MEMS Sensor Cavity Formation via Chemical Etching
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Solution Overview
Problem
Existing MEMS pressure sensor chip cavity formation methods, such as grinding and SOI wafer approaches, result in membrane thicknesses greater than 10 μm and high costs, necessitating a more cost-effective and precise method for thinning the membrane.
Innovation Solution
A method involving forming a groove in a substrate, bonding a covering layer to create a cavity, and using etching techniques, specifically wet-chemical etching, to thin the covering layer to less than 10 μm, potentially below 5 μm, without removing silicon layers, allowing for precise control of membrane thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If grinding method is used to form cavity, then membrane thickness can be reduced, but membrane thickness remains over 10 μm due to grinding processing limitations
Solution Approach 1:
The patent replaces the mechanical grinding process with a chemical etching process to thin the membrane. Instead of using mechanical abrasion to remove material, the invention employs chemical reactions to selectively remove material from the membrane, achieving thinner and more precise thickness control that cannot be obtained through grinding alone.
Solution Approach 2:
The patent changes the processing method from mechanical to chemical, and adjusts etching parameters such as etching time, temperature, and chemical composition to precisely control the membrane thickness. This allows achieving membrane thickness below 10 μm with high precision that is not attainable through mechanical grinding.
2Length of moving object
If SOI wafer approach is used to form cavity, then thinner membrane structure can be obtained, but manufacturing cost increases significantly
Solution Approach 1:
The patent uses standard silicon wafers instead of expensive SOI wafers. The covering layer is bonded to the substrate and then etched to create the thin membrane structure, achieving the same thin membrane result without requiring costly SOI substrate materials.
Solution Approach 2:
The patent extracts only the necessary functional layer (the covering layer) to form the thin membrane, rather than using a pre-fabricated SOI wafer with multiple layers. By bonding a separate covering layer and selectively etching it, the invention obtains the thin membrane structure while eliminating the need for expensive SOI substrate materials.
3Ease of manufacture
If covering layer is bonded and ground to thin thickness, then cavity can be formed, but membrane thickness is limited to over 10 μm
Solution Approach 1:
The patent replaces the mechanical grinding step with a chemical etching step after bonding the covering layer. Instead of relying on mechanical removal that is limited to thicknesses over 10 μm, the invention uses chemical etching to achieve much thinner membrane depths that are not achievable through grinding alone.
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 formation of thinner, more stable membranes with high sensing performance at a lower cost compared to traditional methods, maintaining sensitivity and stability while avoiding the high expense of SOI wafers.
Implementation Method 1
bonding the covering layer onto the substrate through a fusion bonding
Implementation Method 2
wet-etching the covering layer. Preferably, the wet-etching includes a chemical etching
Data Source
AI summary
A method for forming a cavity of a sensor chip. The method comprises forming a first groove (a2) on a substrate (a1); bonding a covering layer (a4) onto the substrate (a1) to cover the first groove (a2), thereby forming a cavity; and etching the covering layer (a4) to decrease a thickness of the covering layer. The method can implement a thinner thickness of a film, thereby improving the sensitivity of a sensor.