Acoustic Wave Packaging With Etch-Stop Through-Hole Control
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Solution Overview
Problem
In acoustic wave devices with wafer-level packaging, the shape and depth of through-holes in silicon substrates vary due to conventional dry etching methods, leading to inconsistent device performance.
Innovation Solution
Incorporating an etching stop layer with a metal material having a lower etching rate than the silicon substrate, such as Ti, AlCu, or Pt, to stabilize the shape and depth of through-holes during dry etching, ensuring consistent acoustic wave device manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If dry etching is used to form through-holes in Si substrate, then through-holes can be formed efficiently, but the shape and depth of through-holes vary due to difficulty in detecting bottom surface position
Solution Approach 1:
An etching stop layer is formed on the bottom surface of the through-hole before completing the etching process. This preliminary action provides a detectable endpoint that prevents over-etching and ensures consistent through-hole depth and shape across multiple devices.
Solution Approach 2:
The etching stop layer acts as an intermediary between the Si substrate and the underlying layer. It provides a distinct etching rate difference that allows for precise detection of the through-hole bottom surface position, thereby improving manufacturing precision without reducing productivity.
2Manufacturing precision
If etching time is adjusted by detecting bottom surface position using emission spectrometry, then through-hole depth can be controlled, but the shape and depth still vary
Solution Approach 1:
The invention replaces the reliance on emission spectrometry detection with a physical etching stop layer that provides a natural endpoint for the etching process. This substitution eliminates the variability associated with detection-based timing control and ensures consistent through-hole geometry.
Solution Approach 2:
By introducing an etching stop layer with different etching rate characteristics, the invention changes the etching process parameters to include a detectable endpoint. This parameter change enables more reliable and consistent control of through-hole depth and shape.
3Device complexity
If through-hole shape and depth are not stabilized, then manufacturing process is simple, but device performance becomes inconsistent
Solution Approach 1:
The etching stop layer is formed as a preliminary step before through-hole etching. This simple additional layer provides a reliable endpoint that stabilizes through-hole geometry and ensures consistent device performance without significantly complicating the manufacturing process.
Solution Approach 2:
The etching stop layer serves as an intermediary that bridges the simplicity of the etching process with the requirement for precise through-hole control. It enables consistent device performance by providing a natural stopping point for etching while maintaining process simplicity.
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 use of an etching stop layer with a lower etching rate stabilizes the shape and depth of through-holes, enhancing the consistency and performance of acoustic wave devices by reducing variations in etching processes.
Implementation Method 1
an etching stop layer between the via electrode and the wiring layer, in which the etching stop layer includes a metal material with an etching rate lower than an etching rate of the second substrate
Data Source
AI summary
An acoustic wave device includes a first substrate, a piezoelectric layer including first and second main surfaces facing a thickness direction of the first substrate, the first main surface facing the first substrate, a functional electrode on at least one of the first or second main surfaces, a second substrate including a third main surface and a fourth main surface facing the thickness direction and a through-hole penetrating from the third main surface to the fourth main surface, the third main surface facing the second main surface of the piezoelectric layer, a via electrode in the through-hole, a wiring layer between the piezoelectric layer and the second substrate and electrically connecting the functional electrode and the via electrode, and an etching stop layer between the via electrode and the wiring layer and including a metal material with an etching rate lower than that of the second substrate.