FinFET Fin Bending Mitigation via Multi-Step Etching

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Solution Overview

Problem

Existing FinFET devices and fabrication methods face challenges in achieving optimal performance and preventing fin bending due to uneven stress between dense and isolated fin regions, leading to potential structural damage and reduced device reliability.

Innovation Solution

A method involving the formation of fin structures with varying pitches and the use of multi-step etching processes to form liner and isolation features, where the flow rates of etching gases are adjusted to control the height of these features, preventing fin bending and maintaining the structural integrity of FinFETs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multi-step etching processes with adjusted gas flow rates are used to control liner and isolation feature height, then fin bending is prevented and structural integrity is maintained, but process complexity increases

Engineering Contradiction:

Improvestructural integrity of FinFETsVSAvoidetching process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The etching process is divided into multiple sequential steps, each targeting specific features (liner layer removal, isolation feature formation, mandrel removal). This segmentation allows precise control over the height and dimensions of each feature type, preventing fin bending by ensuring uniform stress distribution throughout the structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The process dynamically adjusts etching gas flow rates between different etching steps. By changing gas flow parameters, the etching rate and selectivity are optimized for each specific feature being formed, enabling precise height control of liner and isolation features while maintaining structural integrity.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If uniform etching processes are used for all fin regions, then manufacturing simplicity is maintained, but uneven stress distribution causes fin bending in dense versus isolated fin regions

Engineering Contradiction:

Improveetching process simplicityVSAvoidfin structure straightness

Core Design Contradiction:

Ease of manufactureVSShape

Solution Approach 1:

The etching process applies different gas flow rates to different regions and features based on their specific requirements. Isolated fins receive different etching conditions compared to dense fin regions, and liner layers are removed at different rates than isolation features. This local customization ensures uniform stress distribution and prevents fin bending while maintaining manufacturing feasibility.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If liner and isolation features are formed to uniform height, then manufacturing simplicity is maintained, but stress distribution becomes uneven causing fin bending

Engineering Contradiction:

Improvefeature height control simplicityVSAvoidstress distribution uniformity

Core Design Contradiction:

Ease of manufactureVSStability of the object's composition

Solution Approach 1:

The etching process transitions from static uniform etching to dynamic selective etching. Gas flow rates are adjusted in real-time during different etching steps to control the height of liner and isolation features differently. This dynamic approach ensures that features are formed to the precise heights needed for uniform stress distribution, preventing fin bending while remaining manufacturable.

Inventive Principle:

Principle #15Dynamics

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 effectively mitigates fin bending and maintains the structural integrity of FinFETs by controlling the height of liner and isolation features, ensuring consistent stress distribution and improved device performance.

Implementation Method 1

performing a multi-step etching process using a process gas comprising a first etching gas and a second etching gas. The multi-step etching process includes a first step of selectively removing the patterned hard mask structure and a second step of in-situ and selectively removing a portion of the insulating layer to form an isolation feature

Methodology Applied

Scientific EffectEtching:

Data Source

PatentUS10276449B1Method for forming fin field effect transistor (FinFET) device structure

Publication Date: 2019.04.30 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A method for forming a semiconductor device structure includes providing a substrate having a first fin structure and a second fin structure that are capped by a patterned hard mask structure. A liner layer and an overlying insulating layer are formed between the first and second fin structures. A multi-step etching process including a first step of selectively removing the patterned hard mask structure and a second step of in-situ and selectively removing a portion of the insulating layer to form an isolation feature is performed. The process gas used in the multi-step etching process includes a first etching gas and a second etching gas. The flow rate of the first etching gas is greater than that of the second etching gas in the first step and the flow rate of the first etching gas is less than that of the second etching gas in the second step.