CMOS-MEMS Device With Selective Outgassing For Multi-Pressure Enclosures
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Solution Overview
Problem
Implementing multiple sensors in a single CMOS-MEMS integrated device poses a challenge in providing different enclosure pressures to optimize each sensor's performance, as sensors like accelerometers require high pressure for immunity to acoustic vibrations while gyroscopes need lower pressure.
Innovation Solution
The integration of an outgassing source and outgassing barrier layers in the CMOS wafer allows for the creation of multiple enclosures with varying pressures, where the outgassing source is exposed in high-pressure regions and encapsulated in low-pressure regions, enabling the fabrication of CMOS-MEMS devices with eutectic wafer bonding and electrical interconnection for multi-ambient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple sensors are integrated in a single CMOS-MEMS device, then device functionality and versatility are improved, but the ability to provide different enclosure pressures for each sensor deteriorates
Solution Approach 1:
The patent divides the enclosure into multiple sealed cavities, each capable of maintaining different pressure levels. The outgassing source layer is selectively exposed in specific regions corresponding to different sensors, allowing independent pressure control for accelerometers (higher pressure) and gyroscopes (lower pressure) within the same integrated device
Solution Approach 2:
The outgassing barrier layer is selectively applied to different regions of the outgassing source layer, creating local variations in gas permeability. This enables different enclosure pressures in different areas of the device, with each sensor region having optimized pressure characteristics for its specific operational requirements
2Ease of manufacture
If uniform enclosure pressure is applied to all sensors, then manufacturing simplicity is improved, but sensor performance optimization deteriorates
Solution Approach 1:
The outgassing source layer and barrier layer are deposited and patterned during the CMOS fabrication process before final device assembly. This preliminary structuring of gas permeability regions enables subsequent pressure differentiation without requiring complex post-manufacturing interventions
Solution Approach 2:
The patent modifies the physical-chemical properties of the enclosure by controlling gas permeability through the outgassing barrier layer. By varying the presence and characteristics of this layer in different regions, the pressure parameters of each sensor enclosure are independently optimized for maximum sensor performance
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 enables the creation of CMOS-MEMS devices with distinct enclosure pressures, enhancing sensor accuracy by allowing independent optimization of each sensor's environment, with pressures differing by up to 50% between enclosures.
Implementation Method 1
An outgassing source layer is disposed over the bonding layer
Implementation Method 2
an outgassing barrier layer to encapsulate the outgassing source layer
Implementation Method 3
with eutectic wafer bonding and electrical interconnection for multi-ambient operation
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
An integrated MEMS device comprises two substrates where the first and second substrates are coupled together and have two enclosures there between. One of the first and second substrates includes an outgassing source layer and an outgassing barrier layer to adjust pressure within the two enclosures. The method includes depositing and patterning an outgassing source layer and a first outgassing barrier layer on the substrate, resulting in two cross-sections. In one of the two cross-sections a top surface of the outgassing source layer is not covered by the outgassing barrier layer and in the other of the two cross-sections the outgassing source layer is encapsulated in the outgassing barrier layer. The method also includes depositing conformally a second outgassing barrier layer and etching the second outgassing barrier layer such that a spacer of the second outgassing barrier layer is left on sidewalls of the outgassing source layer.