3D-Stacked PIC-EIC Structure With Cavities for Heater Thermal Isolation

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Solution Overview

Problem

Photonic integrated circuits (PICs) in optical transceivers are highly sensitive to temperature changes due to their thermo-optic coefficient, leading to significant energy consumption by integrated heaters, and conventional thermal design optimization is inadequate for efficient thermal isolation.

Innovation Solution

The integration of cavities between the PIC and the electronic integrated circuit (EIC) for improved thermal isolation, utilizing 3D stacking and substrate thinning to enhance thermal efficiency while maintaining electrical connectivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If conventional thermal design optimization is used, then heater energy consumption is reduced, but thermal isolation between PIC and EIC is insufficient

Engineering Contradiction:

Improveheater energy consumptionVSAvoidthermal isolation

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The bonding layer is segmented into multiple sections: a first bonding layer section between the heater and through-cut with lower thermal conductivity, and a second bonding layer section between the through-cut and EIC with higher thermal conductivity. This segmentation allows the bonding layer to simultaneously provide mechanical bonding strength and directional thermal management, isolating the heater thermally while maintaining structural integrity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A through-cut is introduced as an intermediary thermal barrier between the heater and the EIC. This through-cut extends through the bonding layer and acts as a thermal isolation structure, preventing direct heat transfer from the heater to the EIC while allowing the bonding layer to maintain mechanical connection between the PIC and EIC.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Use of energy by moving object

If substrate thinning is performed for optical coupling, then optical coupling between waveguide and interposer is enabled, but conventional substrate undercut cannot be used for thermal isolation

Engineering Contradiction:

Improveoptical coupling efficiencyVSAvoidthermal isolation capability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

Since substrate undercut in the vertical dimension is no longer feasible after substrate thinning, the thermal isolation strategy shifts to the lateral dimension. Through-cuts are introduced as lateral thermal barriers that extend through the bonding layer, providing thermal isolation without requiring substrate thickness. This dimensional shift allows thermal management to function effectively in thinned substrates.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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

Enhances thermal isolation of heaters, reducing energy consumption and improving the efficiency of photonic devices by limiting heat loss through the bonding layer and substrate.

Implementation Method 1

the one or more cavities are configured to reflect 20% to 80% of an entire amount of thermal energy flowing from the heater towards the EIC and/or from the EIC towards the waveguide

Methodology Applied

Scientific EffectThermal reflection: Reflection

Implementation Method 2

a heater configured to heat the waveguide

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS20260005091A1Thermally efficient integrated device

Publication Date: 2026.01.01 INTERUNIVERSITAIR MICRO ELECTRONICS CENT (IMEC VZW)

AI summary

Electronic-photonic systems including an integrated device, and methods for manufacturing the integrated device, are provided. In one aspect, the integrated device includes an electronic integrated circuit (EIC) and a photonic integrated circuit (PIC) bonded and electrically connected to the EIC. The PIC includes a waveguide and a heater configured to heat the waveguide. The integrated device includes one or more cavities arranged between the heater and the EIC for thermally isolating the heater from the EIC.