Nanosheet FET Contact Trench Structure for Stable Resistance

Solution Overview

Problem

As semiconductor devices scale to smaller dimensions, nanosheet FET devices face challenges in maintaining consistent contact resistance due to variations in source/drain region thickness, leading to increased resistance and reduced performance.

Innovation Solution

The formation of trenches in the source/drain regions filled with metal-based contact material ensures uniform thickness and repeatable contact resistance by containing the source/drain contact material within these trenches, regardless of overfill or underfill conditions during epitaxial growth.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If source/drain contact material is deposited without trenches, then the fabrication process is simpler, but contact resistance varies due to thickness variations in source/drain regions

Engineering Contradiction:

Improvecontact resistance consistencyVSAvoidfabrication process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The source/drain region is segmented by forming trenches that divide it into discrete contact areas. This segmentation ensures that contact material is deposited in controlled, isolated regions, eliminating variability caused by overall thickness fluctuations in the source/drain layer and achieving consistent contact resistance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Trenches are formed in the source/drain region before contact material deposition. This preliminary action creates predetermined contact sites with controlled geometry, ensuring that subsequent contact material deposition occurs in well-defined regions regardless of source/drain layer thickness variations.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If trenches are formed and filled with contact material, then contact resistance variability is reduced, but the fabrication process becomes more complex

Engineering Contradiction:

Improvedevice performance consistencyVSAvoidfabrication ease

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The source/drain region is segmented by forming trenches that divide it into discrete contact areas. This segmentation ensures that contact material is deposited in controlled, isolated regions, eliminating variability caused by overall thickness fluctuations in the source/drain layer and achieving consistent contact resistance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The physical state and geometry of the contact region are changed by forming trenches with specific dimensions and profiles. This parameter change transforms the contact interface from a planar surface subject to thickness variations into a controlled three-dimensional structure with defined contact area, improving reliability.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If epitaxial growth is performed without trench containment, then source/drain region thickness varies, but the growth process is faster and simpler

Engineering Contradiction:

Improvesource/drain region uniformityVSAvoidepitaxial growth efficiency

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

Trenches are formed in the source/drain region before contact material deposition. This preliminary action creates predetermined contact sites with controlled geometry, ensuring that subsequent contact material deposition occurs in well-defined regions regardless of source/drain layer thickness variations.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The trench structure creates local quality differences in the source/drain region, with contact areas having controlled geometry and non-contact areas maintaining their original characteristics. This local differentiation ensures consistent contact properties without requiring uniformity across the entire source/drain region, maintaining growth efficiency.

Inventive Principle:

Principle #3Local quality

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 reduces contact resistance variability and enhances the performance of nanosheet FET devices by maintaining consistent contact area and resistance across different growth conditions, improving device reliability and efficiency.

Implementation Method 1

the trenches are filled with a metal-based material

Methodology Applied

Scientific EffectPhysical Vapour Deposition: Physical Vapour Deposition

Implementation Method 2

A trench is etched in the source/drain region through at least a portion of the sacrificial layer

Methodology Applied

Scientific EffectEtching:

Data Source

PatentUS11894423B2Contact resistance reduction in nanosheet device structure

Publication Date: 2024.02.06 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

Techniques are provided to fabricate semiconductor devices having a nanosheet field-effect transistor device disposed on a semiconductor substrate. The nanosheet field-effect transistor device includes a nanosheet stack structure including a semiconductor channel layer and a source/drain region in contact with an end portion of the semiconductor channel layer of the nanosheet stack structure. A trench formed in the source/drain region is filled with a metal-based material. The metal-based material filling the trench in the source/drain region mitigates the effect of source/drain material overfill on the contact resistance of the semiconductor device.