BAW Resonator Metal Bonding Layer Grounding for Heat Dissipation

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Solution Overview

Problem

Conventional bonding processes for bulk acoustic wave (BAW) resonators, such as SiO2—Si or Si—Si bonding, have strict material and surface roughness requirements, are difficult to control, and can negatively impact resonator performance when a metal bonding layer is present under the cavity.

Innovation Solution

A metal bonding layer is grounded by connecting it to a ground pad metal layer through a grounded through hole in the piezoelectric layer, using eutectic or metal diffusion bonding, which helps in heat dissipation and improves radio frequency power withstand capability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional bonding processes (SiO2-Si or Si-Si) are used for BAW resonators, then bonding can be achieved, but the process is difficult to control and negatively impacts resonator performance when metal bonding layer is present

Engineering Contradiction:

Improvebonding qualityVSAvoidprocess difficulty

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent extracts the metal bonding layer from the bonding interface by removing it before the bonding process, then replaces it with a new metal bonding layer formed after bonding. This eliminates the harmful effect of the original metal layer on bonding quality while maintaining the necessary bonding functionality.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent performs preliminary removal of the metal bonding layer before bonding, and preliminary formation of a new metal bonding layer after bonding. This sequence of preliminary actions ensures that the bonding process occurs without the harmful metal layer present, thereby improving both bonding quality and process controllability.

Inventive Principle:

Principle #10Preliminary action

2Strength

If metal bonding layer is present under the cavity, then bonding can be achieved, but resonator performance degrades

Engineering Contradiction:

Improvebonding strengthVSAvoidresonator performance

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent extracts the harmful metal bonding layer from under the cavity before bonding, eliminating its negative impact on resonator performance. A new metal bonding layer is then formed after bonding to provide necessary electrical connection without degrading performance.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent provides beforehand cushioning by removing the harmful metal layer prior to bonding, preventing performance degradation before it occurs. The subsequent formation of a new metal bonding layer ensures proper electrical connection is established in advance.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If conventional bonding processes are used, then bonding can be achieved, but surface roughness requirements are strict

Engineering Contradiction:

Improvebonding achievementVSAvoidsurface roughness requirement

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent removes the metal bonding layer that causes strict surface roughness requirements before bonding. This extraction eliminates the source of the precision requirement, allowing bonding to proceed with more relaxed surface specifications.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent performs preliminary removal of the metal bonding layer before the bonding process, eliminating the strict surface roughness requirements in advance. This preliminary action simplifies the manufacturing precision requirements for the bonding step.

Inventive Principle:

Principle #10Preliminary action

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 grounded metal bonding layer reduces performance degradation and enhances heat dissipation, improving the quality and performance of BAW resonators.

Implementation Method 1

Methodology Applied

Scientific EffectHeat dissipation: Conduction (thermal)

Implementation Method 2

using eutectic or metal diffusion bonding

Methodology Applied

Scientific EffectEutectic bonding: Welding

Implementation Method 3

using eutectic or metal diffusion bonding

Methodology Applied

Scientific EffectMetal diffusion bonding: Diffusion Welding

Data Source

PatentUS12355420B2Bulk acoustic wave resonator with metal bonding layer

Publication Date: 2025.07.08 SHENZHEN NEWSONIC TECH CO LTD

AI summary

A bulk acoustic wave (BAW) resonator includes: a substrate; a piezoelectric layer disposed above the substrate; a first electrode disposed below the piezoelectric layer and including a first portion and a second portion spaced apart from each other; a second electrode disposed above the piezoelectric layer; a first dielectric layer, a second dielectric layer, and a third dielectric layer sequentially disposed between the substrate and the piezoelectric layer in an order from the piezoelectric layer to the substrate; a cavity disposed below the first portion of the first electrode; a metal bonding layer disposed between the third dielectric layer and the substrate; and a ground pad metal layer disposed on the piezoelectric layer and electrically connected to the metal bonding layer.