Integrated BAW Filter Structure for High-Frequency Substrates

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Solution Overview

Problem

The integration of bulk acoustic wave (BAW) filters with circuit substrates in semiconductor devices is still under development, particularly for high-frequency applications like 5G operations, where existing technologies face challenges in effectively combining BAW filters with circuit substrates such as silicon and GaN devices.

Innovation Solution

A structure and method for integrating a BAW filter with a circuit substrate, involving a first metal layer, buffer layer, absorbing layer, electrode layers, piezoelectric material units, protection layer, and interlayer dielectric layer, with features like air-gap regions and via connections, to enhance mechanical support and electrical connectivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If BAW filter is integrated with circuit substrate for high-frequency operation, then frequency performance is improved, but manufacturing complexity increases

Engineering Contradiction:

Improvefrequency operationVSAvoidintegration complexity

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The BAW filter structure is segmented into multiple functional layers including piezoelectric material units, buffer layers, absorbing layers, and electrode layers. Each layer performs a specific function and can be independently optimized, allowing high-frequency performance while managing manufacturing complexity through modular fabrication processes

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The BAW filter is nested within the circuit substrate structure, with the piezoelectric material units embedded between electrode layers, which are in turn integrated with the circuit substrate. This nested arrangement allows the filter to be incorporated into existing circuit architectures without requiring separate discrete components, thereby improving frequency performance while controlling integration complexity

Inventive Principle:

Principle #7Nested doll (Nesting)

2Strength

If piezoelectric material units are formed with protection layer, then mechanical strength is improved, but manufacturing steps increase

Engineering Contradiction:

Improvemechanical strengthVSAvoidfabrication process

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

A protection layer is formed conformally over the piezoelectric material units at an early stage in the fabrication process, before subsequent processing steps. This preliminary protective measure prevents mechanical damage during handling and processing, improving mechanical strength without requiring additional complex manufacturing steps later in the process

Inventive Principle:

Principle #10Preliminary action

3Loss of energy

If absorbing layer with air-gap regions is used, then acoustic wave absorption is improved, but fabrication complexity increases

Engineering Contradiction:

Improveacoustic wave absorptionVSAvoidlayer structure complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The absorbing layer incorporates air-gap regions that create a porous or cellular structure within the layer. This porous configuration enhances acoustic wave absorption by providing multiple interfaces for wave scattering and energy dissipation. The air-gaps are integrated into the layer structure through standard fabrication techniques, managing the complexity of the multi-layer configuration while achieving superior acoustic performance

Inventive Principle:

Principle #31Porous materials

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 solution provides a robust and efficient integration of BAW filters with circuit substrates, offering mechanical support, electrical connectivity, and thermal dissipation, suitable for high-frequency operations.

Implementation Method 1

A plurality of piezoelectric material units are disposed on the first electrode layer

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

An absorbing layer is disposed on the buffer layer. A plurality of piezoelectric material units are disposed on the first electrode layer

Methodology Applied

Scientific EffectAcoustic absorption: Acoustic Absorption

Data Source

PatentUS12593612B2Structure of semiconductor device and method for fabricating the same

Publication Date: 2026.03.31 UNITED MICROELECTRONICS CORP

AI summary

A structure of a semiconductor device is provided, including a circuit substrate. A first metal bulk layer is disposed on the circuit substrate. A buffer layer is disposed on the first metal bulk layer. An absorbing layer is disposed on the buffer layer. A first electrode layer is disposed on the absorbing layer. A plurality of piezoelectric material units are disposed on the first electrode layer. A protection layer is conformally disposed on the piezoelectric material units. A second metal bulk layer is disposed over the piezoelectric material units, and including a first part and a second part. The first part penetrating through the protection layer is disposed on the piezoelectric material units, serving as a second electrode layer. The second part is at a same level of the first part, and at least electrically connecting to the first electrode layer.