FinFET Fin Isolation Structure for CMP Endpoint Stability

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Solution Overview

Problem

Existing FinFET manufacturing processes face challenges in forming effective isolation structures for adjacent fins, leading to issues such as increased fin loss during chemical mechanical polishing due to the reaction between nitrogen-containing capping layers and polishing slurry, which affects the fin height and integrity.

Innovation Solution

A dual capping structure is implemented, comprising a nitrogen-free second capping layer that mitigates the reaction with the polishing slurry, ensuring precise endpoint detection and preventing fin loss by maintaining the polishing process on the top surfaces of the fins, while a nitrogen-containing first capping layer serves as an etching stop.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a nitrogen-containing capping layer is used, then etching selectivity is improved, but fin loss increases during chemical mechanical polishing

Engineering Contradiction:

Improveetching selectivityVSAvoidfin height consistency

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The capping layer is segmented into two distinct layers: a first capping layer containing nitrogen for etching selectivity, and a second capping layer free of nitrogen to prevent harmful reactions during CMP. This segmentation allows each layer to perform its specific function without interfering with the other, resolving the contradiction between etching performance and polishing stability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second capping layer acts as an intermediary protective layer between the nitrogen-containing first capping layer and the polishing slurry. It prevents direct contact between the slurry and nitrogen-containing materials, thereby preventing pH changes and fin loss during CMP while allowing the first capping layer to maintain etching selectivity.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If a single capping layer is used, then process complexity is reduced, but endpoint detection precision deteriorates

Engineering Contradiction:

Improvecapping layer structureVSAvoidpolishing endpoint detection

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The second capping layer is configured to reflect light, creating a detectable optical signal during CMP. This optical property enables precise endpoint detection through light reflection monitoring, allowing the polishing process to be accurately controlled without requiring complex multi-material structures.

Inventive Principle:

Principle #32Color changes

3Ease of manufacture

If the capping layer reacts with polishing slurry, then etching performance is enhanced, but fin loss increases during polishing

Engineering Contradiction:

Improveetching performanceVSAvoidfin loss during CMP

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

The harmful nitrogen component is extracted from the second capping layer that contacts the polishing slurry, while being retained in the first capping layer where it provides etching performance. This selective extraction eliminates the harmful reaction during CMP while preserving the beneficial etching properties.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The nitrogen-containing first capping layer, which would normally cause harmful reactions during CMP, is protected by the nitrogen-free second layer. The nitrogen's etching benefits are preserved while its harmful polishing effects are converted into a controlled situation where it does not contact the slurry directly.

Inventive Principle:

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

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 dual capping structure effectively controls the polishing endpoint, reducing fin loss and ensuring consistent fin height, thereby enhancing the reliability and performance of FinFET devices.

Implementation Method 1

a nitrogen-free second capping layer that mitigates the reaction with the polishing slurry, ensuring precise endpoint detection

Methodology Applied

Scientific EffectChemical reaction prevention:

Implementation Method 2

ensuring precise endpoint detection and preventing fin loss by maintaining the polishing process on the top surfaces of the fins

Methodology Applied

Scientific EffectEndpoint detection:

Implementation Method 3

increased fin loss during chemical mechanical polishing due to the reaction between nitrogen-containing capping layers and polishing slurry

Methodology Applied

Scientific EffectChemical mechanical polishing:

Data Source

PatentUS12543365B2Fin isolation structure for FinFET and method of forming the same

Publication Date: 2026.02.03 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A semiconductor device structure is provided. The semiconductor device structure includes an isolation feature formed over a substrate that includes a first fin and a second fin separated from each other by the isolation feature. The semiconductor device structure also includes an insulating fin structure formed in the isolation feature between the first fin and the second fin. The insulating fin structure includes a first insulating fin base partially formed within the isolation feature and a first insulating capping layer formed over a top surface of the first insulating fin base.