Optical Modulator Heater Tuning With AC Drive Against Electromigration

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Optical modulators face reliability issues due to electromigration (EM) caused by heat generated from large currents, leading to hillocks and voids that can result in short or open circuits.

Innovation Solution

Employing a heater driven by alternating current (AC) signals to thermally adjust the resonant wavelength, which reduces electromigration by alternating the direction of current flow and lowers current density, maintaining thermal efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a heater is driven by large current to thermally adjust the resonant wavelength, then the thermal efficiency is improved, but electromigration occurs degrading reliability

Engineering Contradiction:

Improvethermal efficiencyVSAvoidheater reliability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent applies periodic action by driving the heater with alternating current (AC) signals that periodically reverse direction. This periodic current flow prevents electromigration by ensuring that metal atoms are subjected to equal and opposite electrical stresses over time, causing them to remain stationary on average. The AC signal maintains thermal efficiency through continuous current flow while eliminating the unidirectional electromigration damage that would occur with DC or large pulsed currents.

Inventive Principle:

Principle #19Periodic action

2Power

If large current is used to drive the heater, then thermal adjustment capability is improved, but electromigration causes hillocks and voids leading to short or open circuits

Engineering Contradiction:

Improveheater powerVSAvoidheater reliability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent uses periodic action through AC signal driving to maintain high heater power while preventing electromigration. The alternating current direction ensures that any metal atom displacement caused by electrical stress is reversed in subsequent cycles, preventing the accumulation of hillocks and voids that would lead to circuit failures.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent applies parameter changes by transitioning from DC or pulsed current to AC current with specific frequency and amplitude characteristics. This parameter change allows the heater to operate at high power levels while the AC nature of the current prevents electromigration, as the alternating electrical stress prevents permanent metal atom displacement.

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If unidirectional current flow is used, then thermal heating is efficient, but electromigration impels metal atoms in one direction causing non-uniformity

Engineering Contradiction:

Improveheating efficiencyVSAvoidconductive segment uniformity

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

The patent applies periodic action by using AC current that periodically reverses direction. This ensures that metal atoms experience equal and opposite electrical stresses in alternating cycles, preventing net displacement and maintaining uniform composition throughout the conductive segment while still providing efficient thermal heating through continuous current flow.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent inverts the conventional unidirectional current approach by using bidirectional AC current. This inversion causes metal atoms to be subjected to reversing electrical stresses that counterbalance each other, preventing the one-way electromigration that would otherwise cause non-uniformity and material degradation.

Inventive Principle:

Principle #13The other way round (Inversion)

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 electromigration and enhances the reliability of the heater while maintaining thermal efficiency, ensuring consistent operation of the optical modulator.

Implementation Method 1

the heater may generate heat induced by large current

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

the heater may generate heat induced by large current, which may induce electromigration (EM) issues degrading reliability of the heater

Methodology Applied

Scientific EffectElectromigration:

Data Source

PatentUS12523894B2Semiconductor device, photonic circuit, and method for adjusting resonant wavelength of optical modulator

Publication Date: 2026.01.13 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

The present disclosure provides a semiconductor device, a photonic circuit, and a method for adjusting a resonant wavelength of an optical modulator. The semiconductor device includes a substrate, a first waveguide disposed on the substrate, a second waveguide disposed on the substrate and spaced apart from the first waveguide by a first distance, and a heater disposed on the second waveguide and having a first terminal and a second terminal. In addition, the first terminal of the heater is configured to receive a first electrical signal; the second terminal of the heater is configured to receive a second electrical signal; and the heater is configured to carry a time-varying current in response to the first electrical signal and the second electrical signal.