Integrated MEMS Pressure Sensor and Accelerometer via Segmented Substrate
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Solution Overview
Problem
Integrating multiple MEMS structures for sensing different physical quantities into a single device is challenging due to conflicting operational requirements, such as the need for isolation in some sensors and environmental contact in others, which complicates the manufacturing process.
Innovation Solution
A manufacturing method that uses a substrate configuration with movable elements and cap structures to isolate certain sensors while allowing others to interact with the environment, enabling the integration of a pressure sensor and an accelerometer into a single MEMS device through a single process, where a movable membrane connected to a cap allows the sensor to sense pressure variations while protecting the movable element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple MEMS structures for sensing different physical quantities are integrated into a single device, then device functionality and versatility are improved, but manufacturing complexity and process difficulty increase due to conflicting operational requirements
Solution Approach 1:
The device is segmented into distinct functional regions: a first region containing an accelerometer with a movable element isolated from the environment, and a second region containing a pressure sensor with a movable element that contacts the environment. This spatial segmentation allows each sensor type to operate under its required conditions simultaneously within a single integrated device.
Solution Approach 2:
Different regions of the substrate are given different structural qualities to meet local sensing requirements. The accelerometer region includes a cap structure for isolation, while the pressure sensor region has an open structure for environmental contact. This local differentiation enables multiple sensing functions with conflicting requirements to coexist in one device.
2Reliability
If a cap structure is added to protect the movable element for sensing acceleration, then reliability and isolation are improved, but the ability to sense environmental pressure is reduced
Solution Approach 1:
The cap structure is selectively applied only to the accelerometer region, leaving the pressure sensor region open. This segmented approach allows the movable element in the accelerometer region to be protected and isolated, while the movable element in the pressure sensor region remains exposed to environmental pressure for sensing.
Solution Approach 2:
The cap structure provides localized protection to specific movable elements that require isolation (accelerometer), while other movable elements (pressure sensor) deliberately lack this protective feature to maintain environmental contact. This local quality differentiation resolves the conflict between protection and environmental interaction.
3Measurement precision
If the movable element is isolated from the external environment, then sensing accuracy for acceleration is improved, but pressure sensing capability is lost
Solution Approach 1:
The device substrate is divided into functionally independent regions: an isolated first region for high-precision acceleration sensing and a non-isolated second region for pressure sensing. This segmentation allows each sensor type to achieve its optimal measurement precision under its required environmental conditions without compromising the other.
Solution Approach 2:
Different environmental conditions are provided locally to different sensing regions: the accelerometer region maintains isolation for high precision, while the pressure sensor region maintains environmental contact for pressure measurement. This local quality approach enables both sensors to achieve their respective measurement precision requirements simultaneously.
Data Source
AI summary
A manufacturing method of microelectromechanical system (MEMS) device includes providing a first, a second and a third substrates, wherein the first substrate includes a first and a second circuit, the second substrate includes second and third connection areas, and the third substrate includes first connection areas. Second grooves and a dividing groove are formed on the fourth surface of the third substrate. The second and third substrates are bonded to make the first and the second connection areas correspondingly connect with each other. The second substrate is divided to form electrically isolating first and second movable elements. The first movable element is spatial separated from the third substrate and corresponding to the second groove. The second movable element is connected to the third substrate. The first and the second substrates are bonded to make the fourth and the third connection areas connect correspondingly. The third substrate is thinned, divided into a first and a second cap from the dividing groove, and formed a first groove from the fifth surface. The first cap is corresponding to the first movable element and the first circuit. Air tight space to sense a pressure variation of exterior environment is formed between the first substrate and the second cap. The second movable element is movable with the second cap by the pressure variation of the exterior environment. Accordingly, the pressure sensor and the MEMS structure for sensing other physical quantity can be integrated in the foregoing MEMS device by a single process.