MEMS Cavity Encapsulation Using PVD to Avoid Internal Coating
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Solution Overview
Problem
Conformal deposition in chemical vapor deposition (CVD) processes leads to unwanted coating of microscale features inside MEMS devices, disrupting electrical connections and device operation.
Innovation Solution
Employing physical vapor deposition (PVD) for encapsulation, which is less conformal, forming islands of dielectric material outside the cavity and avoiding coating of internal features, ensuring hermetic sealing without interfering with device operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chemical vapor deposition (CVD) is used for encapsulation, then hermetic sealing is achieved, but unwanted coating of microscale features inside the cavity occurs, disrupting electrical connections
Solution Approach 1:
The patent changes the deposition process parameter from chemical vapor deposition to physical vapor deposition. This parameter change fundamentally alters the deposition characteristics, allowing the film to be deposited only on surfaces exposed to the deposition chamber (external surfaces) while avoiding coating of internal microscale features that are not exposed to the chamber environment.
Solution Approach 2:
The patent extracts the harmful conformal deposition characteristic from the encapsulation process. By using PVD instead of CVD, the process selectively deposits film only where needed (on external surfaces for hermetic sealing) while excluding the unwanted coating effect from internal cavity features.
2Manufacturing precision
If conformal deposition is used for encapsulation, then complete coverage is achieved, but coating of internal features disrupts device operation
Solution Approach 1:
The patent applies local quality by making the deposition process non-conformal. The film is deposited only on specific local areas (external surfaces of the device structure) rather than uniformly on all surfaces. This allows hermetic sealing where needed while avoiding coating of internal features that would disrupt device operation.
3Reliability
If CVD process is used for encapsulation, then hermetic protection is provided, but package size and cost increase
Solution Approach 1:
The patent extracts the hermetic sealing function from the CVD process and implements it through PVD. This extraction allows for a simplified package structure that achieves the same hermetic protection with reduced complexity, smaller package size, and lower cost.
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
PVD-based encapsulation prevents unwanted coating on sensitive microscale features, maintaining electrical connectivity and reducing package size and cost while providing effective hermetic protection.
Implementation Method 1
sealing at least a portion of the MEMS device including the one or more release holes with a film utilizing a physical vapor deposition (PVD) process
Data Source
AI summary
A method includes forming a microelectromechanical system (MEMS) device wherein the MEMS device includes a cavity and one or more release holes extending from a surface of the MEMS device to the cavity, and sealing at least a portion of the MEMS device including the one or more release holes with a film utilizing a physical vapor deposition (PVD) process.