Bonded MEMS Resonator Cover Structure With Integrated Hermetic Isolation
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Solution Overview
Problem
Current microelectromechanical systems face challenges in effectively encapsulating and protecting delicate mechanical structures within hermetically sealed containers or semiconductor substrates, which can be prone to environmental interference and mechanical stress.
Innovation Solution
The development of microelectromechanical devices that utilize multiple substrates bonded together to form a chamber, where the mechanical structure is partially disposed, with trench isolation and counter-doped semiconductor materials to ensure electrical isolation and enhanced structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hermetically sealed metal or ceramic container is used to encapsulate the mechanical structure, then the mechanical structure is protected from environmental interference, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent changes the material parameters and structural configuration by using a semiconductor substrate with integrated cavity instead of a separate metal or ceramic container. The substrate itself is engineered with specific thickness parameters, doping profiles, and cavity geometries to provide both mechanical support and environmental protection, eliminating the need for additional hermetic sealing components.
Solution Approach 2:
The semiconductor substrate serves multiple functions simultaneously: it acts as the mechanical support structure, provides the hermetic seal through its intrinsic material properties, defines the chamber geometry, and integrates the electrical contacts. This multi-functionality reduces the overall device complexity by consolidating what would otherwise require separate components.
2Reliability
If the mechanical structure is sealed in a hermetically sealed container, then the operating environment is controlled, but the manufacturing process becomes more difficult
Solution Approach 1:
The patent merges the encapsulation function with the substrate fabrication process. The cavity is formed and the mechanical structure is released within the same substrate using standard semiconductor processing techniques such as sacrificial layer release and selective etching. This integration allows the hermetic seal to be created during normal manufacturing rather than requiring additional sealing operations.
3Reliability
If a semiconductor substrate with chamber is used to house the mechanical structure, then the encapsulation is robust, but electrical isolation becomes more challenging
Solution Approach 1:
The patent applies local quality by creating specifically doped regions within the semiconductor substrate. High-resistivity or lightly-doped regions are formed in areas where electrical isolation is needed, while other regions maintain their conductive properties for functional operation. This localized modification of electrical properties provides isolation where required without affecting the overall device functionality.
Solution Approach 2:
The semiconductor substrate itself acts as an intermediary that provides both mechanical support and electrical isolation. By carefully controlling the doping profile and creating intermediate resistance regions, the substrate mediates between the need for structural integrity and electrical isolation, eliminating the need for additional isolation layers or structures.
4Strength
If multiple substrates are bonded together to form a chamber, then the structural integrity is enhanced, but the manufacturing precision requirements increase
Solution Approach 1:
The patent incorporates preliminary alignment features directly into the substrate design before the bonding process. These features, such as alignment marks, recesses, or protrusions, are fabricated during substrate preparation and guide the bonding process, ensuring precise alignment without requiring high-precision positioning equipment during assembly.
Data Source
AI summary
A semiconductor layer having an opening and a MEMS resonator formed in the opening is disposed between first and second substrates to encapsulate the MEMS resonator. An electrical contact that extends from the opening to an exterior of the MEMS device is formed at least in part within the semiconductor layer and at least in part within the first substrate.