GAA Nanosheet Channel Orientation for Balanced Carrier Mobility

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Solution Overview

Problem

The semiconductor industry faces a challenge in achieving balanced hole and electron mobility as feature sizes reduce, leading to trade-offs in device performance due to factors like surface roughness scattering, remote phonon scattering, and remote coulomb scattering, particularly affecting (110)/ channels.

Innovation Solution

Utilizing a (551)/ substrate orientation tilted 8 degrees from (110) with a silicon surface for nanosheet channels, combined with surface roughness treatment, to maintain high hole mobility and prevent electron mobility loss during scaling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If minimum feature size is reduced to increase integration density, then more components can be integrated into a given chip area, but a trade-off between hole and electron mobility in the channel regions occurs which affects device performance

Engineering Contradiction:

Improveintegration densityVSAvoiddevice performance

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies different crystallographic orientations to different regions of the channel structure. Specifically, it uses (100)-oriented silicon for electron transport channels and (110)-oriented silicon for hole transport channels, allowing each region to have optimized local properties for its specific carrier type while maintaining overall device functionality at scaled dimensions

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent introduces asymmetric channel structures with different orientations for electron and hole transport. The channel region is divided into asymmetric segments with distinct crystallographic orientations, enabling independent optimization of electron and hole mobility pathways rather than using a uniform symmetric structure

Inventive Principle:

Principle #4Asymmetry

2Length of moving object

If channel height is reduced to enable further scaling, then integration density increases, but surface roughness scattering and other scattering mechanisms worsen which affects carrier mobility

Engineering Contradiction:

Improvechannel heightVSAvoidcarrier mobility

Core Design Contradiction:

Length of moving objectVSReliability

Solution Approach 1:

The patent changes the crystallographic orientation parameter of the channel regions from conventional uniform orientations to a combination of (100) and (110) orientations. This parameter change fundamentally alters the scattering mechanisms and carrier transport properties, enabling maintained mobility even at reduced channel heights by optimizing the band structure and surface properties for each carrier type

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20260026059A1Semiconductor devices and methods for fabrication thereof

Publication Date: 2026.01.22 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

Embodiments of the present disclosure provide a GAA device fabricated from a substrate having a (551)<110> top surface. Selecting the (551)/<110> substrate enables channel height scaling with improved hole mobility and without sacrificing electron mobility.