Nanoliter Gas Sampling for MEMS Hermeticity Testing
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Solution Overview
Problem
Current techniques for hermetic encapsulation of MEMS devices are costly and inefficient, requiring cumbersome methods for evaluating hermeticity, especially when dealing with ultra-small gas volumes, which are difficult to analyze for leaks and impurities.
Innovation Solution
A sampling device and system capable of analyzing gas volumes as low as several nanoliters, featuring a modular design to accommodate varying package geometries, with hermetically sealed sections and fluidic connections to evacuate and analyze gases from MEMS packages, using a vacuum system and gas analysis instruments like mass spectrometers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hermetic encapsulation techniques (soldering, eutectic metal bonding, wafer fusion) are used for MEMS devices, then sealing reliability is improved, but manufacturing cost and process complexity increase significantly
Solution Approach 1:
The device is divided into a cover portion and a base portion that can be separately fabricated and then hermetically sealed together. This segmentation allows each part to be optimized independently while maintaining overall hermeticity, reducing the complexity of fabricating the entire structure as one piece.
Solution Approach 2:
An anodically bonded glass seal is introduced as an intermediary bonding layer between metal components. This glass intermediary enables hermetic sealing at lower temperatures compared to direct metal-to-metal bonding, simplifying the manufacturing process and reducing thermal stress while maintaining sealing reliability.
2Loss of time
If sub-set sampling is performed for hermeticity testing, then testing time is reduced, but measurement precision deteriorates due to statistical representation limitations
Solution Approach 1:
Getters are pre-installed inside the sealed package before final hermetic sealing. These getters continuously pump residual gases and potential leak infiltrates throughout the package lifetime, enabling long-term hermeticity monitoring without requiring frequent destructive testing, thus saving time while maintaining assessment accuracy.
3Adaptability or versatility
If gas analysis is performed on ultra-small volumes (nanoliters), then applicability to miniaturized MEMS packages is improved, but measurement precision deteriorates due to limited sample size
Solution Approach 1:
Getters are strategically positioned in specific locations within the package where they can most effectively pump residual gases and detect leaks. This localized placement optimizes the gas management function within the constrained nanoliter volume, maintaining measurement precision despite the ultra-small scale.
Solution Approach 2:
The system is designed to operate with gas volumes reduced from milliliter to nanoliter scale. By changing the volume parameter and adapting the analysis methodology accordingly, the system maintains measurement precision while becoming applicable to miniaturized MEMS packages.
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
Enables precise determination of hermeticity in MEMS packages with small gas volumes, ensuring the integrity of the sealed environment by accurately detecting leaks and impurities, thereby reducing costs and improving reliability.
Implementation Method 1
The sampling device must be capable of being sealed to a vacuum (typically to a pressure less than 10−8 Torr) to isolate the package
Implementation Method 2
analyzed to determine if gases other than those originally sealed in the package are present
Data Source
AI summary
A system is provided for testing the hermeticity of a package, such as a microelectromechanical systems package containing a sealed gas volume, with a sampling device that has the capability to isolate the package and breach the gas seal connected to a pulse valve that can controllably transmit small volumes down to 2 nanoliters to a gas chamber for analysis using gas chromatography/mass spectroscopy diagnostics.