Buried Electrode MEMS via Molecular Bonding and Segmentation
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Solution Overview
Problem
Current methods for producing micro and nano-systems, such as MEMS, face challenges including the inability to deposit monocrystalline silicon structural layers, degradation of mechanical properties in non-monocrystalline layers, and the need for costly and complex equipment for alignment and sealing processes.
Innovation Solution
A method involving molecular bonding of substrates with a monocrystalline intermediate substrate, allowing for the formation of a movable part between a lower electrode and an upper substrate, enabling alignment without special equipment and maintaining a flexible thermal budget, while providing electrical contact and hermetic sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If non-monocrystalline structural layers are deposited on insulating layers, then the manufacturing process can proceed, but the mechanical properties are degraded
Solution Approach 1:
The device is divided into three separate substrates (first substrate with lower electrode, intermediate substrate with mobile part, upper substrate), allowing each to be manufactured independently with optimal material properties. The intermediate substrate can be made of monocrystalline silicon with excellent mechanical properties, while being processed separately from the electrode substrates.
Solution Approach 2:
An intermediate substrate acts as a mediator between the lower and upper substrates. This intermediate substrate comprises the mobile part and is assembled by molecular bonding with the first substrate, enabling the use of monocrystalline silicon for the mobile structure without compromising the electrode fabrication process.
2Strength
If thick structural layers are deposited, then the structural integrity is improved, but the treatment time and cost increase significantly
Solution Approach 1:
The structure is segmented into multiple substrates where the intermediate substrate provides the necessary structural integrity for the mobile part. This eliminates the need for thick structural layers in the electrode substrates, reducing deposition time and cost while maintaining mechanical strength through the monocrystalline intermediate substrate.
3Ease of manufacture
If direct bonding of substrates is performed, then assembly is achieved, but alignment marks become buried and invisible for subsequent alignment
Solution Approach 1:
Alignment marks are transferred from the front face to the back face of the first substrate. This dimensional relocation allows the marks to remain visible after molecular bonding, as they are now on the opposite side of the substrate from where subsequent layers are deposited. The marks can be used for aligning the intermediate and upper substrates without being obscured.
4Strength
If monocrystalline silicon is used for structural layers, then mechanical properties are improved, but deposition on insulating layers is not possible
Solution Approach 1:
The device is segmented into separate substrates, allowing the intermediate substrate to be made of monocrystalline silicon processed independently. This eliminates the constraint of depositing monocrystalline silicon on insulating layers, as the monocrystalline substrate is prepared separately and then assembled via molecular bonding.
Solution Approach 2:
The intermediate substrate serves as an intermediary that provides monocrystalline silicon structure with excellent mechanical properties. It is assembled by molecular bonding with the first substrate, bypassing the limitation of direct deposition on insulating layers while maintaining the desired mechanical characteristics.
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 approach allows for the production of micro and nano-systems with improved mechanical properties and reduced thermal constraints, enabling efficient alignment and sealing without specialized equipment, thus enhancing the manufacturing efficiency and cost-effectiveness.
Implementation Method 1
an intermediate substrate comprising a mobile part, assembled, outside the mobile part, by molecular bonding with the first substrate
Data Source
Figure 1
Figure 2A~2D
Figure 2E~2G
AI summary
The device has a lower substrate (100) including a lower electrode (102) and a dielectric layer (103). An intermediate substrate (200) made of single-crystal silicon and extending along a main plane is assembled outside an oscillating mass (210) by molecular bonding with the lower substrate, where the oscillating mass is opposite to a portion of the lower electrode. An upper complementary metal oxide semiconductor (CMOS) substrate (300) is joined to the intermediate substrate, where the oscillating mass is released for movement between the lower electrode and the upper substrate. An independent claim is also included for a method for making a micro-system and/or nano-system type device.