MEMS Sensor Structure Using Silicon-on-Insulator Substrate
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Solution Overview
Problem
Conventional MEMS devices on glass substrates face limitations in thickness reduction due to glass polishing technology, require additional protective oxide and metal layers for conductive lines, and have uncontrolled component thickness variations during etching processes, leading to high costs and reduced stability and reliability.
Innovation Solution
A structure and fabrication process using a silicon substrate chip with insulating layers, air trenches, and conductive patterns to connect anchor and sensor components, eliminating the need for thin conductive wires and simplifying the fabrication process by integrating a silicon-on-insulator wafer and reducing the number of required masks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If glass substrate is used in conventional MEMS devices, then the device structure is simple, but the thickness cannot be reduced due to limitations of glass polishing technology
Solution Approach 1:
The patent changes the substrate material from glass to silicon, fundamentally altering the material parameter to enable thickness reduction. The silicon substrate allows for much thinner designs (can be reduced to tens of micrometers) compared to glass substrates, which are limited by polishing technology to a minimum thickness of several hundred micrometers.
Solution Approach 2:
The patent employs a silicon-on-insulator (SOI) structure consisting of a silicon substrate with a buried oxide layer. This composite material approach combines the mechanical properties of silicon with the electrical insulation of oxide, enabling both thickness reduction and simplified processing by eliminating the need for separate protective oxide layers.
2Device complexity
If thin conductive lines are disposed between glass substrate and anchor components, then the device structure is compact, but additional protective oxide layer and metal contact layer are required
Solution Approach 1:
The patent extracts and eliminates the protective oxide layer and metal contact layer from the conventional structure. By using the silicon substrate directly as the base for conductive lines, the need for these additional protective layers is removed, simplifying the device structure while maintaining reliability through the inherent stability of the silicon substrate.
Solution Approach 2:
The silicon substrate serves multiple functions simultaneously: it provides mechanical support, electrical insulation (through the buried oxide layer), and a stable base for conductive lines. This multi-functionality eliminates the need for separate protective and contact layers, reducing overall device complexity.
3Manufacturing precision
If etching process is used to form components in conventional MEMS devices, then the fabrication process is established, but variation of component thickness is uncontrolled
Solution Approach 1:
The patent performs preliminary thickness control during the silicon-on-insulator wafer fabrication process, where the silicon layer thickness is precisely controlled before the MEMS device is actually manufactured. This preliminary action ensures uniform component thickness throughout the device, eliminating thickness variation issues that would otherwise occur during subsequent etching processes.
4Reliability
If additional protective oxide layer and metal contact layer are disposed in conventional MEMS devices, then conductive lines are protected, but bonding area is hardly improved
Solution Approach 1:
The patent removes the protective oxide layer and metal contact layer from the conventional structure, eliminating the space these layers occupy. This extraction increases the available bonding area on the substrate surface, allowing for larger bonding regions and improved device integration while maintaining conductive line stability through the silicon substrate itself.
Data Source
AI summary
A structure and a process for a microelectromechanical system (MEMS)-based sensor are provided. The structure for a MEMS-based sensor includes a substrate chip. A first insulating layer covers a top surface of the substrate chip. A device layer is disposed on a top surface of the first insulating layer. The device layer includes a periphery region and a sensor component region. The periphery region and a sensor component region have an air trench therebetween. The component region includes an anchor component and a moveable component. A second insulating layer is disposed on a top surface of the device layer, bridging the periphery region and a portion of the anchor component. A conductive pattern is disposed on the second insulating layer, electrically connecting to the anchor component.