MEMS Pressure Sensor Multi-Wafer Integration
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Solution Overview
Problem
Existing MEMS pressure sensors face challenges in achieving high performance and integration with inertial measurement units due to mechanical noise and drift, requiring additional sensors like pressure sensors for accurate navigation, which complicates packaging and increases size and cost.
Innovation Solution
A MEMS pressure sensor design integrated into a 3D System Chip using a multi-wafer stack structure with a top cap, MEMS wafer, and bottom cap, featuring insulated conducting pathways for wire-bond-free electrical connections, allowing for hermetic sealing and vacuum conditions, enabling efficient signal routing and integration with ICs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional pressure sensors are added to augment MEMS inertial capability for navigation applications, then measurement precision and reliability are improved, but device complexity and packaging difficulty increase
Solution Approach 1:
The patent combines the pressure sensor and inertial measurement unit into a single integrated device, merging previously separate sensors into one unified package. This integration eliminates the need for separate packaging of multiple sensors while maintaining the ability to perform both pressure measurement and inertial sensing, thereby improving navigation accuracy without proportionally increasing packaging complexity
Solution Approach 2:
The integrated device performs multiple functions: pressure sensing, acceleration measurement, and angular rate sensing. By making the device universal and capable of multiple measurement types, the patent reduces the overall system complexity that would otherwise require multiple separate sensors, each needing individual packaging and integration
2Ease of manufacture
If wire bonding is used for electrical connections in traditional MEMS sensors, then ease of manufacture is improved, but device complexity and size increase
Solution Approach 1:
The patent extracts and eliminates the wire bonding step from the manufacturing process by implementing direct electrical connections through conductive pathways integrated into the substrate. This removal of the wire bonding operation simplifies the overall manufacturing process while reducing the interconnection structure complexity and associated device size
Solution Approach 2:
The patent introduces integrated conductive pathways as an intermediary structure that provides electrical connections without requiring external wire bonding. These pathways are formed as part of the substrate structure itself, serving as a built-in mediator for electrical signal transmission and simplifying both manufacturing and device architecture
3Measurement precision
If hermetic sealing is implemented for vacuum conditions in MEMS pressure sensors, then measurement precision is improved, but manufacturing precision and cost increase
Solution Approach 1:
The patent combines the hermetic sealing function with the structural components of the device, integrating the seal into the substrate and cap assembly rather than treating it as a separate manufacturing step. This integration maintains vacuum conditions for accurate pressure measurement while reducing the overall manufacturing precision requirements compared to separate sealing operations
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 design enhances the performance of MEMS pressure sensors by reducing noise and drift, enabling more accurate navigation while minimizing size and cost through efficient packaging and integration with inertial sensors.
Implementation Method 1
The top cap electrode forms, together with the membrane, a variable capacitor across a vacuum gap to a second electrical contact
Implementation Method 2
A pressure difference across the membrane causes it to deflect
Data Source
AI summary
The present invention provides a MEMS pressure sensor and a manufacturing method. The pressure is formed by a top cap wafer, a MEMS wafer and a bottom cap wafer. The MEMS wafer comprises a frame and a membrane, the frame defining a cavity. The membrane is suspended by the frame over the cavity. The bottom cap wafer closes the cavity. The top cap wafer has a recess defining with the membrane a capacitance gap. The top cap wafer comprises a top cap electrode located over the membrane and forming, together with the membrane, a capacitor to detect a deflection of the membrane. Electrical contacts on the top cap wafer are connected to the top cap electrode. A vent extends from outside of the sensor into the cavity or the capacitance gap. The pressure sensor can include two cavities and two capacitance gaps to form a differential pressure sensor.