BEOL Isolation Elements With Etch-Resistant Caps for Low Capacitance

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Solution Overview

Problem

In advanced back-end-of-line (BEOL) interconnects, adjacent metal lines experience time-dependent dielectric breakdown (TDBB) and high capacitance due to close proximity, leading to RC delay issues.

Innovation Solution

The use of isolation elements with a dielectric lower portion and an etching-resistant upper portion made of a polymer with specific properties to prevent damage during etching processes, maintaining separation and reducing capacitance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If metal lines are positioned close to each other to increase integration density, then area utilization is improved, but time-dependent dielectric breakdown (TDBB) deteriorates and capacitance increases

Engineering Contradiction:

Improvearea utilizationVSAvoidtime-dependent dielectric breakdown

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The isolation element is segmented into two distinct portions: a lower portion made of dielectric material and an upper portion made of etching-resistant material. This segmentation allows each portion to perform its specific function - the lower portion provides electrical isolation while the upper portion protects against etching damage during subsequent processing steps, thereby maintaining reliability even when metal lines are closely spaced

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different materials are used at different locations of the isolation element to address local requirements. The lower portion uses dielectric material for electrical isolation where metal lines are present, while the upper portion uses etching-resistant material where protection from subsequent etching processes is needed. This local differentiation resolves the TDBB issue by ensuring proper isolation at the critical interface with metal lines

Inventive Principle:

Principle #3Local quality

2Area of stationary object

If metal lines are positioned close to each other to increase integration density, then area utilization is improved, but capacitance between adjacent lines increases

Engineering Contradiction:

Improvearea utilizationVSAvoidcapacitance

Core Design Contradiction:

Area of stationary objectVSObject-generated harmful factors

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The isolation element is formed as a composite structure combining dielectric material and etching-resistant material. This composite structure provides both the electrical isolation properties of the dielectric material and the protective properties of the etching-resistant material, enabling close metal line spacing with reduced capacitance while maintaining process compatibility

Inventive Principle:

Principle #40Composite materials

3Manufacturing precision

If etching process is used to form upper interconnect level to improve manufacturing precision, then patterning accuracy is improved, but isolation elements are damaged and voids are formed

Engineering Contradiction:

Improvepatterning accuracyVSAvoidisolation element integrity

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The etching-resistant upper portion is formed in advance before the etching process that forms the upper interconnect level. This preliminary protective layer prevents the etching process from damaging the isolation elements or forming voids, while still allowing the etching process to achieve the required patterning accuracy for the upper interconnect level

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The etching-resistant upper portion acts as an intermediary protective layer between the etching process and the isolation elements. It absorbs the harmful effects of the etching process, preventing direct contact with the isolation elements, thereby maintaining both patterning accuracy and isolation element integrity

Inventive Principle:

Principle #24Intermediary (Mediator)

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 tiger tooth defects and deterioration of TDBB, while keeping capacitance low, thereby improving semiconductor structure performance.

Implementation Method 1

The etching-resistant material exhibits a comparatively higher resistivity to an etching process than the dielectric material, such that the upper portion is capable of resisting the etching process

Methodology Applied

Scientific EffectEtching resistance:

Data Source

PatentUS20260018459A1Semiconductor structure including isolation elements with etching-resistant upper portions and method for manufacturing the same

Publication Date: 2026.01.15 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A method for manufacturing a semiconductor structure includes: forming first conducting portions that are spaced apart from each other on a base structure; forming isolation elements, each of which includes a dielectric lower portion and an etching-resistant upper portion covering the dielectric lower portion, the etching-resistant upper portion being made of an etching-resistant material different from a dielectric material of the dielectric lower portion, each of the isolation elements being isolated and exposed from two adjacent ones of the first conducting portions; sequentially forming an etch stop layer and an interlayer dielectric over the first conducting portions and the isolation elements; forming a cavity which extends through the etch stop layer and the interlayer dielectric, and which exposes one of the first conducting portions; and filling the cavity with a second conducting portion.