Silicon Waveguide Side Slab Prevents Etching Tapering

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Solution Overview

Problem

During the etching process for forming recesses in photonic devices, the silicon waveguide tends to taper due to photoresist shrinkage and lateral etching, leading to wave intensity loss and reduced total internal reflection, which can cause the device to fail.

Innovation Solution

A side slab structure is deposited on the cladding layer before etching the lower dielectric and silicon substrate, preventing tapering of the waveguide and improving wave intensity and total internal reflection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If etching is performed to form recesses for photonic devices, then the recesses are successfully formed, but the silicon waveguide tapers due to photoresist shrinkage and lateral etching

Engineering Contradiction:

Improvewaveguide profile precisionVSAvoidwaveguide tapering

Core Design Contradiction:

Manufacturing precisionVSShape

Solution Approach 1:

The cladding layer is etched to form a recess and the side slab is formed on the cladding layer surface before etching the silicon waveguide. This preliminary action establishes a protective structure that prevents lateral etching of the waveguide sidewalls, thereby maintaining waveguide profile precision while forming the necessary recesses.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The side slab acts as an intermediary protective structure between the etching process and the silicon waveguide. By placing the side slab on the cladding layer surface, it serves as a barrier that prevents photoresist shrinkage and lateral etching from affecting the waveguide profile, thus resolving the contradiction between forming recesses and maintaining waveguide shape.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If the waveguide tapers during etching, then the etching process completes, but wave intensity is lost and total internal reflection is reduced

Engineering Contradiction:

Improveetching completionVSAvoiddevice efficiency

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The side slab is formed on the cladding layer surface before etching the silicon waveguide. This preliminary protective structure ensures that when etching proceeds to complete the recess formation, the waveguide profile remains intact, thereby maintaining wave intensity and total internal reflection while still achieving etching completion.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The side slab serves as a protective intermediary that allows the etching process to complete successfully while preventing the harmful lateral etching that would otherwise reduce wave intensity and total internal reflection. This mediator enables both etching completion and device efficiency to be maintained.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Manufacturing precision

If photoresist is used for patterning, then the patterning process is achieved, but photoresist shrinkage causes lateral etching of the waveguide

Engineering Contradiction:

Improvepatterning accuracyVSAvoidlateral etching

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The side slab acts as a protective intermediary structure that blocks lateral etching from reaching the silicon waveguide. By placing the side slab on the cladding layer surface, it intercepts the harmful lateral etching caused by photoresist shrinkage, thereby maintaining patterning accuracy while preventing waveguide damage.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The side slab structure provides self-protection to the silicon waveguide against lateral etching. The cladding layer is etched to form the recess, and the side slab is formed on its surface, creating a self-contained protective system that eliminates the need for additional protective measures during the waveguide etching process.

Inventive Principle:

Principle #25Self-service

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 side slab structure enhances the efficiency of photonic devices by maintaining wave intensity and total internal reflection, preventing device failure and improving overall performance.

Implementation Method 1

a side slab over the sidewall surface of the cladding layer... The side slab prevents tapering of the silicon waveguide during etching of the lower dielectric and the substrate

Methodology Applied

Scientific EffectPhysical barrier protection:

Implementation Method 2

The side slab prevents tapering of the silicon waveguide during etching of the lower dielectric and the substrate, which maintains total internal reflection and wave intensity

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Data Source

PatentUS12259576B2Semiconductor waveguides and methods of forming the same

Publication Date: 2025.03.25 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

Depositing a side slab structure on a cladding layer before etching a supporting dielectric prevents tapering of a silicon waveguide during etching of the supporting dielectric and a substrate. For example, the side slab structure may be deposited over the silicon waveguide and the cladding layer after etching the cladding layer. As a result, when an electronic device is integrated ex situ on the substrate, wave intensity and/or total internal reflection is improved, which improves an efficiency of the electronic device.