Glass Interposer Air-Gap Traces for Low-Crosstalk Bridge Routing

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Solution Overview

Problem

High-density electrical routing in bridge architectures faces limitations due to poor electrical performance, particularly with capacitance and crosstalk issues as line widths and spacings approach 2 μm/2 μm or smaller, even with the use of low-k or ultra-low-k dielectrics, which also pose mechanical reliability and cost concerns.

Innovation Solution

The implementation of glass interposers with high-density traces surrounded by air-gaps, where trenches are formed adjacent to the traces and a dielectric adhesive is used to attach a second glass substrate without vacuum, creating an air-gap that improves electrical performance by utilizing air's low dielectric constant.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If low-k or ultra-low-k dielectric materials are used to reduce capacitance and crosstalk, then electrical performance is improved, but system cost increases

Engineering Contradiction:

Improveelectrical performanceVSAvoidsystem cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces expensive low-k or ultra-low-k dielectric materials with air, which is a free and readily available substance. This substitution dramatically reduces material costs while maintaining or improving electrical performance, as air provides even better dielectric properties than the engineered low-k materials.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Speed

If high density L/S values are used in bridge architectures to provide necessary bandwidth, then data transmission capability is improved, but electrical performance deteriorates due to capacitance and crosstalk

Engineering Contradiction:

ImprovebandwidthVSAvoidelectrical performance

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent applies local quality by creating air-gaps specifically in the regions adjacent to conductive traces where capacitance and crosstalk occur, while maintaining the high density trace layout for bandwidth. The air-gap is localized to the trench regions surrounding each trace, providing improved electrical performance exactly where needed without altering the overall high-density interconnect architecture.

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

This solution significantly improves capacitance by approximately 50% and crosstalk by approximately 10% compared to traditional low-k materials, while maintaining mechanical reliability and reducing costs.

Implementation Method 1

air's low dielectric constant

Methodology Applied

Scientific EffectDielectric constant: Dielectric Permittivity

Data Source

PatentUS20240339381A1Air-gap traces and air-gap embedded bridge integrated in glass interposer

Publication Date: 2024.10.10 INTEL CORP

AI summary

Embodiments disclosed herein include an interposer. In an embodiment, the interposer comprises a substrate, where the substrate comprises a glass layer. In an embodiment, a trace is on the substrate, where the trace has a bottom surface, sidewall surfaces, and a top surface. In an embodiment, the sidewall surfaces and the top surface are exposed to air. In an embodiment, a trench into the substrate is adjacent to at least one sidewall surface of the trace.