GAA Gate Conductor Layout for Stable Threshold Voltage

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Solution Overview

Problem

As transistor devices scale to smaller sizes, thinner work function metal layers face challenges in shielding the channel from the influence of overlying metals of different polarity, affecting voltage threshold efficacy.

Innovation Solution

A barrier layer is used to protect the first work function metal while etching away the second metal, followed by depositing a second work function metal in the second device region, ensuring the first metal is not masked by the second, thus maintaining voltage threshold effectiveness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If thinner work function metal layers are used to scale transistor devices, then device size is reduced, but the ability to shield the channel from overlying metals of different polarity deteriorates

Engineering Contradiction:

Improvetransistor sizeVSAvoidvoltage threshold efficacy

Core Design Contradiction:

Length of moving objectVSReliability

Solution Approach 1:

The gate stack is segmented into distinct work function metal layers (first and second work function metals) with different polarities, separated by a barrier layer. This segmentation allows each layer to independently control the voltage threshold for its respective transistor type without interference from the other polarity metal, resolving the shielding problem while maintaining thin overall dimensions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A barrier layer is introduced as an intermediary between the first and second work function metals. This barrier layer prevents direct interaction and electrical influence between metals of different polarity, allowing thin work function metal layers to effectively control their respective channels without being overwhelmed by overlying metals of opposite polarity.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If different work function metals are layered to form gate contacts for pFETs and nFETs, then voltage threshold tuning is achieved, but the overlying metal influences the underlying metal, affecting voltage threshold control

Engineering Contradiction:

Improvevoltage threshold tuningVSAvoidvoltage threshold control

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

Different work function metals are placed in different local regions (first work function metal for pFETs, second work function metal for nFETs) with a barrier layer preventing cross-influence. This local quality approach allows each metal to independently establish the voltage threshold for its specific transistor type without being affected by the other polarity metal, maintaining precise voltage threshold control while achieving versatility.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS12471355B2Non-overlapping gate conductors for GAA transistors

Publication Date: 2025.11.11 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

Semiconductor devices and methods of forming the same include a first transistor in a first region having a first work function metal layer. A second transistor in a second region has a second work function metal layer that overlaps a portion of the first work function metal layer and that has a vertical part above the portion of the first work function metal layer.