Partial Metal Fill Layout to Prevent ELK Dielectric Delamination

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Solution Overview

Problem

The delamination of ultra-thick metal (UTM) conductors from extreme-low-k dielectric layers is a significant challenge due to the poor mechanical strength of these dielectric materials, which compromises the quality factor of RF filters and related circuits.

Innovation Solution

A partial metal fill arrangement is implemented within the footprint of the UTM inductor, featuring interrupted via stacks that do not extend through all the metal layers, thereby inhibiting electrical coupling and enhancing mechanical strength. Outside the footprint, uninterrupted via stacks extend through all metal layers to further strengthen the dielectric layer without significantly affecting the quality factor.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If dummy metal fill is used outside the UTM footprint to strengthen the dielectric layer, then delamination is prevented, but the quality factor decreases due to electrical coupling of the metal fill to the UTM conductor

Engineering Contradiction:

Improvedielectric layer strengthVSAvoidquality factor

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The via stacks are segmented into two types: uninterrupted via stacks outside the UTM footprint that extend through all metal layers to provide mechanical strengthening, and interrupted via stacks within the footprint that do not extend through all metal layers to avoid electrical coupling. This segmentation allows the dielectric layer to be strengthened without degrading the quality factor.

Inventive Principle:

Principle #1Segmentation

2Reliability

If ELK dielectric materials are used to enhance electrical performance, then the dielectric constant is reduced, but mechanical strength deteriorates due to porosity

Engineering Contradiction:

Improveelectrical performanceVSAvoidmechanical strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent creates a composite structure within the dielectric layer by incorporating metal via stacks that extend through multiple metal layers. This composite arrangement of dielectric material and metal structures provides mechanical reinforcement to the porous ELK dielectric, improving its strength while maintaining the low dielectric constant property.

Inventive Principle:

Principle #40Composite materials

3Strength

If uninterrupted via stacks are used within the UTM footprint to strengthen the dielectric layer, then delamination is prevented, but electrical coupling with the UTM conductor increases, reducing the quality factor

Engineering Contradiction:

Improvedielectric layer strengthVSAvoidquality factor

Core Design Contradiction:

StrengthVSLoss of energy

Solution Approach 1:

The patent applies different via stack configurations to different locations: within the UTM footprint, interrupted via stacks are used that do not extend through all metal layers, providing localized mechanical support without creating electrical coupling. Outside the footprint, uninterrupted via stacks provide full mechanical strengthening. This local differentiation resolves the contradiction between strength enhancement and quality factor maintenance.

Inventive Principle:

Principle #3Local quality

Data Source

PatentEP3513430B1Partial metal fill for preventing extreme-low-k dielectric delamination

Publication Date: 2025.01.29 QUALCOMM INC

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AI summary

A partial metal fill is provided within the footprint of an ultra-thick-metal (UTM) conductor on a dielectric layer to strengthen the dielectric layer to inhibit delamination of the UTM conductor without inducing significant electrical coupling between the UTM conductor and the partial metal fill.