MEMS Wafer Encapsulation via Segmented Fusion Bonding
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Solution Overview
Problem
Conventional wafer bonding techniques for MEMS devices lead to leakage and parasitic buildup, which are not effectively addressed in existing technologies.
Innovation Solution
A wafer encapsulation method involving fusion bonding of caps with recessed and non-recessed surfaces to create cavities around MEMS components, using silicon oxide and crystalline surfaces for bonding, and incorporating via isolation regions to reduce parasitic leakage and capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional wafer bonding techniques are used to join wafers, then wafer encapsulation is achieved, but leakage and parasitic buildup occur
Solution Approach 1:
The bonding interface is segmented into multiple regions: a first bonding region with a first material (e.g., silicon oxide) and a second bonding region with a second material (e.g., crystalline silicon). This segmentation allows different materials to be used in different regions to simultaneously achieve hermetic sealing (preventing leakage) and reduce parasitic effects, resolving the contradiction between leakage prevention and parasitic buildup reduction
Solution Approach 2:
Different materials are applied locally at different bonding regions. The first bonding region uses a material optimized for hermetic sealing properties, while the second bonding region uses a material optimized for minimizing parasitic capacitance and leakage. This local differentiation allows each region to perform its specific function optimally, addressing both leakage prevention and parasitic reduction requirements
2Reliability
If wafer encapsulation is implemented, then device protection is achieved, but device complexity increases
Solution Approach 1:
Multiple functions are merged into the encapsulation structure: the bonding layers simultaneously provide mechanical bonding, hermetic sealing, and electrical isolation. The recessed region integration combines cavity formation with structural support functions. This merging reduces the need for separate components, thereby protecting the device while managing structural complexity
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
The method effectively reduces parasitic leakage and capacitance, enhancing the reliability and performance of MEMS devices by creating a robust encapsulation that supports multi-level electrical contacts and isolation trenches.
Implementation Method 1
The non-recessed surfaces of the top and bottom caps are fusion bond mated with the top and bottom surface of the device surrounding the device region to create top and bottom cavity over the device region
Data Source
AI summary
A microelectromechanical system (MEMS) device is disclosed. The MEMS device includes a device substrate having a MEMS component in a device region. A top cap is fusion bonded to the top surface of the device substrate and a bottom cap is fusion bonded to the bottom surface of the device substrate. The top and bottom caps encapsulate the MEMS components. A cap includes a via isolation which extends a thickness of the cap and surrounds the device region.