FinFET Source/Drain Epitaxy With Rounded Tops for Region Separation

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Solution Overview

Problem

As semiconductor devices transition to nanometer technology process nodes, challenges arise in forming source/drain regions for FinFETs, including nodule defects, non-merging of intra-fin epitaxial regions, and increased contact resistance, which affect device performance and production throughput.

Innovation Solution

An epitaxial scheme is employed to form source/drain regions with rounded top profiles, utilizing a carrier gas like hydrogen and optimized gas ratios to prevent nodule defects and enhance fin coverage, thereby improving contact resistance and reducing capacitance effects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If standard epitaxial growth process is used, then source/drain regions are formed, but adjacent regions merge causing non-merging issues or shorts

Engineering Contradiction:

Improvesource/drain region separationVSAvoiddevice performance

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent modifies the epitaxial growth parameters by using a carrier gas mixture containing hydrogen (at least 5%, preferably at least 10%) instead of standard inert gases. This parameter change in gas composition alters the growth kinetics to produce rounded top profiles that prevent merging while maintaining proper separation between adjacent source/drain regions.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates a localized rounded top profile geometry at the epitaxial source/drain regions through controlled gas flow and composition. This local geometric modification at the region tops provides mechanical separation and prevents merging without affecting the overall structure or requiring changes to other parts of the device.

Inventive Principle:

Principle #3Local quality

2Productivity

If epitaxial growth rate is increased to improve throughput, then production efficiency increases, but merging issues worsen

Engineering Contradiction:

Improveproduction throughputVSAvoidsource/drain region separation

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent changes the epitaxial growth parameters by introducing hydrogen-containing carrier gas and optimizing gas flow rates. This enables faster growth rates while the hydrogen influences the growth morphology to maintain rounded tops that prevent merging, thus decoupling throughput improvement from precision degradation.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The rounded top profile is formed during the epitaxial growth process itself through preliminary control of gas composition and flow. This preliminary geometric configuration prevents merging issues before they can occur during subsequent processing steps, allowing higher growth rates without sacrificing separation precision.

Inventive Principle:

Principle #10Preliminary action

3Loss of time

If gas flow rate is increased to reduce processing time, then cycle time decreases, but merging control deteriorates

Engineering Contradiction:

Improveepitaxial growth cycle timeVSAvoidrounded top profile formation

Core Design Contradiction:

Loss of timeVSManufacturing precision

Solution Approach 1:

The patent optimizes the gas flow rate parameter within a specific range (2-10 L/min) and combines it with hydrogen-containing carrier gas composition. This parameter optimization enables faster processing while the hydrogen ensures proper rounded top profile formation, preventing the deterioration of precision that would normally accompany increased flow rates.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention uses a composite gas mixture combining carrier gas (such as nitrogen or argon) with hydrogen in specific proportions. This composite gas composition provides both the flow characteristics needed for efficient processing and the chemical properties necessary for forming rounded top profiles that maintain precision at higher speeds.

Inventive Principle:

Principle #40Composite materials

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 epitaxial scheme reduces nodule defects, prevents merging of neighboring source/drain regions, and enhances contact resistance, leading to improved device performance and a 20% increase in production throughput by allowing higher epitaxial growth rates and reduced transition times.

Implementation Method 1

epitaxially growing a source/drain region in the recess

Methodology Applied

Scientific EffectEpitaxy: Epitaxy

Data Source

PatentUS20230378176A1Source/Drain Regions of Semiconductor Devices and Methods of Forming the Same

Publication Date: 2023.11.23 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A semiconductor device includes: a first fin and a second fin extending from a substrate and an epitaxial source/drain region. The epitaxial source/drain region includes a first portion grown on the first fin and a second portion grown on the second fin, and the first portion and the second portion are joined at a merging boundary. The epitaxial source/drain region further includes a first subregion extending from a location level with a highest point of the epitaxial source/drain region to a location level with a highest point of the merging boundary, a second subregion extending from the location level with the highest point of the merging boundary to a location level with a lowest point of the merging boundary, and a third subregion extending from the location level with the lowest point of the merging boundary to a location level with a top surface of an ST