Getter Material Trenches for High Vacuum MEMS Encapsulation
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Solution Overview
Problem
Existing encapsulation structures for micro-devices like MEMS and NEMS face challenges in achieving a large surface area of getter material within a hermetically sealed cavity while minimizing the occupied surface area and accommodating irregular reception surfaces, which can limit the ability to maintain high vacuum conditions.
Innovation Solution
The encapsulation structure incorporates trenches on the substrate surface where getter material is deposited on the side walls, allowing for a larger exposed surface area without increasing the substrate's surface area, and includes communication between trench volumes for enhanced gas absorption and adsorption capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If getter material is deposited as a monolithic portion on the substrate, then the production process is simple, but the surface area of getter material exposed in the cavity is limited
Solution Approach 1:
The getter material is deposited on the side walls of trenches formed in the substrate, transitioning from a planar 2D surface to a 3D vertical surface. This dimensional change allows the getter material to occupy minimal substrate surface area while providing large exposed surface area in the cavity for gas absorption, directly resolving the technical contradiction between maximizing getter surface area and minimizing substrate occupation.
2Area of moving object
If getter material is deposited on irregular reception surfaces, then the substrate geometry is flexible, but the surface area for gas absorption is reduced
Solution Approach 1:
By depositing getter material on the vertical side walls of trenches rather than on the horizontal substrate surface, the invention transforms the problem of irregular reception surfaces into a solution. The trench structure provides vertical surfaces that can be formed on irregular substrates, maintaining both surface area for gas absorption and adaptability to irregular substrate geometries simultaneously.
3Reliability
If trenches are formed in the substrate and getter material is deposited on side walls, then gas pumping capacity is enhanced, but the device structure becomes more complex
Solution Approach 1:
The substrate is segmented by forming trenches that divide the surface into distinct regions. This segmentation creates vertical side walls that increase the getter material surface area while maintaining a relatively simple overall device structure. The trenches can be formed using standard semiconductor fabrication processes, minimizing the increase in device complexity while significantly enhancing vacuum maintenance capability.
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 achieves a higher gas pumping capacity with reduced bulk getter material, supports high vacuum conditions (up to 10^-4 to 10^-3 mbar), and allows for flexible geometry adjustments to optimize absorption and adsorption properties, while maintaining compatibility with both W2W and TFP encapsulation methods.
Implementation Method 1
The addition of non-evaporable getters (NEG) in the cavities, for example in the form of solid portions of getter material placed in these cavities, makes it possible to control the characteristics of the atmosphere within the cavities via gas pumping carried out by these getters.
Implementation Method 2
only the face opposite to that in contact with the substrate on which the getter is deposited is in contact with the atmosphere of the cavity
Data Source
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AI summary
Encapsulation structure comprising at least: - a hermetically sealed cavity in which a micro-device is encapsulated, - a substrate (102) of which one face (115) delimits one side of the cavity, - at least two trenches (116) formed through said face of the substrate, the interior volumes of each of the trenches communicating with each other, - first portions of getter material (112) covering at least part of the lateral walls of the trenches without completely filling the trenches, and completely covering the trenches at the level of said face of the substrate, - an opening (130) made through one of the first portions of getter material or through the substrate and making the interior volumes of the trenches communicate with an interior volume of the cavity.