Etching-Resistant Wall Structure for Pressure Sensor Cavity Airtightness
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Solution Overview
Problem
Existing electronic devices with cavities formed using semiconductor manufacturing processes face issues with airtightness due to unexpected etching caused by etchant permeation through gaps with masks during wet etching, leading to reduced reliability.
Innovation Solution
The implementation of an electronic device with a substrate, a functional element, and a wall portion comprising an insulating layer surrounded by etching-resistant layers that are coupled to each other, reducing the risk of etchant penetration and enhancing airtightness by forming a stable wall structure with a metal layer, such as aluminum, and using silicon oxide as an insulating layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wet etching is used to form the cavity, then manufacturing efficiency is improved, but etchant permeates through gaps with masks causing unexpected etching and reducing airtightness
Solution Approach 1:
The patent introduces an etching-resistant layer as an intermediary protective barrier between the insulating layer and the etchant. This layer prevents direct contact between the etchant and insulating layer, thereby preventing unexpected etching while allowing the wet etching process to proceed efficiently for cavity formation.
Solution Approach 2:
The patent employs a composite structure consisting of multiple layers with different properties: an insulating layer (silicon oxide) and an etching-resistant layer. This composite material approach combines the insulating properties of silicon oxide with the etchant resistance of the additional layer, achieving both electrical insulation and protection against etchant penetration.
2Device complexity
If the wall portion uses only an insulating layer, then manufacturing simplicity is maintained, but the wall portion is etched by etchant reducing airtightness
Solution Approach 1:
The patent segments the wall portion into two distinct functional layers: an insulating layer and an etching-resistant layer. This segmentation allows each layer to perform its specific function - the insulating layer provides electrical insulation while the etching-resistant layer provides protection against etchant, thereby maintaining airtightness without significantly complicating the manufacturing process.
3Reliability
If multiple etching resistant layers are added to surround the insulating layer, then protection against etchant is improved, but device complexity increases
Solution Approach 1:
The patent extracts the etching resistance function from the insulating layer by adding a dedicated etching-resistant layer. This separation of functions allows the insulating layer to focus on electrical insulation while the etching-resistant layer handles chemical protection, achieving reliable protection without requiring complex multi-layer configurations.
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 configuration enhances the reliability of the electronic device by preventing etching of the insulating layer, maintaining airtightness, and improving the accuracy of the wall formation, thereby reducing unexpected etching and increasing the adhesiveness between layers.
Implementation Method 1
a plurality of etching resistant layers having higher resistance to an etchant which can etch the insulating layer than resistance of the insulating layer
Data Source
AI summary
An physical quantity sensor includes a substrate, a piezoelectric resistive element that is disposed on one surface side of the substrate, a wall portion that is disposed on the one surface side of the substrate so as to surround the piezoelectric resistive element in a plan view of the substrate, and a ceiling portion that is disposed on an opposite side to the substrate with respect to the wall portion and forms a cavity along with the wall portion, in which the wall portion includes an insulating layer, and wiring layers that surround the insulating layer together and have higher resistance to an etchant which can etch the insulating layer than resistance of the insulating layer.