Metal Gate Oxide Layer for FinFET Etch Protection

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Solution Overview

Problem

In semiconductor IC fabrication, particularly in FinFET gate-last processes, metal patterning processes often damage metal barrier layers, causing metal intrusion into the gate dielectric layer and device defects due to poor etch selectivity of conventional etchants like SC-1 and SC-2.

Innovation Solution

A method involving the formation of a barrier layer over the gate dielectric layer, followed by an oxide layer that protects the barrier layer from etching during metal patterning, using an oxide layer formed through oxygen treatment or deposition, which prevents contamination and maintains the barrier layer's protective capability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional etchants (SC-1, SC-2) are used for metal patterning, then the metal patterning process can be completed, but the metal barrier layer is damaged and metal intrudes into the gate dielectric layer causing device defects

Engineering Contradiction:

Improvemetal patterning process completionVSAvoiddevice defect rate

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

An oxide layer is introduced as an intermediary protective layer between the metal barrier layer and the etchant during metal patterning processes. This oxide layer acts as a mediator that allows the etchant to remove metal while preventing the etchant from damaging the metal barrier layer, thus avoiding metal intrusion into the gate dielectric layer.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The oxide layer is formed in advance before the metal patterning process to provide pre-protection to the metal barrier layer. This preliminary action ensures that when the etchant is applied later, the protective barrier is already in place, preventing metal barrier layer damage and subsequent device defects.

Inventive Principle:

Principle #10Preliminary action

2Device complexity

If metal patterning processes are performed to form the metal gate electrode, then the gate electrode structure is created, but the metal barrier layer is damaged due to poor etch selectivity

Engineering Contradiction:

Improvegate electrode structure formationVSAvoidmetal barrier layer integrity

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The oxide layer serves as a protective intermediary that enables the metal patterning process to proceed with high precision. It allows selective metal removal while maintaining the integrity of the metal barrier layer, thus achieving both complex gate electrode formation and precise manufacturing control.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The oxide layer provides beforehand cushioning protection to the metal barrier layer against the harsh etchant environment. This protective cushioning ensures that the metal barrier layer maintains its integrity even during aggressive metal patterning processes required for complex gate electrode structures.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Ease of manufacture

If the metal barrier layer is exposed during metal patterning, then metal can be patterned, but metal intrudes into the gate dielectric layer causing contamination

Engineering Contradiction:

Improvemetal patterning feasibilityVSAvoidmetal contamination of gate dielectric

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The oxide layer acts as a protective intermediary that allows metal patterning to be performed easily while simultaneously preventing metal contamination of the gate dielectric layer. It mediates between the need for metal removal and the need to protect the underlying dielectric structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The oxide layer is formed in advance to provide pre-protection against metal contamination. This preliminary protective action ensures that when metal patterning is performed, the gate dielectric layer is already shielded from metal intrusion, maintaining manufacturing feasibility while preventing harmful contamination.

Inventive Principle:

Principle #10Preliminary action

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 solution effectively prevents metal contamination of the gate dielectric layer, reducing device defects and ensuring the integrity of the barrier layer's protective function during metal patterning processes, suitable for integration into existing FinFET fabrication flows for advanced process nodes like 16 nm and beyond.

Implementation Method 1

forming an oxide layer over the barrier layer... The oxide layer stops various etchants used in the metal patterning process from reaching the barrier layer

Methodology Applied

Scientific EffectEtch resistance:

Implementation Method 2

metal barrier layers provided between the metal gate electrode and a gate dielectric layer... prevents metal contamination of the gate dielectric layer

Methodology Applied

Scientific EffectDiffusion barrier: Diffusion Barrier

Data Source

PatentUS9761684B2Method and structure for metal gates

Publication Date: 2017.09.12 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A semiconductor device having metal gates and methods of forming the same are disclosed. The semiconductor device includes a substrate and a gate structure over the substrate. The gate structure includes a gate dielectric layer over the substrate, a barrier layer over the gate dielectric layer, an oxide layer over the barrier layer, and a work function metal layer over the oxide layer.