Semiconductor Structure Conductive Pad for BSI Image Sensor Quantum Efficiency

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Solution Overview

Problem

The manufacturing of back side illuminated (BSI) image sensors is complex and results in issues such as poor quantum efficiency, strip line defects, and increased costs due to rough and uneven surfaces during the deposition of color filters, which affects the sensitivity and accuracy of the image sensors.

Innovation Solution

An improved semiconductor structure is developed with a conductive pad surrounded by the semiconductive substrate, reducing the roughness of the back side and allowing for uniform deposition of thinner color filters, enhancing quantum efficiency and reducing material costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If conventional BSI image sensor manufacturing is used, then light sensitivity is improved, but manufacturing complexity increases and defects occur

Engineering Contradiction:

Improvelight sensitivityVSAvoidmanufacturing complexity

Core Design Contradiction:

Illumination intensityVSDevice complexity

Solution Approach 1:

The patent inverts the conventional manufacturing sequence by forming color filters on the back surface before substrate thinning, rather than after. This reversal allows the color filter deposition to occur on a thicker, more stable substrate, avoiding the rough and uneven surface problems that arise when depositing on thinned substrates, thereby reducing manufacturing complexity and defects while maintaining light sensitivity

Inventive Principle:

Principle #13The other way round (Inversion)

2Ease of manufacture

If color filters are deposited on thinned substrate, then integration is achieved, but surface roughness increases and quantum efficiency deteriorates

Engineering Contradiction:

ImproveintegrationVSAvoidsurface roughness

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent performs color filter deposition as a preliminary action before substrate thinning. By depositing color filters on the back surface of the substrate at an earlier stage when the substrate is still thick and stable, the process avoids the surface roughness and unevenness problems that occur when depositing on thinned substrates, thereby maintaining manufacturing precision while achieving integration

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If conventional deposition process is used, then color filters are formed, but material waste increases and costs rise

Engineering Contradiction:

Improvecolor filter formationVSAvoidmaterial waste

Core Design Contradiction:

Ease of manufactureVSLoss of substance

Solution Approach 1:

The patent inverts the deposition timing to occur before substrate thinning. This allows for more precise material application on a stable substrate surface, reducing material waste from defects, rework, and uneven deposition that characterize conventional post-thinning processes, thereby reducing both material waste and manufacturing costs

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS11018179B2Semiconductor structure

Publication Date: 2021.05.25 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A semiconductor structure includes an ILD disposed over a semiconductive substrate, an isolation disposed between the semiconductive substrate and the ILD, and a conductive pad disposed within the semiconductive substrate, the isolation and the ILD. A top surface of the conductive pad is substantially parallel with two surfaces of the semiconductive substrate. The top surface of the conductive pad is between the two surfaces of the semiconductive substrate. Sidewalls of the conductive pad are in direct contact with the ILD and the isolation.