Air Gap Formation in Inter-Metal Dielectric for 10 nm Contact Resistance

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Solution Overview

Problem

As semiconductor industry scales down to 10 nm node generation, contact area of contact plugs decreases significantly, leading to increased resistance and damaged regions in adjacent dielectric layers during contact hole formation, affecting device operation.

Innovation Solution

A method involving forming an inter-metal dielectric layer, creating trenches, transforming part of the layer into a damaged layer, forming a protective layer, and removing the damaged layer to create an air gap adjacent to the protective layer, with a metal interconnection below the air gap.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of moving object

If contact plug size is reduced to scale down to 10 nm node generation, then device integration density is improved, but contact resistance increases significantly

Engineering Contradiction:

Improvecontact areaVSAvoidcontact resistance

Core Design Contradiction:

Area of moving objectVSReliability

Solution Approach 1:

An air gap is introduced as an intermediary structure between the contact plug and the inter-metal dielectric layer. This air gap serves as a mediator that reduces the effective contact area between the conductive layers, thereby lowering contact resistance while maintaining the small physical footprint required for 10 nm node scaling

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The contact resistance is reduced by changing the physical and electrical parameters of the contact structure. Specifically, the air gap modifies the effective contact area and electrical field distribution, transforming the contact interface properties to achieve lower resistance despite reduced contact plug dimensions

Inventive Principle:

Principle #35Parameter changes

2Area of moving object

If contact holes are formed to reduce contact plug size, then device integration density is improved, but damaged regions are created in adjacent dielectric layer

Engineering Contradiction:

Improvecontact plug areaVSAvoiddamaged regions in dielectric layer

Core Design Contradiction:

Area of moving objectVSObject-generated harmful factors

Solution Approach 1:

The damaged layer, which is an unwanted byproduct of contact hole formation, is selectively removed through a selective etching process. The etchant targets and extracts only the damaged dielectric material while leaving the healthy dielectric and other structures intact, thereby eliminating the harmful damaged regions without affecting the overall device structure

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The damaged layer created during contact hole formation is converted from a harmful defect into a useful feature. By selectively removing only the damaged portions, the process creates air gaps that serve beneficial functions: reducing contact resistance and preventing stress-induced device failures. The harmful damaged material becomes the precursor to a protective and performance-enhancing structure

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS10204826B1Method for removing damaged layer embedded in a dielectric layer

Publication Date: 2019.02.12 UNITED MICROELECTRONICS CORP

AI summary

A method for fabricating semiconductor device includes the steps of: forming an inter-metal dielectric (IMD) layer on a substrate; forming a trench in the IMD layer; performing a treatment process to transform part of the IMD layer into a damaged layer adjacent to the trench; forming a protective layer on a sidewall of the damaged layer; forming a metal layer in the trench; and removing the damaged layer to form an air gap adjacent to the protective layer.