Acoustic Wave Through-Hole Layout With Near-Vertical Via Walls

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Solution Overview

Problem

Conventional acoustic wave devices with wafer-level packaging face challenges in reducing the area occupied by through-vias on the second surface of substrates, leading to impaired layout properties due to tapered through-holes formed by dry etching.

Innovation Solution

The acoustic wave device features a through-hole with a side surface inclination of 0° to 5° relative to the normal of the second surface, formed using isotropic etching and protective film deposition, reducing the area occupied by the through-via and improving substrate layout efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If dry etching is used to form tapered through-holes, then the through-holes can be formed effectively, but the area occupied by through-vias on the second surface increases, impairing layout properties

Engineering Contradiction:

Improvethrough-hole formationVSAvoidarea occupied by through-via on second surface

Core Design Contradiction:

Ease of manufactureVSArea of stationary object

Solution Approach 1:

The patent changes the etching parameters by switching from dry etching (which produces tapered holes) to wet etching (which produces substantially vertical holes). This parameter change in the etching process fundamentally alters the hole geometry, reducing the opening area on the second surface while maintaining effective through-hole formation.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Instead of accepting the conventional tapered hole geometry from dry etching, the patent inverts the approach by using wet etching to achieve substantially vertical hole walls. This inverted geometry approach reduces the opening area on the second surface, thereby improving layout properties without sacrificing manufacturing effectiveness.

Inventive Principle:

Principle #13The other way round (Inversion)

2Area of stationary object

If the area occupied by through-via is reduced, then layout properties improve, but manufacturing precision may be affected

Engineering Contradiction:

Improvearea occupied by through-via on second surfaceVSAvoidthrough-hole formation precision

Core Design Contradiction:

Area of stationary objectVSManufacturing precision

Solution Approach 1:

The patent employs wet etching with specific chemical solutions to achieve substantially vertical hole walls with high precision. The chemical etching parameters are controlled to maintain precise hole geometry while minimizing the opening area, thus improving layout properties without compromising manufacturing precision.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces a protective film as an intermediary element during the etching process. This film allows for precise control of the etching front, enabling the formation of substantially vertical hole walls with accurate dimensions even when the opening area is reduced, thereby maintaining manufacturing precision.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 approach effectively minimizes the area occupied by the through-via on the second surface, enhancing the layout properties of the substrate while maintaining favorable resonance characteristics and Q values even with reduced electrode pairs.

Implementation Method 1

a piezoelectric layer including one main surface facing the first substrate in a thickness direction of the first substrate and another main surface facing a direction opposite to the one main surface in the thickness direction

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

a through-hole is formed in the second main surface of the second substrate by repeatedly performing a step of performing isotropic etching

Methodology Applied

Scientific EffectIsotropic etching:

Implementation Method 3

a step of depositing a protective film on a side surface and a bottom surface of a hole formed by the isotropic etching

Methodology Applied

Scientific EffectDeposition: Deposition (physical)

Data Source

PatentUS20240250661A1Acoustic wave device and method of manufacturing acoustic wave device

Publication Date: 2024.07.25 MURATA MFG CO LTD

AI summary

An acoustic wave device includes a first substrate, a piezoelectric layer including one main surface facing the first substrate and another main surface facing a direction opposite to the one main surface, a functional electrode on at least one of the one and the other main surfaces, and a second substrate including a first main surface facing the other main surface of the piezoelectric layer, a second main surface facing a direction opposite to the first main surface, and a through-hole penetrating from the first main surface to the second main surface. An angle at which a side surface of the through-hole is inclined from the second main surface toward the first main surface is equal to or more than about 0° and equal to or less than about 5° based on a normal line with respect to the second main surface.