MEMS Sensor Media Access via Grinding and Trenches
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Solution Overview
Problem
The production of micromechanical sensors, particularly pressure sensors, faces challenges in creating a media access point without damaging the ASIC wafer due to gas phase etching, which can harm the rear side of the ASIC, and existing methods like backside or side ports are technically complex or inefficient.
Innovation Solution
A method involving forming etching trenches in the MEMS substrate, bonding with a cap wafer, and creating a media access point by grinding the MEMS substrate, which protects the diaphragm area from environmental influences and avoids gas phase etching, allowing for a more straightforward and cost-effective manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If gas phase etching is used to create a media access point, then the etching process can reach the diaphragm area, but the rear side of the ASIC wafer and wafer edge are damaged
Solution Approach 1:
The wafer structure is segmented into distinct regions: the MEMS substrate with diaphragm area, the ASIC wafer, and the oxide layer. The etching process is localized to specific trenches in the MEMS substrate, separated from the ASIC wafer by the protective oxide layer, allowing selective access to the diaphragm area without damaging the ASIC
Solution Approach 2:
The oxide layer serves as an intermediary protective barrier between the gas phase etching process and the ASIC wafer. This intermediate layer allows the etching to reach the diaphragm area through defined trenches while preventing the harmful etching gas from contacting and damaging the ASIC wafer and wafer edge
2Ease of manufacture
If the oxide layer is removed to enable media access, then access to the diaphragm area is achieved, but the diaphragm becomes vulnerable to environmental effects
Solution Approach 1:
The oxide layer is selectively removed only in specific trenches where media access is required, while the oxide layer remains intact in other areas to protect the diaphragm. This localized removal allows media access to the diaphragm area through defined pathways while maintaining environmental protection in surrounding regions
3Manufacturing precision
If a backside port is used for media access, then the media access point can be created, but the process becomes complex with multiple etching steps
Solution Approach 1:
The etching trenches for media access are created during the preliminary stages of wafer fabrication, before the ASIC wafer is bonded to the MEMS substrate. This preliminary action allows the media access pathways to be pre-formed in the MEMS substrate, simplifying subsequent assembly steps and reducing overall process 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 method effectively protects the sensitive diaphragm area from environmental effects, simplifies the manufacturing process, and avoids the need for technically complex side ports, while enabling the integration of pressure sensors with inertial sensors, reducing the risk of electrical short circuits and mechanical stress.
Implementation Method 1
bonding the MEMS wafer to the cap wafer
Implementation Method 2
forming a media access point to the diaphragm area by grinding the MEMS substrate
Data Source
AI summary
A method for manufacturing a micromechanical sensor, including the steps: providing a MEMS wafer that includes a MEMS substrate, a defined number of etching trenches being formed in the MEMS substrate in a diaphragm area, the diaphragm area being formed in a first silicon layer that is situated at a defined distance from the MEMS substrate; providing a cap wafer; bonding the MEMS wafer to the cap wafer; and forming a media access point to the diaphragm area by grinding the MEMS substrate.