Air Spacer Protection Ring for Barrier Layer Oxidation Control

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Solution Overview

Problem

Conventional methods for forming air spacers in low-k dielectric layers result in oxidation and damage to the bottom portions of barrier layers due to exposure during the removal of sacrificial layers, leading to increased resistance and degradation of circuit performance.

Innovation Solution

A method involving the deposition of a sacrificial spacer followed by anisotropic etching to form a sacrificial ring, then depositing a protection layer and etching its horizontal portions to create a protection ring that contacts the underlying feature, preventing oxidation of the barrier layer bottom portions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the sacrificial layer is removed to form air spacers, then parasitic capacitance is reduced, but the barrier layer bottom portions are exposed to oxidation and damage

Engineering Contradiction:

Improveparasitic capacitanceVSAvoidbarrier layer integrity

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

A protection layer is deposited over the barrier layer before the sacrificial layer is removed. This preliminary protective measure ensures that when the sacrificial layer is subsequently removed to form air spacers, the barrier layer bottom portions are already protected from oxidation and damage, thus resolving the contradiction between reducing parasitic capacitance and maintaining barrier layer integrity

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The protection layer acts as an intermediary between the barrier layer and the oxidizing environment. It is deposited conformally over the barrier layer and extends into the air spacer region, providing a protective barrier that prevents direct contact between oxygen and the barrier layer bottom portions while still allowing the air spacer to form and reduce parasitic capacitance

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the protection layer is deposited before removing the sacrificial layer, then the barrier layer is protected from oxidation, but the process complexity increases

Engineering Contradiction:

Improvebarrier layer protectionVSAvoidprocess steps

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The protection layer deposition is merged with the existing process flow by depositing it conformally over the barrier layer in the same sequence as the sacrificial layer removal process. This integration adds only one deposition step while achieving comprehensive protection, thus minimizing the increase in process complexity

Inventive Principle:

Principle #5Merging (Combining)

3Reliability

If the protection layer extends into the air spacer region, then complete coverage of the barrier layer is achieved, but material consumption increases

Engineering Contradiction:

Improveprotection layer coverageVSAvoidprotection layer material

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The protection layer is deposited conformally, which means it locally adapts to the underlying structure. It extends into the air spacer region only where the barrier layer exists and needs protection, rather than uniformly covering the entire wafer surface. This localized deposition achieves complete coverage of the barrier layer bottom portions while minimizing unnecessary material consumption in regions where protection is not needed

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

Prevents oxidation of the barrier layer bottom portions, reducing parasitic capacitance and maintaining circuit performance by ensuring the protection ring fully covers the barrier layer, thus enhancing the integrity and efficiency of the conductive features.

Implementation Method 1

performing a first anisotropic etching process to etch the sacrificial spacer layer, wherein a first bottom portion of the sacrificial spacer layer at a bottom of the opening is removed to reveal the first conductive feature, and a first vertical portion of the sacrificial spacer layer in the opening and on a sidewall of the dielectric layer is left to form a sacrificial ring

Methodology Applied

Scientific EffectAnisotropic etching:

Implementation Method 2

depositing a sacrificial spacer layer extending into the opening; depositing a protection layer extending into the opening and on the sacrificial ring

Methodology Applied

Scientific EffectDeposition: Deposition (physical)

Data Source

PatentUS20250329582A1Reducing oxidation by etching sacrificial and protection layer separately

Publication Date: 2025.10.23 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A structure includes a first conductive feature, a first etch stop layer over the first conductive feature, a dielectric layer over the first etch stop layer, and a second conductive feature in the dielectric layer and the first etch stop layer. The second conductive feature is over and contacting the first conductive feature. An air spacer encircles the second conductive feature, and sidewalls of the second conductive feature are exposed to the air spacer. A protection ring further encircles the second conductive feature, and the protection ring fully separates the second conductive feature from the air spacer.