Image Sensor Wave Guide Etching Using Wiring Layer as Stop

Solution Overview

Problem

Conventional image sensors with wave guides face issues of etching non-uniformity and plasma ion defects, leading to poor characteristics and dark current generation during the manufacturing process.

Innovation Solution

A method where a wiring layer is formed over the photodiode to serve as an etch stop layer, preventing non-uniform etching and discharging plasma-charged ions to the semiconductor substrate, thereby minimizing defects and improving light transfer efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If a wave guide is formed by etching the interlayer dielectric directly over the photodiode, then the light sensitivity is improved, but etching uniformity cannot be secured and plasma ions are introduced into the photodiode causing dark current

Engineering Contradiction:

Improvelight sensitivityVSAvoidetching uniformity

Core Design Contradiction:

Illumination intensityVSManufacturing precision

Solution Approach 1:

A wiring layer is formed over the photodiode before the wave guide etching process. This wiring layer serves as a preliminary protective structure that will act as an etch stop layer during subsequent etching, preventing direct exposure of the photodiode to plasma ions while maintaining the intended etching depth and uniformity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The wiring layer is introduced as an intermediary element between the etching process and the photodiode. It functions as a mediator that stops the etching process before plasma ions can reach the photodiode, thereby protecting the photodiode from ion damage while still allowing the wave guide to be formed in the interlayer dielectric above it.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Illumination intensity

If a wave guide is formed by etching the interlayer dielectric directly over the photodiode, then the light sensitivity is improved, but plasma ions are introduced into the photodiode causing dark current generation

Engineering Contradiction:

Improvelight sensitivityVSAvoiddark current

Core Design Contradiction:

Illumination intensityVSObject-generated harmful factors

Solution Approach 1:

The wiring layer is introduced as an intermediary element between the etching process and the photodiode. It functions as a mediator that stops the etching process before plasma ions can reach the photodiode, thereby protecting the photodiode from ion damage while still allowing the wave guide to be formed in the interlayer dielectric above it.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The wiring layer, which is a necessary component for electrical connections, is utilized in an unexpected way to protect the photodiode from plasma ion damage during etching. This converts a routine structural element into a protective barrier, turning a potential source of harm (plasma ion exposure) into a controlled process with beneficial outcomes.

Inventive Principle:

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

3Productivity

If the interlayer dielectric is etched to form a wave guide, then light transfer efficiency is improved, but etching non-uniformity leads to poor photodiode characteristics

Engineering Contradiction:

Improvelight transfer efficiencyVSAvoidphotodiode characteristics

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

A wiring layer is formed over the photodiode before the wave guide etching process. This wiring layer serves as a preliminary protective structure that will act as an etch stop layer during subsequent etching, preventing direct exposure of the photodiode to plasma ions while maintaining the intended etching depth and uniformity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The wiring layer is introduced as an intermediary element between the etching process and the photodiode. It functions as a mediator that stops the etching process before plasma ions can reach the photodiode, thereby protecting the photodiode from ion damage while still allowing the wave guide to be formed in the interlayer dielectric above it.

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

This approach ensures uniform etching and reduces dark current generation, enhancing the imaging characteristics of the image sensor by preventing plasma ion introduction into the photodiode.

Implementation Method 1

a separate wiring layer is formed over a photodiode so that etching uniformity is secured and the generation of dark current by plasma ions during an etching process is prevented when forming a wave guide through etching

Methodology Applied

Scientific EffectEtching:

Implementation Method 2

the generation of dark current by plasma ions during an etching process is prevented when forming a wave guide through etching

Methodology Applied

Scientific EffectPlasma: Plasma

Data Source

PatentEP2242105B1Image sensor having wave guide and method for manufacturing the same

Publication Date: 2016.12.21 SK HYNIX INC

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AI summary

An image sensor (200) having a wave guide (29) includes a semiconductor substrate (20) formed with a photodiode (21) and a peripheral circuit region; an anti-reflective layer (22) formed on the semiconductor substrate; an insulation layer (22-1) formed on the anti-reflective layer; a wiring layer (25) formed on the insulation layer and connected to the semiconductor substrate; at least one interlayer dielectric (26) stacked on the wiring layer; and a wave guide connected to the insulation layer by passing through the interlayer dielectric and the wiring layer which are formed over the photodiode.