that extend outwardly from the back-side surface of the substrate. Each protrusion comprises opposing curved sidewalls.