MEMS Device Segmented Bonding for Pressure Control
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Solution Overview
Problem
Existing manufacturing processes for combined microelectromechanical (MEMS) devices face challenges in achieving distinct pressure values within hermetic cavities, leading to cross-talk and reduced accuracy of sensing signals.
Innovation Solution
The process involves forming a raised frame around the cavity requiring a specific pressure, activating a getter region within this cavity before bonding, and using a bonding region to seal the cavities in stages, thereby controlling pressure and minimizing cross-talk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a getter region is introduced into a hermetic cavity to adjust pressure, then the pressure control is improved, but cross-talk between cavities occurs and manufacturing precision deteriorates
Solution Approach 1:
The bonding process is segmented into multiple sequential stages: first bonding the cap to the substrate to seal the first cavity, then subsequently bonding to seal the second cavity. This temporal segmentation ensures that the getter region in the first cavity activates and stabilizes pressure before the second cavity is sealed, preventing cross-talk between cavities.
Solution Approach 2:
The getter region is activated and the first cavity is sealed with the desired pressure established before the second cavity is bonded and sealed. This preliminary action ensures that the pressure control mechanism is in place and stable before the second cavity is introduced, eliminating the risk of pressure interference between cavities.
2Device complexity
If hermetic cavities are bonded simultaneously, then manufacturing complexity is reduced, but pressure differentiation between cavities is lost
Solution Approach 1:
The bonding process is divided into sequential stages rather than simultaneous bonding. The first cavity is sealed and pressurized in the first stage, then the second cavity is sealed in a subsequent stage. This segmentation maintains pressure differentiation while keeping the manufacturing process manageable through clear process steps.
Solution Approach 2:
The first cavity is sealed and its pressure is established as a preliminary action before the second cavity is sealed. This ensures that when both cavities are present in the final device, they maintain different pressure values, achieving pressure differentiation without excessive 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
This approach effectively reduces cross-talk between hermetic cavities, allowing for precise control of pressure values and enhancing the accuracy of sensing signals in combined MEMS devices.
Implementation Method 1
activation of the getter region allows the pressure inside the cavity in which it is inserted to be reduced, attracting the non-noble gas species present in the same cavity
Data Source
AI summary
A process for manufacturing a combined microelectromechanical device envisages: forming, in a sensor wafer, at least a first and a second microelectromechanical structures, at a main surface; forming, in a cap wafer, at least a first and a second cavities, at a respective main surface; forming a getter region inside the first cavity; bonding the main surfaces of the sensor and cap wafers by means of a bonding region, to define a first and a second hermetic environments for the microelectromechanical structures at different pressure values. A raised frame is formed, before the bonding step, in such a way as to be located around the first cavity; the bonding region determines the bonding of the sensor and cap wafers at the raised frame and the definition of the first hermetic environment associated with the first cavity, in a time interval prior to hermetic closure of the second cavity.