Dummy Fill with Self-Canceling Eddy Currents for Inductor Q-Factor

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Solution Overview

Problem

Conventional dummy fill elements in inductors allow eddy currents to flow, impacting the quality factor (Q-factor) of inductors at high frequencies, thereby affecting the performance of integrated circuits (ICs) due to parasitic capacitance and planarization challenges during metal layer processing.

Innovation Solution

A dummy fill element with a first and second conductive incomplete loop, where the ends of each loop are electrically connected, self-canceling eddy currents generated by the magnetic field, maintaining the inductor's Q-factor and allowing for desired metal fill density during planarization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If conventional dummy fill elements are used inside inductor metal turns, then metal pattern density is improved for planarization, but eddy currents are generated that degrade inductor Q-factor at high frequencies

Engineering Contradiction:

Improvemetal pattern densityVSAvoidinductor Q-factor

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The dummy fill element is segmented into multiple incomplete conductive loops (first conductive incomplete loop and second conductive incomplete loop) instead of using a solid conventional shape. These segmented loops provide sufficient metal pattern density for planarization while disrupting continuous eddy current paths, thereby maintaining inductor Q-factor at high frequencies.

Inventive Principle:

Principle #1Segmentation

2Ease of manufacture

If dummy fill elements with simple cross-sectional shapes are used, then manufacturing is simplified, but eddy currents flow in closed circular paths within the conductors

Engineering Contradiction:

Improvedummy fill element fabricationVSAvoideddy currents

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

Instead of using conventional closed-loop dummy fill shapes that facilitate eddy current flow, the invention inverts the approach by using open-ended incomplete conductive loops. This inversion disrupts the closed circular paths necessary for eddy currents while maintaining manufacturability through simple geometric patterns that can be fabricated using standard processes.

Inventive Principle:

Principle #13The other way round (Inversion)

3Manufacturing precision

If the open center of metal turns is filled with conventional dummy elements, then planarization damage is prevented, but the Q-factor of the inductor is impacted at high frequencies

Engineering Contradiction:

Improveplanarization qualityVSAvoidinductor performance

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The dummy fill element is designed with locally differentiated properties: the incomplete conductive loops are positioned and shaped to provide metal pattern density specifically where needed for planarization support, while their open-ended structure locally prevents eddy current formation. This local quality differentiation allows simultaneous achievement of planarization quality and inductor performance.

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

The self-canceling eddy current dummy fill element effectively reduces eddy current impacts on the inductor's Q-factor, maintaining performance while ensuring proper planarization and metal density, unlike conventional dummy fill elements.

Implementation Method 1

A dummy fill element with a first and second conductive incomplete loop, where the ends of each loop are electrically connected, self-canceling eddy currents generated by the magnetic field

Methodology Applied

Scientific EffectEddy current self-canceling: Eddy Currents

Implementation Method 2

Eddy currents are circular or looping electrical currents induced within conductors by a changing magnetic field in the conductor based on Faraday's law of induction

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS11011303B2Dummy fill with eddy current self-canceling element for inductor component

Publication Date: 2021.05.18 GLOBALFOUNDRIES US INC

AI summary

A dummy fill element for positioning inside an active inductor component of an integrated circuit (IC), the inductor component, the IC and a related method, are disclosed. The active inductor component is configured to convert electrical energy into magnetic energy to reduce parasitic capacitance in an IC. The dummy fill element includes: a first conductive incomplete loop having a first end and a second end, and a second conductive incomplete loop having a first end and a second end. First ends of the first and second conductive incomplete loops are electrically connected, and the second ends of the first and second conductive incomplete loops are electrically connected. In this manner, eddy currents created in each conductive incomplete loop by the magnetic energy cancel at least a portion of each other, allowing for a desired metal fill density and maintaining the inductor's Q-factor.