MEMS Getter Layer Placement for Vacuum Maintenance
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Solution Overview
Problem
Existing MEMS devices face challenges in maintaining a vacuum within their cavities for the desired lifetime while simplifying the production process, as previous methods are complex and prone to cross-pollution during localized deposition of gas-absorbing materials.
Innovation Solution
A MEMS device design featuring three layers where the mobile structure is defined within the second layer, with first and third-layer cavities that do not house the mobile structure, and a getter layer on the inner surface between the second and third layers to absorb gas molecules, ensuring a self-supporting structure for easier handling and reduced complexity in production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If localized deposition of gas-absorbing material is used to maintain vacuum, then vacuum maintenance is improved, but production process complexity increases and cross-pollution risk arises
Solution Approach 1:
The patent extracts the gas-absorbing material (getter) from its traditional localized deposition within the sealed cavity and places it on the outer surface of the sealed structure. This allows the getter to be applied using simple coating methods without requiring complex localized deposition processes, eliminating cross-pollution risks while maintaining vacuum effectiveness.
Solution Approach 2:
The patent introduces a porous layer as an intermediary between the getter material and the external environment. This porous layer allows gas molecules to diffuse through to the getter while preventing direct contact between the getter and external contaminants, enabling simple coating processes without cross-pollution concerns.
2Reliability
If getter layer is placed inside the sealed cavity, then vacuum maintenance is improved, but production complexity increases due to localized deposition requirements
Solution Approach 1:
The patent inverts the traditional approach by placing the getter layer on the external surface of the sealed cavity rather than inside it. This reversal allows the getter to be applied using simple external coating processes before sealing, eliminating the need for complex internal localized deposition while maintaining vacuum maintenance functionality.
Solution Approach 2:
The patent applies the getter layer to the sealed structure's external surface before the sealing process occurs. This preliminary action allows the getter to be deposited using simple coating methods on an accessible surface, avoiding the complexity of internal localized deposition that would be required if the getter were placed inside the cavity after sealing.
3Manufacturing precision
If complex localized deposition processes are used, then gas-absorbing material placement precision is improved, but production time and cross-pollution risk increase
Solution Approach 1:
The patent extracts the getter application process from the internal cavity environment and relocates it to the external surface. This allows the use of simple, fast coating processes that do not require precise localized deposition, significantly reducing production time while eliminating cross-pollution risks associated with complex deposition processes.
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 design effectively maintains a vacuum within the MEMS device by using a getter layer to absorb gas molecules, ensuring the device's longevity and simplifying the production process by avoiding the complexity of localized gas-absorbing material deposition.
Implementation Method 1
at least one getter layer arranged on the inner surface of said space between the second and the third layer... effectively maintains a vacuum within the MEMS device by using a getter layer to absorb gas molecules
Data Source
Figure 1~2
Figure 3a~3b
Figure 4a~4b
AI summary
A MEMS device comprises a first layer (1), a second layer (2) and a third layer (3) sealed together. A mobile structure (7.1, 7.2) in the second layer (2) is defined by openings (8.1, 8.2) in the second layer (2). In the first layer (1), there is at least one first-layer cavity (6.1, 6.2) with an opening towards the mobile structure (7.1, 7.2) of the second layer (2). In the third layer (3), there is at least one third-layer cavity (9) with an opening towards the mobile structure (7.1, 7.2) of the second layer (2). Therefore, the third-layer cavity (9) and the second layer (2) define a space within the MEMS device, A getter layer (10.1, 10.2) arranged on a surface of said space. The getter layer (10.1, 10.2) is preferably arranged on a surface of the second layer (2) and in particular, the getter layer (10.1, 10.2) is arranged on a static part of the second layer (2). Alternatively, the MEMS device has a third-layer cavity (24) with at least two recesses (25.1, 25.2, 25.3) and the getter layer (26.1, 26.2, 26.3) is arranged on a surface of the recesses (25.1, 25.2, 25.3).