Vertically Integrated MEMS Sensors with Isolated Cavities
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Solution Overview
Problem
Existing MEMS sensor devices face challenges in integrating multiple stimulus sensing capabilities within a miniaturized package without increasing manufacturing cost or complexity, while maintaining performance, for applications in automotive, medical, and consumer products.
Innovation Solution
The development of a microelectromechanical systems (MEMS) sensor device with vertically integrated sensors, utilizing a polysilicon to silicon bonding technique and stacked wafer configuration, allowing for separate isolated cavities with different pressures to optimize sensor operation, and incorporating electrically conductive through-silicon-vias to reduce device dimensions and enhance functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple stimulus sensing capabilities are integrated into the same package, then the sensing functionality and versatility are improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The device is divided into multiple separately fabricable wafer layers (first wafer layer, second wafer layer, third wafer layer), each containing specific sensor elements. These segmented layers are subsequently bonded together to form the complete multi-stimulus sensor device, allowing independent fabrication and optimization of each layer while achieving integrated functionality.
Solution Approach 2:
The patent transitions from lateral integration of sensors to vertical integration by stacking multiple wafer layers in the third dimension. This dimensional change allows multiple stimulus sensing capabilities to be achieved without increasing the lateral footprint, and enables separate fabrication of each layer before bonding, thereby reducing overall device complexity.
2Volume of moving object
If sensors are integrated into a miniaturized package, then the device size is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
By segmenting the device into multiple wafer layers that can be fabricated separately using standard MEMS processes, each layer can be manufactured with appropriate precision requirements. The final assembly through bonding achieves the miniaturized package without requiring the entire multi-stimulus structure to be fabricated in a single complex process.
Solution Approach 2:
Multiple wafer layers are prepared and pre-fabricated with their respective sensor elements before being bonded together. This preliminary action allows each layer to be optimized and fabricated independently with appropriate precision, avoiding the need for single-step high-precision fabrication of the complete multi-stimulus device.
3Measurement precision
If vertically integrated sensors with separate isolated cavities are implemented, then the sensor performance and sensitivity are improved, but the fabrication process complexity increases
Solution Approach 1:
The device structure is segmented into multiple wafer layers, with each layer containing specific sensor elements and their associated cavities. This segmentation allows each sensor type to have its optimized cavity structure and pressure environment, improving sensitivity while enabling separate fabrication of each layer before bonding.
Solution Approach 2:
By implementing separate isolated cavities in different wafer layers rather than attempting to create complex three-dimensional cavity structures within a single layer, the patent achieves improved sensor performance through vertical stacking. This dimensional approach simplifies the fabrication process for each individual cavity while maintaining the benefits of isolated pressure environments.
Data Source
AI summary
A device includes vertically and laterally spaced sensors that sense different physical stimuli. Fabrication of the device entails forming a device structure having a first and second wafer layers with a signal routing layer interposed between them. Active transducer elements of one or more sensors are formed in the first wafer layer and a third wafer layer is attached with the second wafer layer to produce one or more cavities in which the active transducer elements are located. A trench extends through the second wafer and through a portion of the signal routing layer. The trench electrically isolates a region of the second wafer layer surrounded by the trench from a remainder of the second wafer layer. Another active transducer element of another sensor is formed in this region. The transducer element formed in the second wafer layer may be a diaphragm for a pressure sensor of the sensor device.