MEMS Cavern Resealing With Laser-Shielding Protective Layers
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Solution Overview
Problem
Conventional laser reseal methods for MEMS-based sensors require prestructuring of the cap substrate, leading to issues like polymer particle loading, hydrogen escape, and damage to electronic circuits, which are not addressed by existing techniques.
Innovation Solution
A method that absorbs and/or reflects laser radiation using protective material between the MEMS substrate and cap part, avoiding impingement on regions with electronic circuits, and employs trench etching and gas phase etching to create cavern access without prestructuring the cap substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional laser reseal method is used to seal caverns in MEMS-based sensors, then hermetic sealing of caverns is achieved, but prestructuring and recessing of cap substrate is required which leads to polymer particle loading, hydrogen escape, and damage to electronic circuits
Solution Approach 1:
A sacrificial layer is introduced as an intermediary element between the laser beam and the cap substrate. This layer absorbs or scatters the laser radiation, preventing direct impingement on the cap substrate and electronic circuits. The sacrificial layer is temporarily present during laser resealing and is subsequently removed, having served its protective function during the sealing process.
Solution Approach 2:
The harmful effect of laser radiation on the cap substrate is extracted or isolated by introducing the sacrificial layer. Instead of directly exposing the cap substrate to laser radiation, the sacrificial layer is positioned to intercept and remove the harmful radiation before it reaches the cap substrate, thereby protecting the electronic circuits and avoiding processing complications.
2Ease of operation
If prestructuring of cap substrate is performed to enable laser resealing, then cavern access for pressure setting is achieved, but electronic circuits on cap substrate are exposed to laser radiation and processing damage
Solution Approach 1:
The sacrificial layer acts as a mediator that enables cavern access operations while protecting electronic circuits. During laser resealing, the sacrificial layer is positioned to block laser radiation from reaching the cap substrate, allowing hermetic sealing to proceed without damaging the electronic circuits. The sacrificial layer is then removed after serving its protective purpose.
Solution Approach 2:
The sacrificial layer provides beforehand cushioning or protection against laser radiation damage. By placing the sacrificial layer in advance before laser resealing, it cushions or absorbs the harmful laser energy, preventing direct exposure of the cap substrate and electronic circuits to the laser beam, thereby ensuring their integrity throughout the sealing process.
3Use of energy by moving object
If cap substrate is recessed in reseal region to facilitate laser sealing, then laser access to cavern openings is improved, but regions useful for electronic circuits are lost and processing complexity increases
Solution Approach 1:
The sacrificial layer serves as an intermediary that enables effective laser energy delivery without requiring complex cap substrate structuring. Instead of recessing the cap substrate to improve laser access, the sacrificial layer is positioned to manage laser radiation, allowing hermetic sealing to proceed with standard cap substrate configurations and simpler processing steps.
Solution Approach 2:
Instead of modifying the cap substrate to improve laser access (recessing or prestructuring), the approach is inverted by introducing a sacrificial layer that manages laser radiation interaction. This inversion eliminates the need for complex cap substrate modifications while still achieving effective laser sealing, thereby reducing device complexity and processing steps.
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
Protects electronic circuits from laser radiation and reduces processing complications, enabling efficient cavern pressure setting without damaging the cap substrate or altering internal pressures.
Implementation Method 1
protective material that lies between the MEMS substrate and the cap part... is absorbed and/or reflected and/or scattered by protective material
Implementation Method 2
protective material that lies between the MEMS substrate and the cap part... is absorbed and/or reflected and/or scattered by protective material
Implementation Method 3
reseal these caverns hermetically by melting shut a cavern access opening by means of laser irradiation
Data Source
AI summary
A micromechanical device and a method for producing a micromechanical device. The micromechanical device includes a MEMS substrate, a functional layer, and a cap part. The functional layer is located between the MEMS substrate and the cap part. The cap part includes a cap substrate. The micromechanical device has a main extension plane. The micromechanical system and the cap part enclose a cavern. The micromechanical device has a sealed cavern access.