FinFET Work Function Layer Layout to Reduce Voltage Instability

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Solution Overview

Problem

As semiconductor technology advances and feature sizes decrease, the resistance of metal gate electrodes becomes critical, but the presence of contact metal between fin structures can induce triggered voltage instability, reducing device performance.

Innovation Solution

The semiconductor structure is formed using a replacement polysilicon gate (RPG) or gate-last process, where the contact metal is positioned such that its bottom surface is higher than the top surface of the fin structures, and it is not between the fin structures, thereby mitigating triggered voltage instability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If contact metal is positioned between fin structures, then electrical connection is achieved, but triggered voltage instability occurs reducing device performance

Engineering Contradiction:

Improvedevice performanceVSAvoidtriggered voltage instability

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The contact metal is repositioned from a horizontal placement between fins to a vertical placement above the fin structures, changing the spatial dimension of contact metal-fin interaction. This dimensional shift eliminates the harmful voltage instability while preserving electrical connectivity through the gate structure.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The gate structure serves as an intermediary element between the contact metal and the fin structures. Instead of direct contact between metal and fins, the gate acts as a mediator that transmits electrical connection while preventing the direct interaction that causes triggered voltage instability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Length of moving object

If metal gate electrode dimensions are decreased, then device scaling is achieved, but resistance of metal gate electrode becomes critical

Engineering Contradiction:

Improvefeature sizeVSAvoidmetal gate electrode resistance

Core Design Contradiction:

Length of moving objectVSReliability

Solution Approach 1:

The gate structure employs composite material construction with metal gate electrodes combined with dielectric materials. This composite approach allows scaling to smaller dimensions while maintaining optimized resistance characteristics through material property selection and structural design.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention optimizes resistance by changing physical parameters of the metal gate electrode including material composition, thickness, and dimensional proportions. These parameter adjustments enable successful device scaling while keeping resistance within acceptable limits.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12170332B2Fin field effect transistor devices including NMOS device and PMOS device with varied geometry of work function layers

Publication Date: 2024.12.17 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A semiconductor structure includes a first device and a second device. The first device includes a plurality of first fins, a first work function layer over the plurality of first fins, and a first contact layer over the first work function layer. The second device includes a plurality of second fins, a second work function layer and the first work function layer over the plurality of the second fins, and a second contact layer over the first work function layer and the second work function layer. A distance between a bottom surface of the first work function layer and a bottom surface of the first contact layer is greater than a distance between a side surface of the first work function layer of the first device and a side surface of the first contact layer.